Scientist
01-10-2007, 11:36
Hello
In this thread you can find a great number of animals with description
Good luck
:rambo:
In this thread you can find a great number of animals with description
Good luck
:rambo:
مشاهده نسخه کامل
: The Complete List Of Animals
Scientist
01-10-2007, 11:42
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The unusual mammal called the aardvark was named by South Africans in the early 19th century. In the local language, Afrikaans, “aardvark” means “earth pig.” This name aptly describes a large, heavily built animal with thin hair and short, stumpy legs. The aardvark can reach a length of 6 feet (1.8 meters). Its head has huge donkeylike ears, a long snout, and drooping eyelids with long lashes
Aardvarks, which are also called ant bears, live in dry places in Africa south of the Sahara Desert. During the day they sleep in underground burrows. At night they dig underground for their favorite food, termites. Aardvarks use their sensitive snouts to detect these insects. They break open the termites' nests with their massive, flattened claws and suck up the insects with their long tongues. Although they are not aggressive animals, aardvarks can defend themselves by lashing out with their claws. They can also dig very quickly to bury themselves
Female aardvarks give birth to one baby per year. After a few weeks the baby begins to follow its mother around. It feeds and travels with her for about six months until it becomes more independent.
Scientists classify aardvarks in a group called the Tubulidentata, meaning “tube-toothed.” The tubular teeth have no enamel or roots. The scientific name of the aardvark is Orycterops afer
The unusual mammal called the aardvark was named by South Africans in the early 19th century. In the local language, Afrikaans, “aardvark” means “earth pig.” This name aptly describes a large, heavily built animal with thin hair and short, stumpy legs. The aardvark can reach a length of 6 feet (1.8 meters). Its head has huge donkeylike ears, a long snout, and drooping eyelids with long lashes
Aardvarks, which are also called ant bears, live in dry places in Africa south of the Sahara Desert. During the day they sleep in underground burrows. At night they dig underground for their favorite food, termites. Aardvarks use their sensitive snouts to detect these insects. They break open the termites' nests with their massive, flattened claws and suck up the insects with their long tongues. Although they are not aggressive animals, aardvarks can defend themselves by lashing out with their claws. They can also dig very quickly to bury themselves
Female aardvarks give birth to one baby per year. After a few weeks the baby begins to follow its mother around. It feeds and travels with her for about six months until it becomes more independent.
Scientists classify aardvarks in a group called the Tubulidentata, meaning “tube-toothed.” The tubular teeth have no enamel or roots. The scientific name of the aardvark is Orycterops afer
Scientist
01-10-2007, 11:44
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The ocean bird called the albatross is known for its ability to fly long distances with very little effort. There are more than a dozen species, or kinds, of albatrosses. They belong to the family of birds called Diomedeidae.
Where albatrosses live
Albatrosses are birds of the open sea. They have no need to visit land except to nest. Most species, including the wandering albatross and the sooty albatross, nest on remote southern islands and fly over the surrounding oceans. Other albatrosses, however, nest on tropical Pacific islands and fly over the North Pacific Ocean.
Physical features
Albatrosses are among the largest of flying birds. They can weigh as much as 25 pounds (11 kilograms). The wandering albatross has a longer wingspread than any other bird, measuring more than 11 feet (3 meters) across. Albatrosses have big heads, stout bills, and webbed toes that are used for flight control as well as for swimming.
Most adult albatrosses have white bodies. The wings may be a combination of black, brown, and white. Young birds are generally darker and take five years or more to develop adult coloring. A few species, such as the black-footed albatross and the sooty albatross, are brown all over. The most colorful part of an albatross is its large yellow bill.
Behavior
Albatrosses use their long wings to soar and glide on air currents. They can stay in the air for hours without flapping their wings. When they get hungry, they land on the water and fish with their bills. Squid is their favorite food, but they catch fish as well. They also eat scraps cast to sea from passing ships. Like other seabirds, albatrosses drink seawater and get rid of excess salt through a special gland. At sea, albatrosses sleep on the surface of the water.
Albatrosses are majestic in the air but clumsy on dry land. They often land heavily, and they have to run and flap their wings to take off. Sailors sometimes call them gooney birds because of their comical movements. Another common nickname for albatrosses is mollymawk, from the Dutch words for “foolish gull.”
Life cycle
Albatrosses nest in groups on remote islands. Males and females attract each other with dances and displays. Once formed, a male-female pair usually breeds together year after year. The female lays a single large egg in a nest on the ground. Both parents tend the egg, which takes an unusually long time—often more than 70 days—to hatch. The parents care for the chick for three to ten months, until it is ready to fly. The young albatross then goes out to sea until it is ready to mate, about 5 to 10 years later. Because the growth process takes so long, population growth among albatrosses is slow. Albatrosses have few natural enemies, however, and may live more than 30 years.
Albatrosses and humans
With their habit of following ships, albatrosses have captured the human imagination for centuries. Superstitious people once associated the birds with the spirits of drowned sailors. Killing an albatross was thought to be bad luck. Nevertheless, the birds were killed in large numbers, often for their feathers and meat.
The ocean bird called the albatross is known for its ability to fly long distances with very little effort. There are more than a dozen species, or kinds, of albatrosses. They belong to the family of birds called Diomedeidae.
Where albatrosses live
Albatrosses are birds of the open sea. They have no need to visit land except to nest. Most species, including the wandering albatross and the sooty albatross, nest on remote southern islands and fly over the surrounding oceans. Other albatrosses, however, nest on tropical Pacific islands and fly over the North Pacific Ocean.
Physical features
Albatrosses are among the largest of flying birds. They can weigh as much as 25 pounds (11 kilograms). The wandering albatross has a longer wingspread than any other bird, measuring more than 11 feet (3 meters) across. Albatrosses have big heads, stout bills, and webbed toes that are used for flight control as well as for swimming.
Most adult albatrosses have white bodies. The wings may be a combination of black, brown, and white. Young birds are generally darker and take five years or more to develop adult coloring. A few species, such as the black-footed albatross and the sooty albatross, are brown all over. The most colorful part of an albatross is its large yellow bill.
Behavior
Albatrosses use their long wings to soar and glide on air currents. They can stay in the air for hours without flapping their wings. When they get hungry, they land on the water and fish with their bills. Squid is their favorite food, but they catch fish as well. They also eat scraps cast to sea from passing ships. Like other seabirds, albatrosses drink seawater and get rid of excess salt through a special gland. At sea, albatrosses sleep on the surface of the water.
Albatrosses are majestic in the air but clumsy on dry land. They often land heavily, and they have to run and flap their wings to take off. Sailors sometimes call them gooney birds because of their comical movements. Another common nickname for albatrosses is mollymawk, from the Dutch words for “foolish gull.”
Life cycle
Albatrosses nest in groups on remote islands. Males and females attract each other with dances and displays. Once formed, a male-female pair usually breeds together year after year. The female lays a single large egg in a nest on the ground. Both parents tend the egg, which takes an unusually long time—often more than 70 days—to hatch. The parents care for the chick for three to ten months, until it is ready to fly. The young albatross then goes out to sea until it is ready to mate, about 5 to 10 years later. Because the growth process takes so long, population growth among albatrosses is slow. Albatrosses have few natural enemies, however, and may live more than 30 years.
Albatrosses and humans
With their habit of following ships, albatrosses have captured the human imagination for centuries. Superstitious people once associated the birds with the spirits of drowned sailors. Killing an albatross was thought to be bad luck. Nevertheless, the birds were killed in large numbers, often for their feathers and meat.
Scientist
01-10-2007, 11:49
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Closely related to crocodiles, alligators are large lizard-like animals with long, rounded snouts and powerful tails. They are found in only two countries, the United States and China.
Where alligators live
Only two species of alligator exist on Earth. The larger of the two species is the American alligator. The scientific name of the American alligator is Alligator mississippiensis. It is found in the southeastern United States from North Carolina to Florida and west to the lower Rio Grande. The Chinese alligator (A. sinensis) lives in China in the Yangtze River and its tributaries.
Alligators usually live in slow-moving rivers. They also live along the edges of large bodies of water, such as lakes and swamps. Large adults can stay underwater for over an hour without breathing. Alligators do not have salt glands to remove salt from their body. Because of this, they cannot stay in salty water, such as the ocean, for long.
Although alligators are most comfortable in the water, they are also able to travel on land by sliding on their bellies, stepping with their legs extended, or galloping awkwardly. Alligators dig burrows to escape from danger. They also sleep in these burrows through the winter.
Physical features
The male American alligator grows to an average length of 11 feet (3.4 meters) and can weigh about half a ton. The female American alligator can grow up to 8 feet (2.5 meters). Young American alligators are black with yellow banding on the tail. The adults are brown with dark stripes on the tail.
The Chinese alligator normally grows to a length of 5 feet (1.5 meters). It is blackish with faint yellowish markings.
Alligators have a thick skin composed of close-set, overlapping bony plates called scutes, or osteoderms. They have four short legs. The front legs have five toes, but the back legs have only four. Alligators swim with snakelike movements. Their flat, muscular, oarlike tails provide powerful swimming strokes and are effective weapons as well. Their eyes, ears, and nostrils are located on top of their long head. These can be spotted above the water when alligators are floating at the surface, as they often do.
Although they resemble crocodiles, alligators display some distinctive features. Alligators have a rounded snout, while the snout of most crocodiles is narrow and pointed. When alligators close their jaws none of their teeth can be seen because the fourth tooth in the lower jaw fits into a socket in the upper jaw. The fourth tooth of crocodiles always sticks out at the side of their mouth.
Behavior
Like crocodiles, alligators are basically carnivores, meaning that they eat meat. Young alligators eat worms and insects. As they mature, they add frogs, tadpoles, and fish to their diet. Adult alligators feed mainly on fish, small mammals, and birds, but they may sometimes kill prey as large as deer or cattle. They hunt mainly in water by swallowing their small prey whole. Larger animals are dragged underwater, drowned, and then eaten.
Life cycle
At the time of mating, which is usually in the spring, male alligators give bellowing roars. These roars help establish breeding territories and attract the females. When the time comes to lay eggs, the female builds a mound nest of mud and grass. In this nest, she lays from 20 to 60 hard-shelled, oval, white eggs. They are ready to hatch after about 65 days.
At hatching time the baby alligators start making feeble squeaks. The mother digs the eggs out of the nest. The babies are born with a sharp spike on their noses that they use to break their way through the eggshell. Mother alligators are noted for taking good care of their young. They stay around to protect the eggs and guard the young for as long as a year.
Newborn alligators are about 8 to 10 inches (20 to 25 centimeters) long and face danger from many predators, including fish, birds, and larger alligators. They grow about 1 foot (0.3 meter) in length per year for the first three to four years. After that time, their growth continues more slowly.
Ecological issues
Both the American and Chinese alligator have been killed for their hide, or skin. Their hide is used as leather for handbags, luggage, shoes, belts, and other items. They have also been hunted in order to protect domestic animals and humans. The young of the American alligator have been sold in large numbers as pets. Because of these things, the American alligator has disappeared from many areas where it was once abundant.
The Chinese alligator has become so scarce that it is considered endangered by the International Union for Conservation of Nature and Natural Resources (IUCN).
Closely related to crocodiles, alligators are large lizard-like animals with long, rounded snouts and powerful tails. They are found in only two countries, the United States and China.
Where alligators live
Only two species of alligator exist on Earth. The larger of the two species is the American alligator. The scientific name of the American alligator is Alligator mississippiensis. It is found in the southeastern United States from North Carolina to Florida and west to the lower Rio Grande. The Chinese alligator (A. sinensis) lives in China in the Yangtze River and its tributaries.
Alligators usually live in slow-moving rivers. They also live along the edges of large bodies of water, such as lakes and swamps. Large adults can stay underwater for over an hour without breathing. Alligators do not have salt glands to remove salt from their body. Because of this, they cannot stay in salty water, such as the ocean, for long.
Although alligators are most comfortable in the water, they are also able to travel on land by sliding on their bellies, stepping with their legs extended, or galloping awkwardly. Alligators dig burrows to escape from danger. They also sleep in these burrows through the winter.
Physical features
The male American alligator grows to an average length of 11 feet (3.4 meters) and can weigh about half a ton. The female American alligator can grow up to 8 feet (2.5 meters). Young American alligators are black with yellow banding on the tail. The adults are brown with dark stripes on the tail.
The Chinese alligator normally grows to a length of 5 feet (1.5 meters). It is blackish with faint yellowish markings.
Alligators have a thick skin composed of close-set, overlapping bony plates called scutes, or osteoderms. They have four short legs. The front legs have five toes, but the back legs have only four. Alligators swim with snakelike movements. Their flat, muscular, oarlike tails provide powerful swimming strokes and are effective weapons as well. Their eyes, ears, and nostrils are located on top of their long head. These can be spotted above the water when alligators are floating at the surface, as they often do.
Although they resemble crocodiles, alligators display some distinctive features. Alligators have a rounded snout, while the snout of most crocodiles is narrow and pointed. When alligators close their jaws none of their teeth can be seen because the fourth tooth in the lower jaw fits into a socket in the upper jaw. The fourth tooth of crocodiles always sticks out at the side of their mouth.
Behavior
Like crocodiles, alligators are basically carnivores, meaning that they eat meat. Young alligators eat worms and insects. As they mature, they add frogs, tadpoles, and fish to their diet. Adult alligators feed mainly on fish, small mammals, and birds, but they may sometimes kill prey as large as deer or cattle. They hunt mainly in water by swallowing their small prey whole. Larger animals are dragged underwater, drowned, and then eaten.
Life cycle
At the time of mating, which is usually in the spring, male alligators give bellowing roars. These roars help establish breeding territories and attract the females. When the time comes to lay eggs, the female builds a mound nest of mud and grass. In this nest, she lays from 20 to 60 hard-shelled, oval, white eggs. They are ready to hatch after about 65 days.
At hatching time the baby alligators start making feeble squeaks. The mother digs the eggs out of the nest. The babies are born with a sharp spike on their noses that they use to break their way through the eggshell. Mother alligators are noted for taking good care of their young. They stay around to protect the eggs and guard the young for as long as a year.
Newborn alligators are about 8 to 10 inches (20 to 25 centimeters) long and face danger from many predators, including fish, birds, and larger alligators. They grow about 1 foot (0.3 meter) in length per year for the first three to four years. After that time, their growth continues more slowly.
Ecological issues
Both the American and Chinese alligator have been killed for their hide, or skin. Their hide is used as leather for handbags, luggage, shoes, belts, and other items. They have also been hunted in order to protect domestic animals and humans. The young of the American alligator have been sold in large numbers as pets. Because of these things, the American alligator has disappeared from many areas where it was once abundant.
The Chinese alligator has become so scarce that it is considered endangered by the International Union for Conservation of Nature and Natural Resources (IUCN).
Scientist
01-10-2007, 11:52
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Allosaurus was a fierce dinosaur that roamed the Earth before the similar but more well-known Tyrannosaurus rex appeared. The name Allosaurus means “other lizard.” This dinosaur had bony ridges above each of its eyes. It also had a ridge of bone running down the center of its face between its eyes to the tip of its snout. Allosaurus is a member of the group of dinosaurs known as theropods. The theropods were meat-eating dinosaurs that walked on their two back legs.
Where and when Allosaurus lived
Allosaurus lived about 163 to 144 million years ago, during the period of the Earth's history known as the Jurassic. Most Allosaurus fossils, or remains, have been found in North America, in Colorado, Utah, New Mexico, Montana, South Dakota, and Wyoming. Remains also have been discovered in Africa and Australia. Allosaurus, like most other dinosaurs, was a land animal. It most likely lived near areas with thick plant life, close to the plant-eating dinosaurs that it preyed upon.
Physical features
Allosaurus was a large dinosaur that stood and walked on its two muscular hind legs. It reached up to 39 feet (12 meters) in length, stood about 15 feet (4.5 meters) tall, and weighed up to 2 tons. The massive head of Allosaurus measured about 3 feet (1 meter) long and was supported by a short, thick neck. Large, open spaces in the skull made its head fairly light. The sharp teeth of Allosaurus were curved and had sawlike edges. They were 2 to 4 inches (5 to 10 centimeters) long. The dinosaur's powerful jaws could open wide to tear off larger chunks of food. Allosaurus had sharp claws on the three toes of each hind foot. It also had long, grasping claws on the three toes of each front foot. These claws grew as long as 6 to 10 inches (15 to 25 centimeters). They helped make the animal's short but strong front legs deadly weapons. The long, heavy tail of Allosaurus may have helped the animal balance itself.
Behavior
Allosaurus was a meat-eating dinosaur that preyed on plant-eating dinosaurs. When it hunted alone, Allosaurus would hide among the thick plants then jump out on its prey. It would grab hold with its long front claws and sink its teeth into the neck of its victim. Some scientists believe that Allosaurus also hunted in packs. Together, a pack of Allosaurus could bring down very large dinosaurs, such as Apatosaurus and Diplodocus. It is possible that Allosaurus was also a scavenger, feeding upon carcasses of dead or dying animals. Scientists believe that Allosaurus reproduced by laying eggs.
Allosaurus was a fierce dinosaur that roamed the Earth before the similar but more well-known Tyrannosaurus rex appeared. The name Allosaurus means “other lizard.” This dinosaur had bony ridges above each of its eyes. It also had a ridge of bone running down the center of its face between its eyes to the tip of its snout. Allosaurus is a member of the group of dinosaurs known as theropods. The theropods were meat-eating dinosaurs that walked on their two back legs.
Where and when Allosaurus lived
Allosaurus lived about 163 to 144 million years ago, during the period of the Earth's history known as the Jurassic. Most Allosaurus fossils, or remains, have been found in North America, in Colorado, Utah, New Mexico, Montana, South Dakota, and Wyoming. Remains also have been discovered in Africa and Australia. Allosaurus, like most other dinosaurs, was a land animal. It most likely lived near areas with thick plant life, close to the plant-eating dinosaurs that it preyed upon.
Physical features
Allosaurus was a large dinosaur that stood and walked on its two muscular hind legs. It reached up to 39 feet (12 meters) in length, stood about 15 feet (4.5 meters) tall, and weighed up to 2 tons. The massive head of Allosaurus measured about 3 feet (1 meter) long and was supported by a short, thick neck. Large, open spaces in the skull made its head fairly light. The sharp teeth of Allosaurus were curved and had sawlike edges. They were 2 to 4 inches (5 to 10 centimeters) long. The dinosaur's powerful jaws could open wide to tear off larger chunks of food. Allosaurus had sharp claws on the three toes of each hind foot. It also had long, grasping claws on the three toes of each front foot. These claws grew as long as 6 to 10 inches (15 to 25 centimeters). They helped make the animal's short but strong front legs deadly weapons. The long, heavy tail of Allosaurus may have helped the animal balance itself.
Behavior
Allosaurus was a meat-eating dinosaur that preyed on plant-eating dinosaurs. When it hunted alone, Allosaurus would hide among the thick plants then jump out on its prey. It would grab hold with its long front claws and sink its teeth into the neck of its victim. Some scientists believe that Allosaurus also hunted in packs. Together, a pack of Allosaurus could bring down very large dinosaurs, such as Apatosaurus and Diplodocus. It is possible that Allosaurus was also a scavenger, feeding upon carcasses of dead or dying animals. Scientists believe that Allosaurus reproduced by laying eggs.
Scientist
01-10-2007, 12:04
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The alpaca belongs to the camel family and resembles the llama, to which it is closely related. The alpaca's Latin (or scientific) name is Lama pacos. It is valued for its wool and reared mainly in South America.
Where alpacas live
The alpaca is found on marshy grounds at altitudes above 13,000 feet (4,000 meters). It is presently found in central and southern Peru and western Bolivia in South America. The Indians of the Andes Mountains of South America began raising the alpaca several thousand years ago.
Physical features
Although the alpaca is a member of the camel family, it does not have a hump. Like the llama, the alpaca is a slender-bodied mammal with a long neck and legs, a short tail, a small head, and large, pointed ears. It stands approximately 35 inches (90 centimeters) high at the shoulder, and weighs 121–143 pounds (55–65 kilograms). Its shaggy coat varies in color from black or brown to gray and tan to pale yellow and, occasionally, white. The alpaca has a natural life span of 15–20 years.
Economic importance
The alpaca is bred mainly for its fine wool, and the animal is normally sheared, or trimmed, every two years. Its wool is lightweight, strong, shiny, warm, and stands up to rain and snow. It is sometimes combined with other fibers to make lightweight suit fabrics. There are two breeds of the alpaca, the huacaya and the suri. The suris provide fine fleeces of about 6 12 pounds (3 kilograms) per animal, and the huacayas give coarser fleeces weighing about 5 12 pounds (2.5 kilograms) per animal. Peru is the leading producer of the wool.
The alpaca belongs to the camel family and resembles the llama, to which it is closely related. The alpaca's Latin (or scientific) name is Lama pacos. It is valued for its wool and reared mainly in South America.
Where alpacas live
The alpaca is found on marshy grounds at altitudes above 13,000 feet (4,000 meters). It is presently found in central and southern Peru and western Bolivia in South America. The Indians of the Andes Mountains of South America began raising the alpaca several thousand years ago.
Physical features
Although the alpaca is a member of the camel family, it does not have a hump. Like the llama, the alpaca is a slender-bodied mammal with a long neck and legs, a short tail, a small head, and large, pointed ears. It stands approximately 35 inches (90 centimeters) high at the shoulder, and weighs 121–143 pounds (55–65 kilograms). Its shaggy coat varies in color from black or brown to gray and tan to pale yellow and, occasionally, white. The alpaca has a natural life span of 15–20 years.
Economic importance
The alpaca is bred mainly for its fine wool, and the animal is normally sheared, or trimmed, every two years. Its wool is lightweight, strong, shiny, warm, and stands up to rain and snow. It is sometimes combined with other fibers to make lightweight suit fabrics. There are two breeds of the alpaca, the huacaya and the suri. The suris provide fine fleeces of about 6 12 pounds (3 kilograms) per animal, and the huacayas give coarser fleeces weighing about 5 12 pounds (2.5 kilograms) per animal. Peru is the leading producer of the wool.
Scientist
04-10-2007, 09:44
Most of the animals known as amphibians can live on land or in the water. The word amphibian comes from a Greek word meaning “living a double life.” Amphibians are vertebrates, or animals with backbones. Amphibians were the first vertebrates to appear on land. The early amphibians were the ancestors of all reptiles, birds, and mammals.
There are three types of amphibians. The first group includes the frogs and toads. The second group consists of the salamanders, including the newts and mud puppies. The third group is made up of wormlike creatures known as caecilians.
Where amphibians live
Amphibians are found all over the world except in very cold or dry regions. They are most common in hot, humid areas such as the tropics. Some adult amphibians live only on land. Other species live only in the water. Most amphibians, however, spend at least part of the time on land and part in the water. They live in the areas between freshwater and dry land or in regions that have plenty of dew and moisture.
Frogs and toads have a very wide range but are most abundant in the tropics. Salamanders mainly live in the regions of the Northern Hemisphere that have warm summers and cold winters. They often live in or near streams and are sometimes found under rocks and logs. Caecilians are found throughout most of the tropics. Most caecilians live underground. Some species live in the water.
Physical characteristics
General features
Most amphibians are relatively small animals. However, they vary greatly in length, from less than 25 inch (1 centimeter) to more than 60 inches (150 centimeters).
Amphibians do not have hair or feathers. The skin absorbs water and oxygen. The skin of most amphibians is moist. In most species, if the skin dries up, the animal soon dies. The animal regularly sheds its upper layer of skin, in a process called molting. The lower layer of the skin often includes mucous glands and poison glands. Mucous helps provide essential moisture to the body. Poison helps the animal defend itself against its natural enemies, such as birds and small mammals. Amphibian poisons rarely harm humans.
The skin's protective properties include the ability to change color. This can help the animal hide from enemies by appearing to be a part of its surroundings. At other times, parts of the amphibian's skin may become brightly colored as a warning for enemies to keep away.
Amphibians usually have flat, wide skulls. Although amphibians have teeth, the frogs, toads, and salamanders do not chew their food. They use their long, flexible tongues to capture their prey, which they then swallow whole.
Frogs and toads
Frogs and toads are tailless. They have large, well-developed eyes. They have short, thick bodies and four legs. Frogs have long, powerful hind legs that are well adapted for leaping and swimming. Tree frogs have suction pads on their fingers and toes so that they can hold on to smooth surfaces. Toads have shorter legs than frogs, and they get around by hopping or walking instead of leaping. The skin of toads has a warty appearance and is usually dry.
The West African goliath frog is the largest of this group. It may grow to nearly 1 foot (30 centimeters) long and weigh as much as a house cat. The smallest is a Brazilian species that is less than 25 inch (1 centimeter) long.
Salamanders
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Salamanders have tails. In newts, the tail is flattened. Salamanders generally have short bodies, four legs, and moist skin. They are often boldly patterned or brightly colored. Salamanders have great powers of regeneration. If a salamander loses an eye, a leg, or its tail, it can grow a new one. Most salamanders are about 4 to 6 inches (10 to 15 centimeters) long. However, the Chinese giant salamander grows to 5 feet (1.5 meters) in length. A tiny species in Mexico measures only about 1 inch (2.5 centimeters) long.
Caecilians
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Caecilians look like worms or snakes. They are well adapted for tunneling underground. The long, slender body is encircled by numerous grooves. The caecilian generally has a short, pointed tail. The eyes are covered by skin or bone, so the animals are blind or nearly blind. Near each eye is a tentacle, which the caecilian uses to feel its way around. Caecilian species range in length from about 4 inches (10 centimeters) to nearly 5 feet (1.5 meters).
Behavior
Amphibians are cold-blooded, meaning their body temperature is about the same as the temperature around them. When the temperature drops or rises, amphibians change habitats in order to become more comfortable. A drop in the humidity levels can also affect them.
Some species of amphibians are active by day, and others move about at night. If it becomes too hot and dry, some amphibians become inactive until conditions are favorable again. This is called estivation. Some amphibians become inactive during winter if the region is very cold. They seek out mud, trees, and other safe places in which they remain inactive for months, until it is warm enough again. This is called hibernation.
Frogs and toads have a strong sense of location. When taken from their territories, they can find their way back by smell and instinctively by the position of the stars. Many species tend to return to the same breeding grounds year after year.
Adult amphibians consume a wide variety of foods. Frogs, toads, and salamanders feed mainly on small boneless animals such as insects, worms, and spiders. Some large salamanders and frogs eat small birds and mammals. Salamanders eat members of their own species as well. Earthworms form the main diet of caecilians that live underground. Caecilians that live in water eat fish and eels.
Life cycle
The majority of amphibians lay eggs, but some species give birth to live young. In most egg-laying species, the female deposits a large number of eggs in the water. The tiger salamander may lay more than 5,000 eggs, and the large bullfrogs may lay 45,000 eggs. In some species, the eggs develop and hatch on land. These amphibians come out of the egg as miniature adults.
The life cycle of most amphibians is divided into two phases. In the first phase, the amphibian exists in the water in an immature form called the larva. In frogs and toads, the larva is also known as a tadpole. The larva begins life with gills, which allow it to breathe underwater like a fish. The larva stage lasts from several weeks to as long as five years, depending on the species.
In the second phase, the larva develops into the adult form, capable of existing on land at least part of the time. The lungs develop, and the gill slits close. The period of transformation from larva to adult is known as metamorphosis. Metamorphosis brings about an abrupt and thorough change in the amphibian's form.
Conservation
Humans are the most serious threat to amphibians. Amphibians help keep insect populations under control. However, amphibians are often destroyed when people drain marshes to kill mosquitoes and other insect pests. Pollution can also destroy the places where amphibians live. Amphibians are eaten in some countries. Frog legs are considered a delicacy. Also, many amphibians are used in scientific experiments. Many species of amphibians throughout the world have died out or are in danger of dying out.
There are three types of amphibians. The first group includes the frogs and toads. The second group consists of the salamanders, including the newts and mud puppies. The third group is made up of wormlike creatures known as caecilians.
Where amphibians live
Amphibians are found all over the world except in very cold or dry regions. They are most common in hot, humid areas such as the tropics. Some adult amphibians live only on land. Other species live only in the water. Most amphibians, however, spend at least part of the time on land and part in the water. They live in the areas between freshwater and dry land or in regions that have plenty of dew and moisture.
Frogs and toads have a very wide range but are most abundant in the tropics. Salamanders mainly live in the regions of the Northern Hemisphere that have warm summers and cold winters. They often live in or near streams and are sometimes found under rocks and logs. Caecilians are found throughout most of the tropics. Most caecilians live underground. Some species live in the water.
Physical characteristics
General features
Most amphibians are relatively small animals. However, they vary greatly in length, from less than 25 inch (1 centimeter) to more than 60 inches (150 centimeters).
Amphibians do not have hair or feathers. The skin absorbs water and oxygen. The skin of most amphibians is moist. In most species, if the skin dries up, the animal soon dies. The animal regularly sheds its upper layer of skin, in a process called molting. The lower layer of the skin often includes mucous glands and poison glands. Mucous helps provide essential moisture to the body. Poison helps the animal defend itself against its natural enemies, such as birds and small mammals. Amphibian poisons rarely harm humans.
The skin's protective properties include the ability to change color. This can help the animal hide from enemies by appearing to be a part of its surroundings. At other times, parts of the amphibian's skin may become brightly colored as a warning for enemies to keep away.
Amphibians usually have flat, wide skulls. Although amphibians have teeth, the frogs, toads, and salamanders do not chew their food. They use their long, flexible tongues to capture their prey, which they then swallow whole.
Frogs and toads
Frogs and toads are tailless. They have large, well-developed eyes. They have short, thick bodies and four legs. Frogs have long, powerful hind legs that are well adapted for leaping and swimming. Tree frogs have suction pads on their fingers and toes so that they can hold on to smooth surfaces. Toads have shorter legs than frogs, and they get around by hopping or walking instead of leaping. The skin of toads has a warty appearance and is usually dry.
The West African goliath frog is the largest of this group. It may grow to nearly 1 foot (30 centimeters) long and weigh as much as a house cat. The smallest is a Brazilian species that is less than 25 inch (1 centimeter) long.
Salamanders
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Salamanders have tails. In newts, the tail is flattened. Salamanders generally have short bodies, four legs, and moist skin. They are often boldly patterned or brightly colored. Salamanders have great powers of regeneration. If a salamander loses an eye, a leg, or its tail, it can grow a new one. Most salamanders are about 4 to 6 inches (10 to 15 centimeters) long. However, the Chinese giant salamander grows to 5 feet (1.5 meters) in length. A tiny species in Mexico measures only about 1 inch (2.5 centimeters) long.
Caecilians
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Caecilians look like worms or snakes. They are well adapted for tunneling underground. The long, slender body is encircled by numerous grooves. The caecilian generally has a short, pointed tail. The eyes are covered by skin or bone, so the animals are blind or nearly blind. Near each eye is a tentacle, which the caecilian uses to feel its way around. Caecilian species range in length from about 4 inches (10 centimeters) to nearly 5 feet (1.5 meters).
Behavior
Amphibians are cold-blooded, meaning their body temperature is about the same as the temperature around them. When the temperature drops or rises, amphibians change habitats in order to become more comfortable. A drop in the humidity levels can also affect them.
Some species of amphibians are active by day, and others move about at night. If it becomes too hot and dry, some amphibians become inactive until conditions are favorable again. This is called estivation. Some amphibians become inactive during winter if the region is very cold. They seek out mud, trees, and other safe places in which they remain inactive for months, until it is warm enough again. This is called hibernation.
Frogs and toads have a strong sense of location. When taken from their territories, they can find their way back by smell and instinctively by the position of the stars. Many species tend to return to the same breeding grounds year after year.
Adult amphibians consume a wide variety of foods. Frogs, toads, and salamanders feed mainly on small boneless animals such as insects, worms, and spiders. Some large salamanders and frogs eat small birds and mammals. Salamanders eat members of their own species as well. Earthworms form the main diet of caecilians that live underground. Caecilians that live in water eat fish and eels.
Life cycle
The majority of amphibians lay eggs, but some species give birth to live young. In most egg-laying species, the female deposits a large number of eggs in the water. The tiger salamander may lay more than 5,000 eggs, and the large bullfrogs may lay 45,000 eggs. In some species, the eggs develop and hatch on land. These amphibians come out of the egg as miniature adults.
The life cycle of most amphibians is divided into two phases. In the first phase, the amphibian exists in the water in an immature form called the larva. In frogs and toads, the larva is also known as a tadpole. The larva begins life with gills, which allow it to breathe underwater like a fish. The larva stage lasts from several weeks to as long as five years, depending on the species.
In the second phase, the larva develops into the adult form, capable of existing on land at least part of the time. The lungs develop, and the gill slits close. The period of transformation from larva to adult is known as metamorphosis. Metamorphosis brings about an abrupt and thorough change in the amphibian's form.
Conservation
Humans are the most serious threat to amphibians. Amphibians help keep insect populations under control. However, amphibians are often destroyed when people drain marshes to kill mosquitoes and other insect pests. Pollution can also destroy the places where amphibians live. Amphibians are eaten in some countries. Frog legs are considered a delicacy. Also, many amphibians are used in scientific experiments. Many species of amphibians throughout the world have died out or are in danger of dying out.
Scientist
04-10-2007, 09:50
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An anaconda is a giant water-loving snake that is found in tropical South America. It is one of the two largest snakes in the world. There are stories of giant anacondas reaching more than 50 feet (15 meters) in length. Disappearances of people in the jungles of South America are often blamed on the snakes. However, scientists believe such long lengths are exaggerated and that human deaths by anacondas are rare.
Physical features
The largest anacondas reach about 30 feet (9 meters) in length, but most only grow to about 16 feet (5 meters). Only certain pythons grow longer. Anacondas are, however, the most massive snakes, and many people consider them the world's largest because of both their great weight and length. Some weigh 550 pounds (249 kilograms) and have thick, bulky bodies measuring 12 inches (30 centimeters) or more around.
Types of anacondas
There are two types of anacondas, the giant, or green, anaconda and the yellow anaconda. The largest is the giant anaconda. It lives in or near the water of slow-moving rivers and streams in the rain forests of northeastern South America and on the Caribbean island of Trinidad. The giant anaconda is typically brown or olive green in color and spotted with large, black, oval patches. The yellow anaconda lives further south. Its skin is tan or greenish yellow with black, overlapping spots across its back. Both types have eyes and nostrils on the top of the head, which allow the animal to see and breathe while lying hidden in water or mud.
Hunting habits
Anacondas usually hunt at night for mammals, reptiles, and birds. They are known to hunt animals as large as a young deer, but they usually do not try to capture an animal weighing more than 50 pounds (23 kilograms). The snake hunts by surprising its prey. It quickly coils its body around the animal and squeezes until the animal can no longer breathe. Sometimes the anaconda pulls its prey under water and drowns it. It may also crawl on land and even climb into trees to capture birds.
Life cycle
Female anacondas give birth to large litters. A typical litter has 14–82 young that each measure more than 2 feet (0.6 meter) long. Many of these young become prey for other animals. In captivity, anacondas may survive up to about 30 years.
An anaconda is a giant water-loving snake that is found in tropical South America. It is one of the two largest snakes in the world. There are stories of giant anacondas reaching more than 50 feet (15 meters) in length. Disappearances of people in the jungles of South America are often blamed on the snakes. However, scientists believe such long lengths are exaggerated and that human deaths by anacondas are rare.
Physical features
The largest anacondas reach about 30 feet (9 meters) in length, but most only grow to about 16 feet (5 meters). Only certain pythons grow longer. Anacondas are, however, the most massive snakes, and many people consider them the world's largest because of both their great weight and length. Some weigh 550 pounds (249 kilograms) and have thick, bulky bodies measuring 12 inches (30 centimeters) or more around.
Types of anacondas
There are two types of anacondas, the giant, or green, anaconda and the yellow anaconda. The largest is the giant anaconda. It lives in or near the water of slow-moving rivers and streams in the rain forests of northeastern South America and on the Caribbean island of Trinidad. The giant anaconda is typically brown or olive green in color and spotted with large, black, oval patches. The yellow anaconda lives further south. Its skin is tan or greenish yellow with black, overlapping spots across its back. Both types have eyes and nostrils on the top of the head, which allow the animal to see and breathe while lying hidden in water or mud.
Hunting habits
Anacondas usually hunt at night for mammals, reptiles, and birds. They are known to hunt animals as large as a young deer, but they usually do not try to capture an animal weighing more than 50 pounds (23 kilograms). The snake hunts by surprising its prey. It quickly coils its body around the animal and squeezes until the animal can no longer breathe. Sometimes the anaconda pulls its prey under water and drowns it. It may also crawl on land and even climb into trees to capture birds.
Life cycle
Female anacondas give birth to large litters. A typical litter has 14–82 young that each measure more than 2 feet (0.6 meter) long. Many of these young become prey for other animals. In captivity, anacondas may survive up to about 30 years.
Scientist
04-10-2007, 09:52
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Some people enjoy eating the small fish known as anchovies. Their salty taste can add to the flavor of pizza, salads, and other dishes. Likewise, many larger fish find anchovies tasty. Anchovies make good bait for catching such fish as tuna, sturgeon, and salmon.
Anchovies belong to the scientific family Engraulidae. Most of the more than 100 species, or types, live in saltwater. A few tropical anchovies live in freshwater. Anchovies travel in groups called schools. They come to the water's surface at night to feed on tiny plants and animals known as plankton.
Adult anchovies are about 4 to 10 inches (10 to 25 centimeters) in length. The most noticeable feature of an anchovy is probably its large mouth. The mouth almost always extends behind the eye. An anchovy also has large eyes and a pointed snout.
A female anchovy can lay thousands of eggs each year. The eggs are long and transparent (see-through). They float for about two days before hatching. The newborns, known as larvae, sink to the bottom. The larvae change form to look like adult anchovies after about three months. Anchovies are thought to live as long as seven years.
Some people enjoy eating the small fish known as anchovies. Their salty taste can add to the flavor of pizza, salads, and other dishes. Likewise, many larger fish find anchovies tasty. Anchovies make good bait for catching such fish as tuna, sturgeon, and salmon.
Anchovies belong to the scientific family Engraulidae. Most of the more than 100 species, or types, live in saltwater. A few tropical anchovies live in freshwater. Anchovies travel in groups called schools. They come to the water's surface at night to feed on tiny plants and animals known as plankton.
Adult anchovies are about 4 to 10 inches (10 to 25 centimeters) in length. The most noticeable feature of an anchovy is probably its large mouth. The mouth almost always extends behind the eye. An anchovy also has large eyes and a pointed snout.
A female anchovy can lay thousands of eggs each year. The eggs are long and transparent (see-through). They float for about two days before hatching. The newborns, known as larvae, sink to the bottom. The larvae change form to look like adult anchovies after about three months. Anchovies are thought to live as long as seven years.
Scientist
04-10-2007, 10:04
Stories about legendary animals abounded when much knowledge of the natural world was based on travelers' tales and rumor. An example is The Voyage and Travels of Sir John Mandeville, Knight, written in the mid-14th century, which contained fanciful descriptions of monsters. Even works by scientists contained descriptions of legendary creatures. The Swiss naturalist Conrad Gesner described the unicorn and winged dragons in one book. Some legendary animals, such as the yeti, the Bigfoot, and the Loch Ness monster, still arouse general curiosity.
The most well-known of the legends have appeared in many versions in different works. These include the dragon, various sea serpents, the basilisk, the unicorn, and the phoenix.
Dragon
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The dragon was usually thought of as a huge scaly lizard or snake that breathed fire and had wings like a bat. In Greece the word drakon, from which the English word was derived, was used originally for any large serpent.
In the Middle Eastern world, the serpent or dragon symbolized evil. In Christian art the dragon came to stand for sin. In the Far East, however, the dragon is known as a kind creature. The Chinese dragon represented yang, the principle of heaven, activity, and maleness in Chinese cosmology. From ancient times, it was the emblem of the royal family. Until the 20th century the dragon adorned the Chinese flag.
Sea creatures
Sea serpents were supposed to be enormous snakes, or huge creatures that inhabited the deep sea. Sea serpents have a long history of being sighted by mariners and sailors. Belief in them was widespread throughout the ancient world. Accounts of these fabled creatures might have been based on the sightings of giant squids, which can attain a length of 50 feet (15 meters). Sightings of freshwater “monsters,” especially those in Loch Ness in northern Scotland have been investigated. However, all investigations have been inconclusive. In Norwegian sea folklore, the kraken was an enormous creature, part octopus and part crab. This monster may also be based on chance sightings of the giant squid.
Mermaids were also mythical creatures that lived in the sea. They had the head and upper body of a human being and the tail of a fish. In European folklore, mermaids (sometimes called sirens) and mermen were natural beings who, like fairies, had magical and prophetic powers. Aquatic mammals, such as the dugong and manatee, which suckle their young in human fashion above water, are considered by some to be the basis of these legends.
Basilisk
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The basilisk, or cockatrice, was a serpent so horrible that it killed with a glance. The Roman writer Pliny the Elder described the basilisk simply as a snake with a small golden crown. However, it went on to gain a terrifying reputation. The sight of a basilisk was said to be so dreadful that if the creature saw its own reflection in a mirror, it would die of fright. The only way to kill it, then, was to hold a mirror before it and avoid looking at it directly. In the Middle Ages it was supposed to have the head of a cock, or sometimes a human head.
Unicorn
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The unicorn was a mythological animal resembling a horse or a kid, with a single horn on its forehead. The unicorn appeared in the early artworks of the Mesopotamian civilization. It was also referred to in the ancient myths of India and China.
The earliest description in Greek literature of a single-horned animal was by the historian Ctesias in about 400 BC. The actual animal behind Ctesias' description was probably the Indian rhinoceros. Cups said to be made of unicorn horn, but actually made of rhinoceros horn or narwhal tusk, were highly valued in the Middle Ages as a protection against poisoned drinks.
Phoenix
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Early humans were very interested in birds and attributed magic and religious powers to them. Therefore many mythological creatures, such as thunderbird, phoenix, and roc, have taken the form of birds. In ancient Egypt and in classical antiquity, the phoenix was a fabulous bird associated with the worship of the sun. It was said to be as large as an eagle, with brilliant scarlet and gold feathers. Only one phoenix existed at any one time, and it lived at least 500 years. As its death approached, the phoenix made a nest of boughs and spices, set it on fire, and was consumed in the flames. From the pyre miraculously sprang a new phoenix.
Other creatures
More recent creatures are the Yeti and Bigfoot. The Tibetan yeti was a mythical monster inhabiting the Himalayas at about the level of the snow line. Though reports of actual sightings of such a creature are rare, certain mysterious markings in the snow have traditionally been attributed to it. Bears have probably produced some of these.
A large, hairy creature resembling a human, the Bigfoot is believed by some to exist in northwestern United States and western Canada. It seems to represent the North American counterpart of the yeti. Although some people have claimed to have seen and even photographed the creature, none of the evidence has been verified. Also known as Sasquatch, it is described as ranging from 6 to 15 feet (2 to 4.5 meters) in height, standing erect on two feet, and either moving silently or emitting a high-pitched cry.
The most well-known of the legends have appeared in many versions in different works. These include the dragon, various sea serpents, the basilisk, the unicorn, and the phoenix.
Dragon
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The dragon was usually thought of as a huge scaly lizard or snake that breathed fire and had wings like a bat. In Greece the word drakon, from which the English word was derived, was used originally for any large serpent.
In the Middle Eastern world, the serpent or dragon symbolized evil. In Christian art the dragon came to stand for sin. In the Far East, however, the dragon is known as a kind creature. The Chinese dragon represented yang, the principle of heaven, activity, and maleness in Chinese cosmology. From ancient times, it was the emblem of the royal family. Until the 20th century the dragon adorned the Chinese flag.
Sea creatures
Sea serpents were supposed to be enormous snakes, or huge creatures that inhabited the deep sea. Sea serpents have a long history of being sighted by mariners and sailors. Belief in them was widespread throughout the ancient world. Accounts of these fabled creatures might have been based on the sightings of giant squids, which can attain a length of 50 feet (15 meters). Sightings of freshwater “monsters,” especially those in Loch Ness in northern Scotland have been investigated. However, all investigations have been inconclusive. In Norwegian sea folklore, the kraken was an enormous creature, part octopus and part crab. This monster may also be based on chance sightings of the giant squid.
Mermaids were also mythical creatures that lived in the sea. They had the head and upper body of a human being and the tail of a fish. In European folklore, mermaids (sometimes called sirens) and mermen were natural beings who, like fairies, had magical and prophetic powers. Aquatic mammals, such as the dugong and manatee, which suckle their young in human fashion above water, are considered by some to be the basis of these legends.
Basilisk
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The basilisk, or cockatrice, was a serpent so horrible that it killed with a glance. The Roman writer Pliny the Elder described the basilisk simply as a snake with a small golden crown. However, it went on to gain a terrifying reputation. The sight of a basilisk was said to be so dreadful that if the creature saw its own reflection in a mirror, it would die of fright. The only way to kill it, then, was to hold a mirror before it and avoid looking at it directly. In the Middle Ages it was supposed to have the head of a cock, or sometimes a human head.
Unicorn
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The unicorn was a mythological animal resembling a horse or a kid, with a single horn on its forehead. The unicorn appeared in the early artworks of the Mesopotamian civilization. It was also referred to in the ancient myths of India and China.
The earliest description in Greek literature of a single-horned animal was by the historian Ctesias in about 400 BC. The actual animal behind Ctesias' description was probably the Indian rhinoceros. Cups said to be made of unicorn horn, but actually made of rhinoceros horn or narwhal tusk, were highly valued in the Middle Ages as a protection against poisoned drinks.
Phoenix
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Early humans were very interested in birds and attributed magic and religious powers to them. Therefore many mythological creatures, such as thunderbird, phoenix, and roc, have taken the form of birds. In ancient Egypt and in classical antiquity, the phoenix was a fabulous bird associated with the worship of the sun. It was said to be as large as an eagle, with brilliant scarlet and gold feathers. Only one phoenix existed at any one time, and it lived at least 500 years. As its death approached, the phoenix made a nest of boughs and spices, set it on fire, and was consumed in the flames. From the pyre miraculously sprang a new phoenix.
Other creatures
More recent creatures are the Yeti and Bigfoot. The Tibetan yeti was a mythical monster inhabiting the Himalayas at about the level of the snow line. Though reports of actual sightings of such a creature are rare, certain mysterious markings in the snow have traditionally been attributed to it. Bears have probably produced some of these.
A large, hairy creature resembling a human, the Bigfoot is believed by some to exist in northwestern United States and western Canada. It seems to represent the North American counterpart of the yeti. Although some people have claimed to have seen and even photographed the creature, none of the evidence has been verified. Also known as Sasquatch, it is described as ranging from 6 to 15 feet (2 to 4.5 meters) in height, standing erect on two feet, and either moving silently or emitting a high-pitched cry.
Scientist
04-10-2007, 10:11
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The armored dinosaur known as Ankylosaurus had a tail that ended in a large, bony club. It was one of a family of plant-eating dinosaurs that walked on four legs and was protected by heavy armor. Euoplocephalus was another member of this family.
Where and when Ankylosaurus lived
Ankylosaurus lived 70 to 65 million years ago, during the period of the Earth's history known as the Cretaceous. Many Ankylosaurus fossils, or remains, have been found in North America, mostly in Montana, Wyoming, and in Canada. These dinosaurs lived in areas that were thick with plant life and that often surrounded bodies of water, such as lakes.
Physical features
Ankylosaurus was a stocky dinosaur that reached a length of 25 to 33 feet (7 to 10 meters), weighed up to 4 tons, and stood 4 feet (1.2 meters) tall. This dinosaur had small bony plates covering its entire body. In addition to these plates it had rows of small bony projections on its sides and bony knobs on its back. Ankylosaurus also had hornlike ridges in the upper and lower corners of its skull, just behind its eyes. It had a short, wide head and rather weak beaklike jaws with a few small teeth. Ankylosaurus stood and walked on all four of its sturdy legs. The two back legs were longer than the front two, and its feet were wide and hooflike.
Behavior
Ankylosaurus was a plant eater that fed on soft and pulpy low-growing plants and shrubs. This dinosaur, like other plant-eating dinosaurs, swallowed small stones to help grind the plant material in its stomach. Ankylosaurus was a slow-moving dinosaur. It depended on the bony plates covering its body to protect it from its enemies. The club at the end of its tail was used as a weapon in self-defense. When attacked, Ankylosaurus could swing its tail with a great deal of force. Like most other dinosaurs, Ankylosaurus reproduced by laying eggs.
The armored dinosaur known as Ankylosaurus had a tail that ended in a large, bony club. It was one of a family of plant-eating dinosaurs that walked on four legs and was protected by heavy armor. Euoplocephalus was another member of this family.
Where and when Ankylosaurus lived
Ankylosaurus lived 70 to 65 million years ago, during the period of the Earth's history known as the Cretaceous. Many Ankylosaurus fossils, or remains, have been found in North America, mostly in Montana, Wyoming, and in Canada. These dinosaurs lived in areas that were thick with plant life and that often surrounded bodies of water, such as lakes.
Physical features
Ankylosaurus was a stocky dinosaur that reached a length of 25 to 33 feet (7 to 10 meters), weighed up to 4 tons, and stood 4 feet (1.2 meters) tall. This dinosaur had small bony plates covering its entire body. In addition to these plates it had rows of small bony projections on its sides and bony knobs on its back. Ankylosaurus also had hornlike ridges in the upper and lower corners of its skull, just behind its eyes. It had a short, wide head and rather weak beaklike jaws with a few small teeth. Ankylosaurus stood and walked on all four of its sturdy legs. The two back legs were longer than the front two, and its feet were wide and hooflike.
Behavior
Ankylosaurus was a plant eater that fed on soft and pulpy low-growing plants and shrubs. This dinosaur, like other plant-eating dinosaurs, swallowed small stones to help grind the plant material in its stomach. Ankylosaurus was a slow-moving dinosaur. It depended on the bony plates covering its body to protect it from its enemies. The club at the end of its tail was used as a weapon in self-defense. When attacked, Ankylosaurus could swing its tail with a great deal of force. Like most other dinosaurs, Ankylosaurus reproduced by laying eggs.
Scientist
06-10-2007, 09:59
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Ants are social insects who live in organized colonies. There are some 8,000 different types of ants in the world. They are found almost everywhere, but they are most common in hot areas.
Physical features
Most ants have the same basic physical structure. They range in size from 8100 to 1 inch (2 to 25 millimeters). They are usually yellow, brown, red, or black. The body of an ant is divided into three sections: the head, the thorax, and the abdomen. The head is large, and the abdomen is slender and oval. The thorax, or midsection, is connected to the abdomen by a small waist. The mouth is an important tool for most ants. It consists of two sets of jaws, the outer pair and the inner pair. The jaws are used for fighting, eating, and carrying food and other materials.
Most ants have simple eyes, called ocelli, on top of the head, as well as a compound eye with many lenses on each side of the head. However, their vision is believed to be poor. More useful than the eyes are the antennae. The antennae are located on the top of the head and help in guiding the ant. They also act as an organ of smell and communication.
Life cycle
The life cycle of the ant has four stages: egg, larva, pupa, and adult. The larvae have no eyes or legs. After the larvae hatch out of the eggs, they shed their skin several times. Most of them spin a silken cocoon around their bodies and rest inside while they grow into adults. When a pupa is ready to break out of its cocoon, a nurse ant bites a hole at the end of the silken wrapping and helps the weak little ant free its legs and antennae. Then she washes and feeds it. Most ants live for 6 to 10 weeks, though some live up to 15 years.
Behavior
There are different classes in the social organization of ants: queens, workers, soldiers, and males. The queen spends her life laying eggs. The workers are females and do the work of the nest; the larger females, the soldiers, defend the colony. At certain times of the year, many species produce winged males and queens. They fly into the air, where they mate. The male dies soon afterward, and the fertilized queen establishes a new nest.
Ants are very social creatures. They live in groups called colonies inside a nest. They make their nests out of many materials, including soil, sand, wood, and leaves. Some ants build anthills. The nest is kept very clean. If an ant dies, a worker carries it from the nest to a place that is a cemetery and a garbage dump. If the queen dies, however, the workers continue to care for her as long as her body is unharmed.
Ants are also capable of warlike behavior. Ants have different methods of defense. Some bite or spit out a disagreeable liquid. Others run away when under attack, “play dead,” or send sound signals to warn other members of their colony of danger.
Ants are social insects who live in organized colonies. There are some 8,000 different types of ants in the world. They are found almost everywhere, but they are most common in hot areas.
Physical features
Most ants have the same basic physical structure. They range in size from 8100 to 1 inch (2 to 25 millimeters). They are usually yellow, brown, red, or black. The body of an ant is divided into three sections: the head, the thorax, and the abdomen. The head is large, and the abdomen is slender and oval. The thorax, or midsection, is connected to the abdomen by a small waist. The mouth is an important tool for most ants. It consists of two sets of jaws, the outer pair and the inner pair. The jaws are used for fighting, eating, and carrying food and other materials.
Most ants have simple eyes, called ocelli, on top of the head, as well as a compound eye with many lenses on each side of the head. However, their vision is believed to be poor. More useful than the eyes are the antennae. The antennae are located on the top of the head and help in guiding the ant. They also act as an organ of smell and communication.
Life cycle
The life cycle of the ant has four stages: egg, larva, pupa, and adult. The larvae have no eyes or legs. After the larvae hatch out of the eggs, they shed their skin several times. Most of them spin a silken cocoon around their bodies and rest inside while they grow into adults. When a pupa is ready to break out of its cocoon, a nurse ant bites a hole at the end of the silken wrapping and helps the weak little ant free its legs and antennae. Then she washes and feeds it. Most ants live for 6 to 10 weeks, though some live up to 15 years.
Behavior
There are different classes in the social organization of ants: queens, workers, soldiers, and males. The queen spends her life laying eggs. The workers are females and do the work of the nest; the larger females, the soldiers, defend the colony. At certain times of the year, many species produce winged males and queens. They fly into the air, where they mate. The male dies soon afterward, and the fertilized queen establishes a new nest.
Ants are very social creatures. They live in groups called colonies inside a nest. They make their nests out of many materials, including soil, sand, wood, and leaves. Some ants build anthills. The nest is kept very clean. If an ant dies, a worker carries it from the nest to a place that is a cemetery and a garbage dump. If the queen dies, however, the workers continue to care for her as long as her body is unharmed.
Ants are also capable of warlike behavior. Ants have different methods of defense. Some bite or spit out a disagreeable liquid. Others run away when under attack, “play dead,” or send sound signals to warn other members of their colony of danger.
Scientist
06-10-2007, 10:03
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Among the most curious looking animals in the world are the anteaters. Their long heads and snouts look like tubes, and they have no teeth at all. Their front legs are very strong and armed with heavy, curved claws, which they use to break open the nests of ants and termites. Then, when the insects rush out, they snatch them up with their long, sticky tongues.
Three Species
Anteaters are found in the swamps and forests of Central and South America. There are three species, of which the largest is the giant anteater. The scientific name of the giant anteater is Myrmecophaga tridactyla. Although its body is only about 3 feet (1 meter) long, it measures more than twice that length from the tip of its snout to the end of its long, bushy tail. It weighs about 55 pounds (25 kilograms). Its body is covered with gray hairs, with a band of black across the breast and a white stripe on the shoulders. It spends all its time on the ground, and it may be active both by day and by night. It is not usually a savage animal, but it becomes very fierce if it is cornered. It can do severe damage with the very sharp claws of the forefeet.
The lesser anteater, or tamandua (Tamandua tetradactyla), lives in trees. This species is much smaller than the great anteater, measuring only about half the length. It has a long but not a bushy tail, which helps it to climb on tree branches. Active mainly at night, it feeds chiefly on ants nesting in trees.
The two-toed anteater (Cyclops didactylus) is the smallest of the family. It is the size of a squirrel. Because of the color of its fur it is sometimes called the golden anteater. Like the lesser anteater, the two-toed anteater lives in trees and is most active at night.
The Anteater's Relatives
Various other insect-eating animals are sometimes called anteaters, though they really belong to other groups of animals. One of them is the aardvark, or ant bear. Another is the echidna, or spiny anteater, which is related to the platypus. The pangolin, or scaly anteater, is covered with protective scales. Other relatives of the anteater include the sloth, the armadillo, and the numbat, or banded anteater.
Among the most curious looking animals in the world are the anteaters. Their long heads and snouts look like tubes, and they have no teeth at all. Their front legs are very strong and armed with heavy, curved claws, which they use to break open the nests of ants and termites. Then, when the insects rush out, they snatch them up with their long, sticky tongues.
Three Species
Anteaters are found in the swamps and forests of Central and South America. There are three species, of which the largest is the giant anteater. The scientific name of the giant anteater is Myrmecophaga tridactyla. Although its body is only about 3 feet (1 meter) long, it measures more than twice that length from the tip of its snout to the end of its long, bushy tail. It weighs about 55 pounds (25 kilograms). Its body is covered with gray hairs, with a band of black across the breast and a white stripe on the shoulders. It spends all its time on the ground, and it may be active both by day and by night. It is not usually a savage animal, but it becomes very fierce if it is cornered. It can do severe damage with the very sharp claws of the forefeet.
The lesser anteater, or tamandua (Tamandua tetradactyla), lives in trees. This species is much smaller than the great anteater, measuring only about half the length. It has a long but not a bushy tail, which helps it to climb on tree branches. Active mainly at night, it feeds chiefly on ants nesting in trees.
The two-toed anteater (Cyclops didactylus) is the smallest of the family. It is the size of a squirrel. Because of the color of its fur it is sometimes called the golden anteater. Like the lesser anteater, the two-toed anteater lives in trees and is most active at night.
The Anteater's Relatives
Various other insect-eating animals are sometimes called anteaters, though they really belong to other groups of animals. One of them is the aardvark, or ant bear. Another is the echidna, or spiny anteater, which is related to the platypus. The pangolin, or scaly anteater, is covered with protective scales. Other relatives of the anteater include the sloth, the armadillo, and the numbat, or banded anteater.
Scientist
06-10-2007, 10:07
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Antelopes are plant-eating animals known for their beauty, grace, and speed in running. The impala, gazelle, addax, gnu, and kudu are all antelopes.
Where antelopes live
Antelopes are found on the large grassy plains of Africa and in the central and southwest regions of Eurasia. Only one antelope, the pronghorn or prongbuck, is found in North America.
Physical features
Most antelopes have horns that sweep up and back. Their coats are generally golden, reddish tan, or gray. The face, belly and rump tend to be white. In size, antelopes generally compare with most goats and deer. The largest and tallest antelope is the African giant eland, about 69 inches (175 centimeters) tall at the shoulders and weighing about 1,764 pounds (800 kilograms). The smallest is the African royal, about 10 inches (25 centimeters) tall at the shoulders and weighing only about 6 pounds (2.7 kilograms).
Antelope horns vary greatly in size and shape. The giant sable antelope has huge horns about 63 inches (160 centimeters) long, while the royal has small spikes that are only 1 inch (2.5 centimeters) long. The four-horned antelope of India has two pairs of horns, one on its forehead and a larger pair on the top of its head.
Antelopes have excellent senses of smell and hearing. This helps them to detect danger and leap to safety. Antelopes can run very fast. The pronghorn can run 43 miles (70 kilometers) per hour and leap 20 feet (6 meters). Thomson's gazelle can run 50 miles (80 kilometers) per hour. The impala, known for its great springing leaps, can jump to a height of almost 8 feet (2.4 meters) and cover 33 feet (10 meters) in a bound.
Behavior
Antelopes are herbivores, which means they eat plants and grass. They follow a circular grazing route over a particular area of land and may cover more than 200 square miles (500 square kilometers) in a year. They generally travel in herds of several hundred antelopes. A few live alone—these are usually old or weak animals, males with no mates, or females about to give birth. A doe, or female antelope, returns to the herd once her young are big enough to follow her.
Life cycle
During the mating season, male antelopes mark territories and then attract the attention of passing does. They do this by rubbing their scent glands against plants and trees. A male will defend his territory from other male antelopes by signaling them to fight. In such a case, two males lock their horns together and wrestle in combat. Neither animal comes to any great harm. One antelope, however, the African eland, has been known to fight to the death. The antelope doe may produce her young after four to eight months.
Survival issues
Some types of antelope have been hunted so much that they no longer exist at all. These include the Arabian oryx, giant sable, blesbok, and bontebok. Other antelopes, such as the eland, roan, greater kudu, and waterbuck, are still being hunted. Some antelopes in danger of extinction are being protected in special parks.
Antelopes are plant-eating animals known for their beauty, grace, and speed in running. The impala, gazelle, addax, gnu, and kudu are all antelopes.
Where antelopes live
Antelopes are found on the large grassy plains of Africa and in the central and southwest regions of Eurasia. Only one antelope, the pronghorn or prongbuck, is found in North America.
Physical features
Most antelopes have horns that sweep up and back. Their coats are generally golden, reddish tan, or gray. The face, belly and rump tend to be white. In size, antelopes generally compare with most goats and deer. The largest and tallest antelope is the African giant eland, about 69 inches (175 centimeters) tall at the shoulders and weighing about 1,764 pounds (800 kilograms). The smallest is the African royal, about 10 inches (25 centimeters) tall at the shoulders and weighing only about 6 pounds (2.7 kilograms).
Antelope horns vary greatly in size and shape. The giant sable antelope has huge horns about 63 inches (160 centimeters) long, while the royal has small spikes that are only 1 inch (2.5 centimeters) long. The four-horned antelope of India has two pairs of horns, one on its forehead and a larger pair on the top of its head.
Antelopes have excellent senses of smell and hearing. This helps them to detect danger and leap to safety. Antelopes can run very fast. The pronghorn can run 43 miles (70 kilometers) per hour and leap 20 feet (6 meters). Thomson's gazelle can run 50 miles (80 kilometers) per hour. The impala, known for its great springing leaps, can jump to a height of almost 8 feet (2.4 meters) and cover 33 feet (10 meters) in a bound.
Behavior
Antelopes are herbivores, which means they eat plants and grass. They follow a circular grazing route over a particular area of land and may cover more than 200 square miles (500 square kilometers) in a year. They generally travel in herds of several hundred antelopes. A few live alone—these are usually old or weak animals, males with no mates, or females about to give birth. A doe, or female antelope, returns to the herd once her young are big enough to follow her.
Life cycle
During the mating season, male antelopes mark territories and then attract the attention of passing does. They do this by rubbing their scent glands against plants and trees. A male will defend his territory from other male antelopes by signaling them to fight. In such a case, two males lock their horns together and wrestle in combat. Neither animal comes to any great harm. One antelope, however, the African eland, has been known to fight to the death. The antelope doe may produce her young after four to eight months.
Survival issues
Some types of antelope have been hunted so much that they no longer exist at all. These include the Arabian oryx, giant sable, blesbok, and bontebok. Other antelopes, such as the eland, roan, greater kudu, and waterbuck, are still being hunted. Some antelopes in danger of extinction are being protected in special parks.
Scientist
06-10-2007, 10:10
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A massive dinosaur, the Apatosaurus weighed as much as five adult elephants. The name Apatosaurus means “deceptive lizard.” This dinosaur may be better known by its former name, Brontosaurus, which means “thunder lizard.” It was called this because of the loud, earth-shaking sound it may have made while walking. Apatosaurus belongs to the group of dinosaurs known as sauropods, which also includes Brachiosaurus and Diplodocus. The sauropods were large, plant-eating dinosaurs with long necks, massive bodies, and four pillarlike legs to support the body.
Where and when Apatosaurus lived
Apatosaurus lived about 147 to 137 million years ago, during the late Jurassic and early Cretaceous periods of the Earth's history. Most Apatosaurus remains have been found in North America, particularly in Wyoming, Utah, Oklahoma, and Colorado. It was once believed that Apatosaurus lived in swampy areas because it needed to live in water to support the weight of its heavy body. Modern scientists now agree that Apatosaurus was mainly a land animal. Studies show that its thick legs, elephantlike feet, and strong skeleton were able to support Apatosaurus on land.
Physical features
Apatosaurus was one of the largest land animals of all time. It reached a length of 70 feet (21 meters), weighed 30 to 36 tons, and stood 15 feet (4.6 meters) tall at the hips. This dinosaur also had a very long neck and tail. Apatosaurus was a quadruped, meaning that it stood and walked on all four legs. It had claws on its large feet. Apatosaurus had a small, horselike head that measured only 2 feet (61 centimeters) in length, and long, peg-shaped teeth.
Behavior
Apatosaurus was a plant-eater. It fed on the leaves and needles of sequoia, fir, and pine trees, as well as ferns and other low-lying plants. Its long neck may have enabled Apatosaurus to reach as high as 35 feet (10.6 meters) to browse the treetops. In order to aid digestion, this dinosaur swallowed small stones to help grind up the plants in its stomach. Fossil sites suggest that Apatosaurus lived and traveled together in herds. Like other dinosaurs, Apatosaurus reproduced by laying eggs. Young Apatosaurus did not join the adult herd until they were large enough and weighed about 1 ton. Apatosaurus reached adulthood at about 20 years of age and lived to be about 100 years old.
A massive dinosaur, the Apatosaurus weighed as much as five adult elephants. The name Apatosaurus means “deceptive lizard.” This dinosaur may be better known by its former name, Brontosaurus, which means “thunder lizard.” It was called this because of the loud, earth-shaking sound it may have made while walking. Apatosaurus belongs to the group of dinosaurs known as sauropods, which also includes Brachiosaurus and Diplodocus. The sauropods were large, plant-eating dinosaurs with long necks, massive bodies, and four pillarlike legs to support the body.
Where and when Apatosaurus lived
Apatosaurus lived about 147 to 137 million years ago, during the late Jurassic and early Cretaceous periods of the Earth's history. Most Apatosaurus remains have been found in North America, particularly in Wyoming, Utah, Oklahoma, and Colorado. It was once believed that Apatosaurus lived in swampy areas because it needed to live in water to support the weight of its heavy body. Modern scientists now agree that Apatosaurus was mainly a land animal. Studies show that its thick legs, elephantlike feet, and strong skeleton were able to support Apatosaurus on land.
Physical features
Apatosaurus was one of the largest land animals of all time. It reached a length of 70 feet (21 meters), weighed 30 to 36 tons, and stood 15 feet (4.6 meters) tall at the hips. This dinosaur also had a very long neck and tail. Apatosaurus was a quadruped, meaning that it stood and walked on all four legs. It had claws on its large feet. Apatosaurus had a small, horselike head that measured only 2 feet (61 centimeters) in length, and long, peg-shaped teeth.
Behavior
Apatosaurus was a plant-eater. It fed on the leaves and needles of sequoia, fir, and pine trees, as well as ferns and other low-lying plants. Its long neck may have enabled Apatosaurus to reach as high as 35 feet (10.6 meters) to browse the treetops. In order to aid digestion, this dinosaur swallowed small stones to help grind up the plants in its stomach. Fossil sites suggest that Apatosaurus lived and traveled together in herds. Like other dinosaurs, Apatosaurus reproduced by laying eggs. Young Apatosaurus did not join the adult herd until they were large enough and weighed about 1 ton. Apatosaurus reached adulthood at about 20 years of age and lived to be about 100 years old.
Scientist
06-10-2007, 10:16
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The most humanlike of all animals, the ape is often termed anthropoid, meaning, “resembling a human.” Apes and humans are members of the group of animals called primates. This group also includes monkeys, lemurs, lorises, and tarsiers. The apes are divided into two categories: the lesser apes and the great apes. The lesser apes are the gibbons, and the great apes are the orangutans, chimpanzees, and gorillas.
Where apes live
Apes live in tropical rain forests. Both gibbons and orangutans inhabit the forests of southeastern Asia. Gibbons are found in the mainland and islands, and orangutans are found in the lowland rain forests on the islands of Borneo and Sumatra.
Chimpanzees, bonobos, and gorillas inhabit rain forests that lie on or near the equator in Africa. Chimpanzees, in particular, have a wide geographic range and are found in more than a dozen countries of western and central equatorial Africa. Bonobos, on the other hand, are found only in the lowland rain forests of the Democratic Republic of the Congo in central Africa.
Gibbons and orangutans are arboreal, meaning they live mainly in trees. The orangutan, in fact, is the largest tree-dwelling animal in the world. Sometimes adult male orangutans have to descend to the ground to travel long distances, as the smaller tree branches cannot support their weight. Chimpanzees spend time both on the trees and the ground. Chimpanzees and bonobos come down to the ground to cover larger distances. Most of their feeding otherwise takes place on the trees. Gorillas are largely terrestrial, that is, they spend most of their time on the ground.
Most apes are active during the day. At night they lodge in trees and all except gibbons build sleeping nests for the purpose.
Physical characteristics
Apes share many characteristics, yet each species is quite distinctive in appearance. For instance, all apes have hair, but the color and volume varies from species to species. Gibbons range from tan or silvery to brown or black. Orangutans have a long, reddish-brown coat, or pelage, and are sometimes also called the red ape. Chimpanzees sport a coat of brown or black hair. Gorillas have black skin and hair. The adult male gorilla has a prominent crest on top of the skull and a “saddle” of gray or silver hairs on the lower part of the back. Hence mature males are given the name, silverback.
Gorillas, chimpanzees, and orangutans have short, thickset bodies, long arms, and short legs. Bonobos closely resemble chimpanzees, but have longer arms and a more slender body. Gibbons have remarkably long arms though they are the smallest among apes.
Gorillas are the largest apes. They may attain a height of about 5 12 feet (170 centimeters) and a weight of 300–600 pounds (135–275 kilograms) in the wild.
One feature common to all apes, and which separates them from other primates like monkeys, is that they do not have a tail. Like humans, apes have opposable thumbs and toes, which enable them to grasp and hold objects and to climb. Their fingers and toes have flat nails instead of claws.
Behavior
Movies and books have often portrayed gorillas as ferocious. Studies, however, show that they are not aggressive by nature. Gorillas live in stable family groups of 6 to 20 animals that are led by one or two adult males. The adults are protective towards the other members of the group and turn violent only when they are disturbed or when they sense danger.
Most other apes live in groups as well, though the size of their communities varies. Adult orangutans are the only solitary apes. They come together only for a brief period of courtship before mating.
Apes usually eat shoots, fruits, leaves, seeds, and grass. Gorillas live on an entirely vegetarian diet, but other apes may eat insects, birds' eggs, young birds, or rodents. Bonobos may even eat young antelopes, and chimpanzees sometimes stalk and kill young baboons and bush pigs.
Apes are intelligent creatures, particularly orangutans, gorillas, and chimpanzees. Chimpanzees in the wild use sticks as tools. For instance, they cleverly poke twigs, grass, or other objects into ant and termite nests, withdraw them, and eat the insects that cling to these tools.
Trainers and experimenters have taught both chimpanzees and gorillas to solve problems and use sign language. Orangutans in captivity also show considerable skill and are particularly clever with mechanical objects.
Reproduction and growth
Reproduction among apes is similar to humans. Most apes give birth to a single offspring, after a pregnancy of about seven to nine months. Twins are rare. Infants are generally helpless for the first few months after birth and depend entirely on the mother. They become sexually mature when they are 7 years or older, and may live up to 30 years. It has been noticed that apes generally live longer in captivity.
Under threat
The numbers of most ape species in the wild is shrinking because of hunting and destruction of their natural habitat. Many, like chimpanzees and gorillas, have been exported to zoos and research laboratories. In Africa, gorillas and chimpanzees are prized for their meat. In addition, infant apes bring a high price in the illegal pet trade. These species are considered either vulnerable or endangered.
Steps have been taken for their conservation. Several national parks have been established in countries like Rwanda in Africa and Indonesia and Thailand in southeastern Asia for the protection of gorillas, orangutans, and gibbons. In addition, the law in Indonesia and Malaysia protects the orangutan. The gorilla and bonobos are also protected, but illegal hunting of apes continues.
The most humanlike of all animals, the ape is often termed anthropoid, meaning, “resembling a human.” Apes and humans are members of the group of animals called primates. This group also includes monkeys, lemurs, lorises, and tarsiers. The apes are divided into two categories: the lesser apes and the great apes. The lesser apes are the gibbons, and the great apes are the orangutans, chimpanzees, and gorillas.
Where apes live
Apes live in tropical rain forests. Both gibbons and orangutans inhabit the forests of southeastern Asia. Gibbons are found in the mainland and islands, and orangutans are found in the lowland rain forests on the islands of Borneo and Sumatra.
Chimpanzees, bonobos, and gorillas inhabit rain forests that lie on or near the equator in Africa. Chimpanzees, in particular, have a wide geographic range and are found in more than a dozen countries of western and central equatorial Africa. Bonobos, on the other hand, are found only in the lowland rain forests of the Democratic Republic of the Congo in central Africa.
Gibbons and orangutans are arboreal, meaning they live mainly in trees. The orangutan, in fact, is the largest tree-dwelling animal in the world. Sometimes adult male orangutans have to descend to the ground to travel long distances, as the smaller tree branches cannot support their weight. Chimpanzees spend time both on the trees and the ground. Chimpanzees and bonobos come down to the ground to cover larger distances. Most of their feeding otherwise takes place on the trees. Gorillas are largely terrestrial, that is, they spend most of their time on the ground.
Most apes are active during the day. At night they lodge in trees and all except gibbons build sleeping nests for the purpose.
Physical characteristics
Apes share many characteristics, yet each species is quite distinctive in appearance. For instance, all apes have hair, but the color and volume varies from species to species. Gibbons range from tan or silvery to brown or black. Orangutans have a long, reddish-brown coat, or pelage, and are sometimes also called the red ape. Chimpanzees sport a coat of brown or black hair. Gorillas have black skin and hair. The adult male gorilla has a prominent crest on top of the skull and a “saddle” of gray or silver hairs on the lower part of the back. Hence mature males are given the name, silverback.
Gorillas, chimpanzees, and orangutans have short, thickset bodies, long arms, and short legs. Bonobos closely resemble chimpanzees, but have longer arms and a more slender body. Gibbons have remarkably long arms though they are the smallest among apes.
Gorillas are the largest apes. They may attain a height of about 5 12 feet (170 centimeters) and a weight of 300–600 pounds (135–275 kilograms) in the wild.
One feature common to all apes, and which separates them from other primates like monkeys, is that they do not have a tail. Like humans, apes have opposable thumbs and toes, which enable them to grasp and hold objects and to climb. Their fingers and toes have flat nails instead of claws.
Behavior
Movies and books have often portrayed gorillas as ferocious. Studies, however, show that they are not aggressive by nature. Gorillas live in stable family groups of 6 to 20 animals that are led by one or two adult males. The adults are protective towards the other members of the group and turn violent only when they are disturbed or when they sense danger.
Most other apes live in groups as well, though the size of their communities varies. Adult orangutans are the only solitary apes. They come together only for a brief period of courtship before mating.
Apes usually eat shoots, fruits, leaves, seeds, and grass. Gorillas live on an entirely vegetarian diet, but other apes may eat insects, birds' eggs, young birds, or rodents. Bonobos may even eat young antelopes, and chimpanzees sometimes stalk and kill young baboons and bush pigs.
Apes are intelligent creatures, particularly orangutans, gorillas, and chimpanzees. Chimpanzees in the wild use sticks as tools. For instance, they cleverly poke twigs, grass, or other objects into ant and termite nests, withdraw them, and eat the insects that cling to these tools.
Trainers and experimenters have taught both chimpanzees and gorillas to solve problems and use sign language. Orangutans in captivity also show considerable skill and are particularly clever with mechanical objects.
Reproduction and growth
Reproduction among apes is similar to humans. Most apes give birth to a single offspring, after a pregnancy of about seven to nine months. Twins are rare. Infants are generally helpless for the first few months after birth and depend entirely on the mother. They become sexually mature when they are 7 years or older, and may live up to 30 years. It has been noticed that apes generally live longer in captivity.
Under threat
The numbers of most ape species in the wild is shrinking because of hunting and destruction of their natural habitat. Many, like chimpanzees and gorillas, have been exported to zoos and research laboratories. In Africa, gorillas and chimpanzees are prized for their meat. In addition, infant apes bring a high price in the illegal pet trade. These species are considered either vulnerable or endangered.
Steps have been taken for their conservation. Several national parks have been established in countries like Rwanda in Africa and Indonesia and Thailand in southeastern Asia for the protection of gorillas, orangutans, and gibbons. In addition, the law in Indonesia and Malaysia protects the orangutan. The gorilla and bonobos are also protected, but illegal hunting of apes continues.
Scientist
06-10-2007, 10:20
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A prehistoric bird, Archaeopteryx is best described as a feathered dinosaur with wings. Archaeopteryx is considered proof that birds developed from dinosaurs, because it had the traits of both. The name Archaeopteryx means “ancient wing.”
Where and when Archaeopteryx lived
Archaeopteryx lived about 159 to 144 million years ago, during the period of the Earth's history known as the Jurassic. All known Archaeopteryx remains have been found in the Bavarian region of southern Germany. Scientists were able to classify Archaeopteryx as a bird because the fine-grained limestone in this region has perfectly preserved impressions of the animal's delicate feathers. Archaeopteryx lived in a tropical environment on islands among coral lagoons. Low, scrubby evergreens were the tallest trees that grew on the islands.
Physical features
Archaeopteryx ranged in size from that of a blue jay to that of a large chicken. It reached 2 feet (60 centimeters) in length and had a wingspan of 2 feet (60 centimeters). It developed long forearms, which were specially adapted to support feathers. Its primary wing feathers match those of modern pigeons, showing that Archaeopteryx could fly or glide. Archaeopteryx also shared several features with a group of small, meat-eating dinosaurs, however. One major similarity was the presence of well-developed teeth. Like these dinosaurs, Archaeopteryx had a long, slender and flexible neck. It had long leg and foot bones, and it had claws on its hands. Archaeopteryx had a long, bony tail, as well. The only difference was that feathers were attached along each side of its tail.
Behavior
Some scientists believe that Archaeopteryx took off by running along the ground and leaping into the air, flapping its wings forcefully. However, other experts believe that Archaeopteryx probably did not have the well-developed breast muscles used by modern birds to take off from level ground. These experts believe that Archaeopteryx most likely spent a lot of time perched in low-growing trees. It may have used its long, sharp claws to haul itself up the trunks of the trees. The animal could then simply launch itself from atop the low branches and glide out on short flights. When it was not in the trees it is possible that Archaeopteryx swam and fished in the lagoons surrounding the islands on which it lived. It may have wandered along the beach, searching for crabs, washed-up fish, worms, and insects. Archaeopteryx, like both dinosaurs and modern birds, reproduced by laying eggs.
A prehistoric bird, Archaeopteryx is best described as a feathered dinosaur with wings. Archaeopteryx is considered proof that birds developed from dinosaurs, because it had the traits of both. The name Archaeopteryx means “ancient wing.”
Where and when Archaeopteryx lived
Archaeopteryx lived about 159 to 144 million years ago, during the period of the Earth's history known as the Jurassic. All known Archaeopteryx remains have been found in the Bavarian region of southern Germany. Scientists were able to classify Archaeopteryx as a bird because the fine-grained limestone in this region has perfectly preserved impressions of the animal's delicate feathers. Archaeopteryx lived in a tropical environment on islands among coral lagoons. Low, scrubby evergreens were the tallest trees that grew on the islands.
Physical features
Archaeopteryx ranged in size from that of a blue jay to that of a large chicken. It reached 2 feet (60 centimeters) in length and had a wingspan of 2 feet (60 centimeters). It developed long forearms, which were specially adapted to support feathers. Its primary wing feathers match those of modern pigeons, showing that Archaeopteryx could fly or glide. Archaeopteryx also shared several features with a group of small, meat-eating dinosaurs, however. One major similarity was the presence of well-developed teeth. Like these dinosaurs, Archaeopteryx had a long, slender and flexible neck. It had long leg and foot bones, and it had claws on its hands. Archaeopteryx had a long, bony tail, as well. The only difference was that feathers were attached along each side of its tail.
Behavior
Some scientists believe that Archaeopteryx took off by running along the ground and leaping into the air, flapping its wings forcefully. However, other experts believe that Archaeopteryx probably did not have the well-developed breast muscles used by modern birds to take off from level ground. These experts believe that Archaeopteryx most likely spent a lot of time perched in low-growing trees. It may have used its long, sharp claws to haul itself up the trunks of the trees. The animal could then simply launch itself from atop the low branches and glide out on short flights. When it was not in the trees it is possible that Archaeopteryx swam and fished in the lagoons surrounding the islands on which it lived. It may have wandered along the beach, searching for crabs, washed-up fish, worms, and insects. Archaeopteryx, like both dinosaurs and modern birds, reproduced by laying eggs.
Scientist
06-10-2007, 10:23
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Armadillos are small, piglike mammals related to sloths and anteaters. They have a bony armor that protects them from enemies and other dangers. The word armadillo is Spanish for “little armored one.”
Where armadillos live
Armadillos belong to the scientific family Dasypodidae, which contains 20 species. They are found mainly in or near tropical regions of Central and South America. One species can be found in the central United States. Most species inhabit open areas, but some live in forests.
Physical characteristics
Armadillos are stout, short-legged animals with strong, curved claws. They are usually brownish black, marked with yellow above and yellowish white underneath. Their armor is made up of solid plates and flexible bands. It covers most of the body, including the head and usually the tail. The three-, six-, and nine-banded armadillos are named for the number of movable bands in their armor. Species range in length from about 6 inches (15 centimeters) to 5 feet (1.5 meters).
The coat of armadillos varies among the species. Some armadillos, such as the nine-banded species, have very little hair. The pink fairy armadillo, however, has a fairly dense coat of soft, white hair on its underparts and sides.
Behavior
Armadillos live alone, in pairs, or in small groups. They are usually active at night. They live in burrows and can dig very quickly. Armadillos feed mainly on termites and other insects, worms, roots, and small animals. They can run surprisingly fast on their short legs and are good swimmers. Before entering the water they swallow air to help keep afloat.
Armadillos are timid animals. When threatened, they retreat to their burrows when possible. If caught in the open, they draw in their feet so their armor touches the ground. They may also run away or claw at the attacker. The three-banded armadillos are able to roll up into a ball to protect their underparts.
Female armadillos of some species bear one to 12 identical young. All develop from a single egg, or ovum, and are the same ***.
Armadillos are small, piglike mammals related to sloths and anteaters. They have a bony armor that protects them from enemies and other dangers. The word armadillo is Spanish for “little armored one.”
Where armadillos live
Armadillos belong to the scientific family Dasypodidae, which contains 20 species. They are found mainly in or near tropical regions of Central and South America. One species can be found in the central United States. Most species inhabit open areas, but some live in forests.
Physical characteristics
Armadillos are stout, short-legged animals with strong, curved claws. They are usually brownish black, marked with yellow above and yellowish white underneath. Their armor is made up of solid plates and flexible bands. It covers most of the body, including the head and usually the tail. The three-, six-, and nine-banded armadillos are named for the number of movable bands in their armor. Species range in length from about 6 inches (15 centimeters) to 5 feet (1.5 meters).
The coat of armadillos varies among the species. Some armadillos, such as the nine-banded species, have very little hair. The pink fairy armadillo, however, has a fairly dense coat of soft, white hair on its underparts and sides.
Behavior
Armadillos live alone, in pairs, or in small groups. They are usually active at night. They live in burrows and can dig very quickly. Armadillos feed mainly on termites and other insects, worms, roots, and small animals. They can run surprisingly fast on their short legs and are good swimmers. Before entering the water they swallow air to help keep afloat.
Armadillos are timid animals. When threatened, they retreat to their burrows when possible. If caught in the open, they draw in their feet so their armor touches the ground. They may also run away or claw at the attacker. The three-banded armadillos are able to roll up into a ball to protect their underparts.
Female armadillos of some species bear one to 12 identical young. All develop from a single egg, or ovum, and are the same ***.
Scientist
06-10-2007, 10:26
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Baboons are large monkeys that move around both on the ground and in trees. They are very smart, noisy, and often ferocious.
Where baboons live
Baboons are found in Africa south of the Sahara and in Arabia. They are able to live in a variety of places, including open woodlands, grasslands, and rocky hills. They spend most of their time on the ground, but they sleep in high places, including in trees and on cliffs.
Physical features
The head and face of a baboon are similar to those of a dog. Baboons have large cheek pouches and a long muzzle, or snout. Their front teeth are huge, and their limbs are powerful. They walk on all four legs.
Depending on the species, or type, a baboon can weigh from 30 to 88 pounds (14 to 40 kilograms) and measure from 20 to 45 inches (51 to 114 centimeters) long, not including the tail. A baboon's tail is usually about 16 to 28 inches (41 to 71 centimeters) long. Adult males are about twice the size of adult females.
Baboons can be different colors, including ash gray, reddish brown, olive brown, and yellow green. No matter what the color is, however, a baboon's fur is always rough. Adult males often have capes of long hair over their shoulders. The underparts, hands, feet, face, and buttocks of a baboon do not have fur.
Behavior
Baboons eat many different plants and animals, including grass, fruit, roots, birds, and small mammals such as rodents, hares, and gazelle fawns. Their diet varies from region to region depending on what food is available. Baboons can be very destructive to farmland.
Baboons live and travel in large groups called troops. Each troop is a very close society. Troops are led and guarded by one or more males. Baboons communicate with each other and have a number of calls that mean different things. For example, they announce alarm with a doglike bark. Baboons are thought to be very smart creatures that can be trained.
Life cycle
Male and female baboons do not stay together after mating. Instead they mate with other members of the opposite ***. Female baboons typically give birth to a single young. Although females remain with their mothers as they grow older, males leave at about age 7 to join other troops. Baboons may live 20 to 30 years in the wild and considerably longer in zoos.
Baboons are large monkeys that move around both on the ground and in trees. They are very smart, noisy, and often ferocious.
Where baboons live
Baboons are found in Africa south of the Sahara and in Arabia. They are able to live in a variety of places, including open woodlands, grasslands, and rocky hills. They spend most of their time on the ground, but they sleep in high places, including in trees and on cliffs.
Physical features
The head and face of a baboon are similar to those of a dog. Baboons have large cheek pouches and a long muzzle, or snout. Their front teeth are huge, and their limbs are powerful. They walk on all four legs.
Depending on the species, or type, a baboon can weigh from 30 to 88 pounds (14 to 40 kilograms) and measure from 20 to 45 inches (51 to 114 centimeters) long, not including the tail. A baboon's tail is usually about 16 to 28 inches (41 to 71 centimeters) long. Adult males are about twice the size of adult females.
Baboons can be different colors, including ash gray, reddish brown, olive brown, and yellow green. No matter what the color is, however, a baboon's fur is always rough. Adult males often have capes of long hair over their shoulders. The underparts, hands, feet, face, and buttocks of a baboon do not have fur.
Behavior
Baboons eat many different plants and animals, including grass, fruit, roots, birds, and small mammals such as rodents, hares, and gazelle fawns. Their diet varies from region to region depending on what food is available. Baboons can be very destructive to farmland.
Baboons live and travel in large groups called troops. Each troop is a very close society. Troops are led and guarded by one or more males. Baboons communicate with each other and have a number of calls that mean different things. For example, they announce alarm with a doglike bark. Baboons are thought to be very smart creatures that can be trained.
Life cycle
Male and female baboons do not stay together after mating. Instead they mate with other members of the opposite ***. Female baboons typically give birth to a single young. Although females remain with their mothers as they grow older, males leave at about age 7 to join other troops. Baboons may live 20 to 30 years in the wild and considerably longer in zoos.
Scientist
06-10-2007, 10:30
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Badgers are mammals known for their powerful digging. The eight species, or types, of badgers differ in color and size, but all belong to the weasel family. Another member of the weasel family, the ratel of Africa and Asia, is called a honey badger, but scientists do not consider it to be a true badger.
Where badgers live
Badgers live in grasslands and forests. They are found on all northern continents and on many islands. The American badger lives in the western part of North America, from Canada to Mexico. Its territory centers on the Great Plains. The Eurasian badger can be found across the entire length of Europe and Asia, from Great Britain to Japan. Other badgers, including the hog badger, three kinds of ferret badgers, and two kinds of stink badgers, live in Southeast Asia and the large islands nearby.
Physical features
Badgers are mostly medium-sized animals, heavily built with short legs. The American badger sometimes appears to be wider than it is tall. It is about 9 inches (23 centimeters) high and 17 to 30 inches (43 to 76 centimeters) in length, with a weight of 8 to 25 pounds (4 to 11 kilograms). Most of its coat is gray, but it has a blackish face and feet and a white stripe from its nose to its back. The Eurasian badger is the largest of the badgers. It weighs between 22 and 50 pounds (10 and 23 kilograms). It is grayish with large black-and-white stripes on its face. Other badgers also have fur patterns of black and white.
Behavior
Badgers have strong forefeet, and their claws are built for digging. The American badger is a faster digger than a human with a shovel. Badgers dig to get at the burrowing rodents and other underground creatures that they eat. Badgers sometimes eat birds and plants as well. They feed mainly at night.
Badgers also use their digging skills to make burrows for themselves. American badgers live alone in their burrows, but Eurasian badgers live in groups with extensive networks of homes and escape routes. Badgers do not hibernate through cold winters, but they do stay underground for long periods.
Badgers are strong for their size and can fight savagely when threatened. All badgers have scent glands near the tail, but the stink badgers are especially known for shooting a foul-smelling liquid at their enemies.
Reproduction
For most badgers, the time between mating and the birth of the young is quite long. In American badgers the period of pregnancy may be seven months or more, and in Eurasian badgers it may be almost an entire year. Litters consist of one to seven young. The young are raised in the burrow until they are several months old.
Badgers and humans
Badgers help humans by eating many rodent pests, which may carry disease or damage crops. But some people consider badgers to be pests, too, because their burrows can be a hazard to cattle and horses. Such large animals have been known to break legs by stepping into a badger hole.
In the past, badgers were a valuable source of fur. Badger fur has been used as a trim on many types of Native American clothing.
Badgers are mammals known for their powerful digging. The eight species, or types, of badgers differ in color and size, but all belong to the weasel family. Another member of the weasel family, the ratel of Africa and Asia, is called a honey badger, but scientists do not consider it to be a true badger.
Where badgers live
Badgers live in grasslands and forests. They are found on all northern continents and on many islands. The American badger lives in the western part of North America, from Canada to Mexico. Its territory centers on the Great Plains. The Eurasian badger can be found across the entire length of Europe and Asia, from Great Britain to Japan. Other badgers, including the hog badger, three kinds of ferret badgers, and two kinds of stink badgers, live in Southeast Asia and the large islands nearby.
Physical features
Badgers are mostly medium-sized animals, heavily built with short legs. The American badger sometimes appears to be wider than it is tall. It is about 9 inches (23 centimeters) high and 17 to 30 inches (43 to 76 centimeters) in length, with a weight of 8 to 25 pounds (4 to 11 kilograms). Most of its coat is gray, but it has a blackish face and feet and a white stripe from its nose to its back. The Eurasian badger is the largest of the badgers. It weighs between 22 and 50 pounds (10 and 23 kilograms). It is grayish with large black-and-white stripes on its face. Other badgers also have fur patterns of black and white.
Behavior
Badgers have strong forefeet, and their claws are built for digging. The American badger is a faster digger than a human with a shovel. Badgers dig to get at the burrowing rodents and other underground creatures that they eat. Badgers sometimes eat birds and plants as well. They feed mainly at night.
Badgers also use their digging skills to make burrows for themselves. American badgers live alone in their burrows, but Eurasian badgers live in groups with extensive networks of homes and escape routes. Badgers do not hibernate through cold winters, but they do stay underground for long periods.
Badgers are strong for their size and can fight savagely when threatened. All badgers have scent glands near the tail, but the stink badgers are especially known for shooting a foul-smelling liquid at their enemies.
Reproduction
For most badgers, the time between mating and the birth of the young is quite long. In American badgers the period of pregnancy may be seven months or more, and in Eurasian badgers it may be almost an entire year. Litters consist of one to seven young. The young are raised in the burrow until they are several months old.
Badgers and humans
Badgers help humans by eating many rodent pests, which may carry disease or damage crops. But some people consider badgers to be pests, too, because their burrows can be a hazard to cattle and horses. Such large animals have been known to break legs by stepping into a badger hole.
In the past, badgers were a valuable source of fur. Badger fur has been used as a trim on many types of Native American clothing.
Scientist
07-10-2007, 08:11
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Bold and curious, barracudas are among the most ferocious fish in tropical waters. The species known as the great barracuda has even been known to attack humans. Barracudas live in the warmer parts of the Atlantic and Pacific oceans, including in the Caribbean Sea.
Physical features
A barracuda has a fierce appearance. Its long mouth has a jutting lower jaw and large, knifelike teeth. Its torpedo-shaped body, built for speed, has small scales and two well-separated fins on the back. Barracudas vary in size, but they average 3 to 4 feet (1 meter) in length. The largest type is the great barracuda, which can reach a length of 8 feet (2 meters).
Behavior
Barracudas are primarily fish eaters. They prey on smaller fish like mullets, anchovies, and grunts. Sometimes they even bite through fishermen's nets to get at the fish inside. Barracudas travel far in search of food. When they find a school of fish, they circle around it until the fish huddle together in fear. Then the barracudas dive into the group while biting and slashing with their teeth. Barracudas will strike at most moving objects, including swimmers.
Bold and curious, barracudas are among the most ferocious fish in tropical waters. The species known as the great barracuda has even been known to attack humans. Barracudas live in the warmer parts of the Atlantic and Pacific oceans, including in the Caribbean Sea.
Physical features
A barracuda has a fierce appearance. Its long mouth has a jutting lower jaw and large, knifelike teeth. Its torpedo-shaped body, built for speed, has small scales and two well-separated fins on the back. Barracudas vary in size, but they average 3 to 4 feet (1 meter) in length. The largest type is the great barracuda, which can reach a length of 8 feet (2 meters).
Behavior
Barracudas are primarily fish eaters. They prey on smaller fish like mullets, anchovies, and grunts. Sometimes they even bite through fishermen's nets to get at the fish inside. Barracudas travel far in search of food. When they find a school of fish, they circle around it until the fish huddle together in fear. Then the barracudas dive into the group while biting and slashing with their teeth. Barracudas will strike at most moving objects, including swimmers.
Scientist
07-10-2007, 08:25
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The only mammal that flies is the bat. Because of this trait, bats are often mistaken for birds. Bat wings differ from bird wings, however, in that they are covered with skin, not feathers.
Where bats live
About 900 kinds of bats are known, more than any other kind of mammal except rodents. They are found worldwide but are particularly abundant in the tropics. The United States is known to have 40 species of bats. In North America the little brown bat is the most common type.
Bats generally prefer dark places such as caves, hollow trees, or attics. Some bats, however, rest outdoors on trees or rocks. Usually bats are found in groups, or colonies, ranging from a few dozen to hundreds of thousands of individuals.
Physical characteristics
Bats vary greatly in size. The largest of the bats known as flying foxes has a wingspread as wide as 5 feet (1.5 meters). The wingspread of the tiny Kitti's hognose bat, however, is only about 6 inches (15 centimeters).
Bats also display variety in color, fur texture, and facial appearance. The muzzle often resembles that of a rodent or fox. The ears point forward and are usually very large. Bats have fur in shades of gray, tan, brown, or black on the back and in lighter shades on the sides.
Bats have long arms and hands, with especially long fingers. The fingers are joined by a thin membrane that extends from the arms to the tiny legs. This membrane serves as the bat's wings.
Feeding habits
Nearly all bats rest during the day and search for food at night. Most bats eat insects. A brown bat may eat half its weight in insects in one night. In some parts of the southern United States, huge roosts, or shelters, have been erected for bats because the bats are so useful in controlling the insect population.
Some bats have specialized diets. Several species are carnivorous, or meat eating. They feed on a variety of prey, including birds, smaller bats, rodents, and fish. Other bats feed on fruit, pollen, and nectar. The famous vampire bats of South and Central America feed on the blood of mammals and large birds. These bats sometimes serve as carriers of rabies.
Life cycle
Female bats usually bear one young at a time. The pregnancy can last from six or seven weeks to five or six months, depending on the species. Infants are born nude or with light fur. They nurse for five or six weeks or for as long as five months.
Bats have a long life span for animals of their size. Some bats are known to have lived more than 20 years.
Flight and navigation
Bats are well adapted for flying. Most bats cannot walk or run. A bat's legs and feet are only strong enough to hold on when it hangs upside down from a perch, which is how bats rest or sleep. To start flying, a bat drops from its perch. If it is on the ground it usually crawls to some height, using its wing hooks and weak legs, until it can drop into the air. It can, however, take off from a position on the ground if necessary.
Bats can chase insects through thick forests on the darkest night without striking a branch or twig. While flying, most bats send out a continuous cry, so high-pitched that people cannot hear it. These sounds are reflected by obstacles in the bat's path and echo back to the bat's sensitive ears. The animal instantly responds to the signals and avoids the obstacles.
The only mammal that flies is the bat. Because of this trait, bats are often mistaken for birds. Bat wings differ from bird wings, however, in that they are covered with skin, not feathers.
Where bats live
About 900 kinds of bats are known, more than any other kind of mammal except rodents. They are found worldwide but are particularly abundant in the tropics. The United States is known to have 40 species of bats. In North America the little brown bat is the most common type.
Bats generally prefer dark places such as caves, hollow trees, or attics. Some bats, however, rest outdoors on trees or rocks. Usually bats are found in groups, or colonies, ranging from a few dozen to hundreds of thousands of individuals.
Physical characteristics
Bats vary greatly in size. The largest of the bats known as flying foxes has a wingspread as wide as 5 feet (1.5 meters). The wingspread of the tiny Kitti's hognose bat, however, is only about 6 inches (15 centimeters).
Bats also display variety in color, fur texture, and facial appearance. The muzzle often resembles that of a rodent or fox. The ears point forward and are usually very large. Bats have fur in shades of gray, tan, brown, or black on the back and in lighter shades on the sides.
Bats have long arms and hands, with especially long fingers. The fingers are joined by a thin membrane that extends from the arms to the tiny legs. This membrane serves as the bat's wings.
Feeding habits
Nearly all bats rest during the day and search for food at night. Most bats eat insects. A brown bat may eat half its weight in insects in one night. In some parts of the southern United States, huge roosts, or shelters, have been erected for bats because the bats are so useful in controlling the insect population.
Some bats have specialized diets. Several species are carnivorous, or meat eating. They feed on a variety of prey, including birds, smaller bats, rodents, and fish. Other bats feed on fruit, pollen, and nectar. The famous vampire bats of South and Central America feed on the blood of mammals and large birds. These bats sometimes serve as carriers of rabies.
Life cycle
Female bats usually bear one young at a time. The pregnancy can last from six or seven weeks to five or six months, depending on the species. Infants are born nude or with light fur. They nurse for five or six weeks or for as long as five months.
Bats have a long life span for animals of their size. Some bats are known to have lived more than 20 years.
Flight and navigation
Bats are well adapted for flying. Most bats cannot walk or run. A bat's legs and feet are only strong enough to hold on when it hangs upside down from a perch, which is how bats rest or sleep. To start flying, a bat drops from its perch. If it is on the ground it usually crawls to some height, using its wing hooks and weak legs, until it can drop into the air. It can, however, take off from a position on the ground if necessary.
Bats can chase insects through thick forests on the darkest night without striking a branch or twig. While flying, most bats send out a continuous cry, so high-pitched that people cannot hear it. These sounds are reflected by obstacles in the bat's path and echo back to the bat's sensitive ears. The animal instantly responds to the signals and avoids the obstacles.
Scientist
07-10-2007, 08:27
Bears loom large in legends and folk tales. Stuffed bears and fictional bears such as A.A. Milne's Winnie the Pooh continue to delight children. However, bears also call to mind images of fierce creatures. Despite their reputation for ferocity, most bears are mild tempered animals. They become violent only when their food supplies or their young are threatened.
Where bears live
Bears are found in North America, Europe, and Asia. One species lives in South America. However, there are no bears in tropical Africa, a region otherwise well stocked with large mammals.
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The polar bear lives mostly in the Arctic north, where its white fur blends in with snow and ice. Polar bears are often seen on drifting masses of floating sea ice called floes. Brown bears, once widespread in Europe and Asia, are now rare. The grizzly bear, a brown bear of northern and western North America, has been killed off in many areas. The Kodiak bear, an Alaskan island bear closely related to the grizzly, is the world's largest living flesh-eating land mammal.
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The American black bear is smaller than the brown bears. It still ranges widely in the forests of the United States and Canada. There is also an Asian, or Himalayan black bear. Most bears live in cold or temperate climates, but the sloth bear is a creature of the tropics. It lives in India and Sri Lanka. The sun bear, or Malayan sun bear, lives in the forests of Southeast Asia. The spectacled bear, which gets its name from the light-colored rings around its eyes, is the only bear of the Southern Hemisphere. It is found in the Andes Mountains of Chile, Bolivia, Ecuador, and Peru.
Physical characteristics
Bears vary in size according to their species. Generally, their height ranges from 3 to 10 feet (1 to 3 meters). The sun bear is the smallest, at 60 to 143 pounds (27 to 65 kilograms). The Alaskan brown bear known as the Kodiak bear is the largest. It weighs up to 1,720 pounds (780 kilograms). Most bears climb trees with ease and swim well. The polar bear has furry soles to its feet that help it run safely over smooth ice. It also has a membrane between its toes for swimming. Bears have poor eyesight, and most have only moderate hearing. Their sense of smell, however, is extremely keen.
Food habits
Biologists classify bears as carnivores, or meat eaters. The polar bear lives on a diet of walrus, seals, and fish. Other bears eat large quantities of vegetable matter, especially roots, seeds, nuts, and berries, as well as meat. Because they eat both meat and vegetables, bears are sometimes referred to as omnivores, or eaters of everything. Bears will even feed on the carcasses of dead animals where they find them. They also sometimes rummage through garbage dumps, making nuisances of themselves.
Behavior
Bears are solitary creatures that avoid each other except in the mating season. Female bears give birth to one to four cubs at a time, usually in winter. Newborn cubs are small, hairless, and helpless creatures unable to open their eyes for about a week. A newborn grizzly bear weighs as little as 1 pound (0.45 kilogram). Cubs drink their mother's milk for about two months and stay with her until the next breeding period begins, which is usually about a year and a half after their birth. Bears begin to breed at 2 to 6 years of age. The male bear plays no role in raising the cubs. Most bears live from 15 to 30 years in the wild. Captive bears have lived much longer.
During the winter most bears in the wild become inactive for a period of two to six months. In the autumn season the bears eat a great deal and seek out comfortable dens where they can sleep for a long time. This process is similar to hibernation, in which animals sleep through the winter. However, bears are not true hibernators. Their heartbeat rate, body temperature, breathing rate, and blood pressure do not drop significantly lower than normal. And on mild days in midwinter, a bear may come out of its den.
Survival
Tens of thousands of years ago Europeans of the Stone Age hunted the cave bear, a very large species that is now extinct. Bears are still hunted as trophies, or for various assets such as their meat, fur, teeth, and fat. Because of extensive hunting and destruction of their habitat by humans, the brown bear has been almost eliminated from many parts of Europe. In North America the grizzly bear had a reputation for ferocity and was a favorite prey of hunters. During the 19th century grizzlies almost died out in the United States.
Bears are now protected in national parks of many countries, and hunting is carefully regulated. In 1973 conservationists agreed that urgent measures were needed to save the polar bear. As a result, all countries bordering the Arctic Circle now protect the animal. Polar bears cannot be hunted, except by local people using traditional weapons. In the mid-1980s conservationists established programs to protect the grizzly bear population in the western United States.
Where bears live
Bears are found in North America, Europe, and Asia. One species lives in South America. However, there are no bears in tropical Africa, a region otherwise well stocked with large mammals.
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The polar bear lives mostly in the Arctic north, where its white fur blends in with snow and ice. Polar bears are often seen on drifting masses of floating sea ice called floes. Brown bears, once widespread in Europe and Asia, are now rare. The grizzly bear, a brown bear of northern and western North America, has been killed off in many areas. The Kodiak bear, an Alaskan island bear closely related to the grizzly, is the world's largest living flesh-eating land mammal.
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The American black bear is smaller than the brown bears. It still ranges widely in the forests of the United States and Canada. There is also an Asian, or Himalayan black bear. Most bears live in cold or temperate climates, but the sloth bear is a creature of the tropics. It lives in India and Sri Lanka. The sun bear, or Malayan sun bear, lives in the forests of Southeast Asia. The spectacled bear, which gets its name from the light-colored rings around its eyes, is the only bear of the Southern Hemisphere. It is found in the Andes Mountains of Chile, Bolivia, Ecuador, and Peru.
Physical characteristics
Bears vary in size according to their species. Generally, their height ranges from 3 to 10 feet (1 to 3 meters). The sun bear is the smallest, at 60 to 143 pounds (27 to 65 kilograms). The Alaskan brown bear known as the Kodiak bear is the largest. It weighs up to 1,720 pounds (780 kilograms). Most bears climb trees with ease and swim well. The polar bear has furry soles to its feet that help it run safely over smooth ice. It also has a membrane between its toes for swimming. Bears have poor eyesight, and most have only moderate hearing. Their sense of smell, however, is extremely keen.
Food habits
Biologists classify bears as carnivores, or meat eaters. The polar bear lives on a diet of walrus, seals, and fish. Other bears eat large quantities of vegetable matter, especially roots, seeds, nuts, and berries, as well as meat. Because they eat both meat and vegetables, bears are sometimes referred to as omnivores, or eaters of everything. Bears will even feed on the carcasses of dead animals where they find them. They also sometimes rummage through garbage dumps, making nuisances of themselves.
Behavior
Bears are solitary creatures that avoid each other except in the mating season. Female bears give birth to one to four cubs at a time, usually in winter. Newborn cubs are small, hairless, and helpless creatures unable to open their eyes for about a week. A newborn grizzly bear weighs as little as 1 pound (0.45 kilogram). Cubs drink their mother's milk for about two months and stay with her until the next breeding period begins, which is usually about a year and a half after their birth. Bears begin to breed at 2 to 6 years of age. The male bear plays no role in raising the cubs. Most bears live from 15 to 30 years in the wild. Captive bears have lived much longer.
During the winter most bears in the wild become inactive for a period of two to six months. In the autumn season the bears eat a great deal and seek out comfortable dens where they can sleep for a long time. This process is similar to hibernation, in which animals sleep through the winter. However, bears are not true hibernators. Their heartbeat rate, body temperature, breathing rate, and blood pressure do not drop significantly lower than normal. And on mild days in midwinter, a bear may come out of its den.
Survival
Tens of thousands of years ago Europeans of the Stone Age hunted the cave bear, a very large species that is now extinct. Bears are still hunted as trophies, or for various assets such as their meat, fur, teeth, and fat. Because of extensive hunting and destruction of their habitat by humans, the brown bear has been almost eliminated from many parts of Europe. In North America the grizzly bear had a reputation for ferocity and was a favorite prey of hunters. During the 19th century grizzlies almost died out in the United States.
Bears are now protected in national parks of many countries, and hunting is carefully regulated. In 1973 conservationists agreed that urgent measures were needed to save the polar bear. As a result, all countries bordering the Arctic Circle now protect the animal. Polar bears cannot be hunted, except by local people using traditional weapons. In the mid-1980s conservationists established programs to protect the grizzly bear population in the western United States.
Scientist
07-10-2007, 08:56
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The large rodents called beavers are known for using their teeth and paws to build lodges, storehouses, dams, and canals. Beavers are amphibious, which means they are able to live both in water and on land.
Where beavers live
Beavers are native to North America, Europe, and Asia. Today they are found mostly in the northern wooded regions of North America and Europe. Beavers live most of their lives in or near water. They settle along banks of streams, rivers, and lakes bordered by woodland.
Physical features
Beavers are the largest rodents in North America and the second largest in the world after the capybara of South America. An adult beaver may grow to be about 4 feet (1.3 meters) long, including its tail. It may weigh more than 60 pounds (27 kilograms).
A beaver's thick body is covered with a coat of long, reddish-brown outer hairs and soft, dense, brown underfur. This warm, waterproof coat allows the beaver to swim in icy water in the wintertime. Most of a beaver's features—the fur, toes, tail, ears, nose, and lips—allow the animal to live in the water as well as on land. For example, beavers have ears and a nose that are equipped with valves that close when the animal swims underwater. In addition, a beaver's lips close behind its big front teeth so the animal can cut wood and branches underwater. Because of these features, a beaver may remain underwater for up to 15 minutes.
A beaver's front feet are small and look much like a human hand. Beavers use their hands to pick up and carry objects. The tail is scaly, flat, and shaped like a paddle. A beaver uses its tail to warn other beavers of danger by slapping it on the water's surface and making a loud noise.
Behavior
Beavers are nocturnal, which means that they do most of their building and food gathering at night. Beavers eat fresh green bark and the buds, leaves, and twigs of certain trees. In the summer they also eat water plants, berries, swampwood, and fruit.
Beavers are social animals that live and work together. Large groups of beavers build dams in narrow, shallow parts of streams. The beavers begin by gnawing down a number of young trees. They drag these trees to the dam site and bury them in mud. Into this foundation the beavers fit and pile more young trees, adding mud and stones until a strong barrier is completed. Sometimes the beavers build canals to help move logs that are too heavy to drag overland.
The artificial pond created by the dam is where the beavers make their storehouses and permanent homes, or lodges. A lodge is usually the work of a pair of beavers. It is made up of a platform of carefully interlaced branches held together by clay and dead leaves. A dome-shaped roof covers the platform. The lodge may be more than 5 feet (1.5 meters) high. Entrances to the lodge often open underwater. This allows the animals to pass in and out below the winter ice. Another entrance is used for bringing in wood for food. A lodge may be home to as many as eight animals, including an adult pair and two sets of offspring.
Life cycle
Beavers usually mate with the same partner for life. The female is pregnant for about 105 days before giving birth to her young, which are called kits. A litter includes one to nine kits, with four being the most common size. Kits learn to swim when they are only a month old. Beavers may live as long as 19 years.
Beavers and humans
Beavers have been hunted for their fur, their tails, and their musk glands. Musk glands are scent glands at the rear of a beaver's body that produce a liquid used to make perfumes. During the 17th, 18th, and early 19th centuries, beaver skins were an important part of the world's fur trade. In fact, much of the exploration of North America was prompted by the search for beaver fur. Beginning in the 20th century, however, conservation laws were passed to protect beavers throughout the world. As a result, beavers have been saved and resettled in areas where they had once been common.
The large rodents called beavers are known for using their teeth and paws to build lodges, storehouses, dams, and canals. Beavers are amphibious, which means they are able to live both in water and on land.
Where beavers live
Beavers are native to North America, Europe, and Asia. Today they are found mostly in the northern wooded regions of North America and Europe. Beavers live most of their lives in or near water. They settle along banks of streams, rivers, and lakes bordered by woodland.
Physical features
Beavers are the largest rodents in North America and the second largest in the world after the capybara of South America. An adult beaver may grow to be about 4 feet (1.3 meters) long, including its tail. It may weigh more than 60 pounds (27 kilograms).
A beaver's thick body is covered with a coat of long, reddish-brown outer hairs and soft, dense, brown underfur. This warm, waterproof coat allows the beaver to swim in icy water in the wintertime. Most of a beaver's features—the fur, toes, tail, ears, nose, and lips—allow the animal to live in the water as well as on land. For example, beavers have ears and a nose that are equipped with valves that close when the animal swims underwater. In addition, a beaver's lips close behind its big front teeth so the animal can cut wood and branches underwater. Because of these features, a beaver may remain underwater for up to 15 minutes.
A beaver's front feet are small and look much like a human hand. Beavers use their hands to pick up and carry objects. The tail is scaly, flat, and shaped like a paddle. A beaver uses its tail to warn other beavers of danger by slapping it on the water's surface and making a loud noise.
Behavior
Beavers are nocturnal, which means that they do most of their building and food gathering at night. Beavers eat fresh green bark and the buds, leaves, and twigs of certain trees. In the summer they also eat water plants, berries, swampwood, and fruit.
Beavers are social animals that live and work together. Large groups of beavers build dams in narrow, shallow parts of streams. The beavers begin by gnawing down a number of young trees. They drag these trees to the dam site and bury them in mud. Into this foundation the beavers fit and pile more young trees, adding mud and stones until a strong barrier is completed. Sometimes the beavers build canals to help move logs that are too heavy to drag overland.
The artificial pond created by the dam is where the beavers make their storehouses and permanent homes, or lodges. A lodge is usually the work of a pair of beavers. It is made up of a platform of carefully interlaced branches held together by clay and dead leaves. A dome-shaped roof covers the platform. The lodge may be more than 5 feet (1.5 meters) high. Entrances to the lodge often open underwater. This allows the animals to pass in and out below the winter ice. Another entrance is used for bringing in wood for food. A lodge may be home to as many as eight animals, including an adult pair and two sets of offspring.
Life cycle
Beavers usually mate with the same partner for life. The female is pregnant for about 105 days before giving birth to her young, which are called kits. A litter includes one to nine kits, with four being the most common size. Kits learn to swim when they are only a month old. Beavers may live as long as 19 years.
Beavers and humans
Beavers have been hunted for their fur, their tails, and their musk glands. Musk glands are scent glands at the rear of a beaver's body that produce a liquid used to make perfumes. During the 17th, 18th, and early 19th centuries, beaver skins were an important part of the world's fur trade. In fact, much of the exploration of North America was prompted by the search for beaver fur. Beginning in the 20th century, however, conservation laws were passed to protect beavers throughout the world. As a result, beavers have been saved and resettled in areas where they had once been common.
Scientist
07-10-2007, 08:57
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For at least 4,000 years honeybees have been kept for their honey and for beeswax, a substance used to make candles, ointments, and many other products. Honeybees and bumblebees are the best-known types of bees, but there are more than 20,000 bee species in all. They live all over the world except in Antarctica. Bees are related to wasps, hornets, and ants.
Structure and form
Most bees have short, thick bodies covered with hair. Like all insects, they have six legs and three body parts: head, thorax, and abdomen. The thorax has three segments. Each segment has a pair of legs; each of the last two segments has a pair of wings attached to it.
When in flight, a bee makes a humming sound because of the rapid movement of its wings. Normally, most bees fly at about 12 12 miles (20 kilometers) per hour, but they can go much faster.
Bees can see color, pattern, and movement with the help of three eyes on top of their heads and two huge, helmetlike compound eyes. Bees see all colors that humans do except red; in addition, bees see ultraviolet, which humans cannot. On the lower part of their heads, bees have biting jaws (mandibles) and a mouth-tongue (proboscis), which they use for sucking and lapping nectar from flowers. The female bee has a device called an ovipositor located at the end of its abdomen. The female bee uses the ovipostor to lay its eggs. It also uses the ovipositor as a weapon to inflict a painful sting. Most bees can sting many times, but a honeybee worker has a tiny, hook-shaped barb that is caught inside the victim. This bee cannot fly away without tearing out its ovipositor and dying. Male bees cannot sting.
Size
The largest bees, which include some of the leafcutter and carpenter varieties, may be up to about 1 12 inches (4 centimeters) long. Bumblebees are larger than most bees—about 1 inch (2.5 centimeters) long. Honeybees range from about 12 to 1 inch (1.3 to 2.5 centimeters), depending on the species. Some of the small leafcutter bees are only 13 inch (1 centimeter) long, and sweat bees are 310 inch (0.7 centimeter) long. The tiniest species, the mosquito bees, may be only 7100 inch (0.2 centimeter) long.
Color
Most bees have black bodies, many with yellow or brown markings. Others have yellow, red, brown, and metallic green or blue bodies, some with brilliant metallic red or purple markings. Honeybees are dark brown with dark yellow stripes. Bumblebees are usually black with wide yellow or orange bands.
Behavior
Nesting
Different species of bees nest in different ways. There are three types of bees based on the way they nest: social bees, solitary bees, and parasitic bees.
Social bees are members of colonies in which they cooperate with others to build the nest and feed and protect the young. They include honeybees, bumblebees, and tropical stingless bees. Social bees are divided into three castes, or classes. Males are called drones. There are two types of females: queens and workers. Both queens and workers lay eggs, but only the queens' are fertilized with the drones' sperm and develop into females. Eggs of the workers develop into males. Queens are not hatched as queens; they become queens when they are fed royal jelly, a substance produced by the salivary glands of the workers.
Most bees are solitary bees. They care only for themselves and their immediate family. Each female makes its own nest and cares for its offspring.
Parasitic bees, or guest bees, do not feed or care for their offspring. They sneak into the nests of other bee species to lay their eggs. They then let the workers of the other nests care for their offspring.
Feeding and pollination
Bees get all of their food from flowers. The food consists of nectar and pollen. Nectar is a sweet liquid produced by the flower's glands. The bees use their long proboscises to drink the nectar. Some bees, especially the honeybee, modify and store their nectar as honey.
Flowers also produce pollen in the form of tiny grains that cling to the bees' bodies. As bees go from one blossom to another, some of the pollen is transferred to the flowers of other plants of the same species. In this way, bees help pollinate, or fertilize, the flowers. This permits the plants to produce their fruits and seeds. The bees' greatest value by far is as pollinators of plants.
For at least 4,000 years honeybees have been kept for their honey and for beeswax, a substance used to make candles, ointments, and many other products. Honeybees and bumblebees are the best-known types of bees, but there are more than 20,000 bee species in all. They live all over the world except in Antarctica. Bees are related to wasps, hornets, and ants.
Structure and form
Most bees have short, thick bodies covered with hair. Like all insects, they have six legs and three body parts: head, thorax, and abdomen. The thorax has three segments. Each segment has a pair of legs; each of the last two segments has a pair of wings attached to it.
When in flight, a bee makes a humming sound because of the rapid movement of its wings. Normally, most bees fly at about 12 12 miles (20 kilometers) per hour, but they can go much faster.
Bees can see color, pattern, and movement with the help of three eyes on top of their heads and two huge, helmetlike compound eyes. Bees see all colors that humans do except red; in addition, bees see ultraviolet, which humans cannot. On the lower part of their heads, bees have biting jaws (mandibles) and a mouth-tongue (proboscis), which they use for sucking and lapping nectar from flowers. The female bee has a device called an ovipositor located at the end of its abdomen. The female bee uses the ovipostor to lay its eggs. It also uses the ovipositor as a weapon to inflict a painful sting. Most bees can sting many times, but a honeybee worker has a tiny, hook-shaped barb that is caught inside the victim. This bee cannot fly away without tearing out its ovipositor and dying. Male bees cannot sting.
Size
The largest bees, which include some of the leafcutter and carpenter varieties, may be up to about 1 12 inches (4 centimeters) long. Bumblebees are larger than most bees—about 1 inch (2.5 centimeters) long. Honeybees range from about 12 to 1 inch (1.3 to 2.5 centimeters), depending on the species. Some of the small leafcutter bees are only 13 inch (1 centimeter) long, and sweat bees are 310 inch (0.7 centimeter) long. The tiniest species, the mosquito bees, may be only 7100 inch (0.2 centimeter) long.
Color
Most bees have black bodies, many with yellow or brown markings. Others have yellow, red, brown, and metallic green or blue bodies, some with brilliant metallic red or purple markings. Honeybees are dark brown with dark yellow stripes. Bumblebees are usually black with wide yellow or orange bands.
Behavior
Nesting
Different species of bees nest in different ways. There are three types of bees based on the way they nest: social bees, solitary bees, and parasitic bees.
Social bees are members of colonies in which they cooperate with others to build the nest and feed and protect the young. They include honeybees, bumblebees, and tropical stingless bees. Social bees are divided into three castes, or classes. Males are called drones. There are two types of females: queens and workers. Both queens and workers lay eggs, but only the queens' are fertilized with the drones' sperm and develop into females. Eggs of the workers develop into males. Queens are not hatched as queens; they become queens when they are fed royal jelly, a substance produced by the salivary glands of the workers.
Most bees are solitary bees. They care only for themselves and their immediate family. Each female makes its own nest and cares for its offspring.
Parasitic bees, or guest bees, do not feed or care for their offspring. They sneak into the nests of other bee species to lay their eggs. They then let the workers of the other nests care for their offspring.
Feeding and pollination
Bees get all of their food from flowers. The food consists of nectar and pollen. Nectar is a sweet liquid produced by the flower's glands. The bees use their long proboscises to drink the nectar. Some bees, especially the honeybee, modify and store their nectar as honey.
Flowers also produce pollen in the form of tiny grains that cling to the bees' bodies. As bees go from one blossom to another, some of the pollen is transferred to the flowers of other plants of the same species. In this way, bees help pollinate, or fertilize, the flowers. This permits the plants to produce their fruits and seeds. The bees' greatest value by far is as pollinators of plants.
Scientist
07-10-2007, 08:58
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The term beetle refers to thousands of different insects. There are so many beetles that they make up almost 20 percent of all known species of animals in the world.
Where beetles live
Beetles are found all over the world except in Antarctica. Most of the species live on the land. However, some, like the whirligig, water scavenger, and true water beetle, have adapted to live in the water.
Physical features
Like other insects, beetles have three major body segments: the head, thorax, and abdomen. A beetle's head has one pair of antennae and a pair of compound eyes. The thorax has two pairs of wings and three pairs of legs. The abdomen of a beetle has the reproductive organs.
Beetles have antennae, or feelers, to help them find food and recognize other beetles. The body is covered with a hard layer called cuticle that supports the internal organs and protects the body. Beetles have chewing jaws called mandibles.
Beetles are colorful insects ranging from brilliant orange, red, or yellow to iridescent green or blue with a metallic sheen. Some are plain black or have brownish patterns that camouflage them on wood or soil.
Beetles vary in size. Some are only about 1100 inch (0.025 centimeter) long, whereas tropical rhinoceros beetles and goliath beetles may reach lengths of 4 to 6 inches (10 to 15 centimeters). At one time, all beetles were flying insects, but many, like the common ground beetle, have given up flying and move about on their six legs.
Behavior
There are two kinds of beetles, the helpful and the harmful. The helpful kind are valuable because they prey on insect pests and useless garbage that collects in houses, hedges, tree stumps, birds' nests, and similar places. The harmful kinds are those, both adults and larvae, who destroy crops and timber and spread diseases.
Beetles stridulate, or make a high-pitched sound, by rubbing one part of the body against another. This is done by scraping the legs over very fine ridges on another part of the body. When frightened, some of them eject an unpleasant-smelling liquid from the end of their body.
Life cycle
Many beetles produce light and sound to either attract a mate or frighten an enemy. A male beetle, such as a firefly, flashes its light to say that it is ready to mate, and a female returns the signal.
The females lay fertilized eggs. When active larvae called grubs hatch from the eggs, they spend all their time eating. Most grubs eat leaves, flowers, stems, roots, and even the wood of trees. They shed their skin as they grow until they become pupae, when they are soft, pale and inactive. After this stage they emerge as fully grown beetles. The life span of a beetle ranges from a few months in some species to more than four years in others.
The term beetle refers to thousands of different insects. There are so many beetles that they make up almost 20 percent of all known species of animals in the world.
Where beetles live
Beetles are found all over the world except in Antarctica. Most of the species live on the land. However, some, like the whirligig, water scavenger, and true water beetle, have adapted to live in the water.
Physical features
Like other insects, beetles have three major body segments: the head, thorax, and abdomen. A beetle's head has one pair of antennae and a pair of compound eyes. The thorax has two pairs of wings and three pairs of legs. The abdomen of a beetle has the reproductive organs.
Beetles have antennae, or feelers, to help them find food and recognize other beetles. The body is covered with a hard layer called cuticle that supports the internal organs and protects the body. Beetles have chewing jaws called mandibles.
Beetles are colorful insects ranging from brilliant orange, red, or yellow to iridescent green or blue with a metallic sheen. Some are plain black or have brownish patterns that camouflage them on wood or soil.
Beetles vary in size. Some are only about 1100 inch (0.025 centimeter) long, whereas tropical rhinoceros beetles and goliath beetles may reach lengths of 4 to 6 inches (10 to 15 centimeters). At one time, all beetles were flying insects, but many, like the common ground beetle, have given up flying and move about on their six legs.
Behavior
There are two kinds of beetles, the helpful and the harmful. The helpful kind are valuable because they prey on insect pests and useless garbage that collects in houses, hedges, tree stumps, birds' nests, and similar places. The harmful kinds are those, both adults and larvae, who destroy crops and timber and spread diseases.
Beetles stridulate, or make a high-pitched sound, by rubbing one part of the body against another. This is done by scraping the legs over very fine ridges on another part of the body. When frightened, some of them eject an unpleasant-smelling liquid from the end of their body.
Life cycle
Many beetles produce light and sound to either attract a mate or frighten an enemy. A male beetle, such as a firefly, flashes its light to say that it is ready to mate, and a female returns the signal.
The females lay fertilized eggs. When active larvae called grubs hatch from the eggs, they spend all their time eating. Most grubs eat leaves, flowers, stems, roots, and even the wood of trees. They shed their skin as they grow until they become pupae, when they are soft, pale and inactive. After this stage they emerge as fully grown beetles. The life span of a beetle ranges from a few months in some species to more than four years in others.
Scientist
07-10-2007, 08:59
From pigeons in big cities to penguins in the remote icy land of Antarctica, all birds have similar characteristics. They all have wings, though they cannot all fly. All birds also have feathers. In fact, that is the one characteristic that makes them unique since birds are the only animals that do have feathers.
Where birds live
Birds are found almost everywhere on Earth, from the Antarctic ice caps to tropical forests. There are more than 9,000 known species of birds.
Many birds migrate long distances between winter and summer homes in search of a constant food supply. For example, after nesting and raising their young, many European birds travel to Africa for the winter.
Physical features
Flight
Birds are able to fly because of their body structure and feathers. A flying bird's body is slender and tapers like a jet airplane. However, not all birds can fly. Penguins spend their time in the water and ostriches have undeveloped wings. Because of this, they must walk or run everywhere. Most birds alternate some walking and swimming with their flying.
Feathers
A bird's feathers protect it from rain, cold, and heat. Water slides off a bird's feathers without soaking through. Birds fluff out their feathers on cold days. These fluffed feathers hold a layer of warm air next to their skin. In hot weather birds flatten their feathers close to their body. This keeps their skin cool by preventing hot air from reaching it. The entire covering of feathers on a bird is called plumage. A bird's feathers wear out and are replaced in a process called molting. All birds molt at least once a year, usually in the summer or early fall. Birds also preen their feathers. Birds preen by using their bill to clean, rearrange, and apply oils to their feathers.
Coloring
In many species of birds the male is more brightly colored than the female. The dull color of the females helps them to remain hidden in their nest. In some cases, the brightly colored male perches a short distance away from the nest. In this way, the male bird draws the attention of enemies to himself and away from the eggs and young.
Metabolism
Like humans, birds are warm-blooded. This means that they have a constant body temperature that is not affected by the temperature of their surroundings. Their hearts beat faster than human hearts, however, and birds breathe more rapidly than humans. Because of this, birds have a high metabolism, meaning that they use up energy very quickly. Therefore, some small birds must eat almost constantly while they are awake.
Senses
Birds have very sharp eyesight. An American kestrel hovering 100 feet (30 meters) above a field can spot a grasshopper and drop directly on it. A thin transparent membrane extends across a bird's eyeball. This membrane keeps the eye moist and protects it from dust. A bird's ears are round openings on either side of the head. In general, birds have a narrower range of hearing than human beings. In most birds the sense of smell is not important for survival.
Size
Birds vary greatly in size. The bee hummingbird of Cuba is generally accepted as the smallest living bird. It is 2 12 inches (6.3 centimeters) long and weighs about 110 ounce (less than 3 grams). The largest living bird is the ostrich. Ostriches can stand 8 feet (2.5 meters) tall and weigh 300 pounds (136 kilograms).
Other features
A bird's bones are hollow and very light. Birds also have a beak and a feature called a crop, which is a pouchlike enlargement of the throat. The crop is used to store food. The gizzard is a part of the stomach where digestive juices break down food. The neck of a bird moves more freely than that of any other animal. A flexible neck allows the bird to look out in all directions for approaching danger. The flexible neck also helps the bird catch food and preen its feathers.
Behavior
Birds communicate with one another by using many different sounds. For example, some baby chicks stop moving when their mother produces a danger call. A male bird will perch somewhere, such as on a telephone wire or tree branch, and sing loudly to inform other males that a certain territory belongs to him. The same song is also used in courtship to attract the female.
Birds keep their feathers clean and smooth. All birds like to bathe. Some even take dry baths in dust, sand, and snow. Such bathing may help get rid of pests in the feathers.
Some birds, such as falcons, live alone. Other birds are more social, such as the guanay cormorants of South America that nest in large groups.
Feeding habits
Many birds are insect-eaters. They have developed special abilities to catch insects. For example, some birds catch insects by probing for them with their long, sticky tongues. Others dig in the ground with their bills. Birds of prey have claws and hooked bills for feeding on larger animals. Herons have spearlike bills for catching fish. Some birds feed on plant material, such as seeds, fruit, or nectar. Many birds eat a wide variety of foods.
Reproduction
Each year, many species of birds return to their summer homes, choose their mates, build their nests, lay eggs, and rear their young. The number of eggs in a set varies from 1 to about 20. Nests may be a scrape in the sand or an elaborately woven hanging structure. A type of bird called the swift uses its saliva to hold together branches when making its nest.
Most birds sit on their eggs to hatch them. This process, called incubation, takes from 11 to 80 days. The length of time that parents care for young birds varies widely. Some young are capable of finding food for themselves almost immediately. Others depend entirely on their parents for food.
Birds and human beings
Humans have interacted with birds in various ways throughout history. In the mythology and literature of many cultures, birds are often featured as characters. Many people enjoy keeping birds as pets, and zoos in many cities import birds from different lands for people to see in person and learn about. Humans have also used birds for their own purposes. For instance, pigeons have long been bred and trained for carrying messages. Birds such as chickens and turkeys are often raised for their meat, and the eggs of certain birds are a source of food for many people.
Birds have also been valued for their feathers, which have been used for decoration since early times. Their use in the headdresses of Native Americans is well known. Ostrich farms have been created to produce the soft and fluffy ostrich feathers that are used to make fans. Large quills were once widely used for writing, and feathers have often been used on arrows.
Humans can have a negative impact on the bird population because of this interest. In the past many birds were killed for their feathers and quills. In addition, bird habitats are destroyed throughout the world when people cut down trees to create farmland, houses, and other buildings. Pollution also destroys bird habitats. When a habitat is destroyed, the birds are forced to look for a new place to live. Many birds do not survive this move, and in some cases, entire species die out.
Where birds live
Birds are found almost everywhere on Earth, from the Antarctic ice caps to tropical forests. There are more than 9,000 known species of birds.
Many birds migrate long distances between winter and summer homes in search of a constant food supply. For example, after nesting and raising their young, many European birds travel to Africa for the winter.
Physical features
Flight
Birds are able to fly because of their body structure and feathers. A flying bird's body is slender and tapers like a jet airplane. However, not all birds can fly. Penguins spend their time in the water and ostriches have undeveloped wings. Because of this, they must walk or run everywhere. Most birds alternate some walking and swimming with their flying.
Feathers
A bird's feathers protect it from rain, cold, and heat. Water slides off a bird's feathers without soaking through. Birds fluff out their feathers on cold days. These fluffed feathers hold a layer of warm air next to their skin. In hot weather birds flatten their feathers close to their body. This keeps their skin cool by preventing hot air from reaching it. The entire covering of feathers on a bird is called plumage. A bird's feathers wear out and are replaced in a process called molting. All birds molt at least once a year, usually in the summer or early fall. Birds also preen their feathers. Birds preen by using their bill to clean, rearrange, and apply oils to their feathers.
Coloring
In many species of birds the male is more brightly colored than the female. The dull color of the females helps them to remain hidden in their nest. In some cases, the brightly colored male perches a short distance away from the nest. In this way, the male bird draws the attention of enemies to himself and away from the eggs and young.
Metabolism
Like humans, birds are warm-blooded. This means that they have a constant body temperature that is not affected by the temperature of their surroundings. Their hearts beat faster than human hearts, however, and birds breathe more rapidly than humans. Because of this, birds have a high metabolism, meaning that they use up energy very quickly. Therefore, some small birds must eat almost constantly while they are awake.
Senses
Birds have very sharp eyesight. An American kestrel hovering 100 feet (30 meters) above a field can spot a grasshopper and drop directly on it. A thin transparent membrane extends across a bird's eyeball. This membrane keeps the eye moist and protects it from dust. A bird's ears are round openings on either side of the head. In general, birds have a narrower range of hearing than human beings. In most birds the sense of smell is not important for survival.
Size
Birds vary greatly in size. The bee hummingbird of Cuba is generally accepted as the smallest living bird. It is 2 12 inches (6.3 centimeters) long and weighs about 110 ounce (less than 3 grams). The largest living bird is the ostrich. Ostriches can stand 8 feet (2.5 meters) tall and weigh 300 pounds (136 kilograms).
Other features
A bird's bones are hollow and very light. Birds also have a beak and a feature called a crop, which is a pouchlike enlargement of the throat. The crop is used to store food. The gizzard is a part of the stomach where digestive juices break down food. The neck of a bird moves more freely than that of any other animal. A flexible neck allows the bird to look out in all directions for approaching danger. The flexible neck also helps the bird catch food and preen its feathers.
Behavior
Birds communicate with one another by using many different sounds. For example, some baby chicks stop moving when their mother produces a danger call. A male bird will perch somewhere, such as on a telephone wire or tree branch, and sing loudly to inform other males that a certain territory belongs to him. The same song is also used in courtship to attract the female.
Birds keep their feathers clean and smooth. All birds like to bathe. Some even take dry baths in dust, sand, and snow. Such bathing may help get rid of pests in the feathers.
Some birds, such as falcons, live alone. Other birds are more social, such as the guanay cormorants of South America that nest in large groups.
Feeding habits
Many birds are insect-eaters. They have developed special abilities to catch insects. For example, some birds catch insects by probing for them with their long, sticky tongues. Others dig in the ground with their bills. Birds of prey have claws and hooked bills for feeding on larger animals. Herons have spearlike bills for catching fish. Some birds feed on plant material, such as seeds, fruit, or nectar. Many birds eat a wide variety of foods.
Reproduction
Each year, many species of birds return to their summer homes, choose their mates, build their nests, lay eggs, and rear their young. The number of eggs in a set varies from 1 to about 20. Nests may be a scrape in the sand or an elaborately woven hanging structure. A type of bird called the swift uses its saliva to hold together branches when making its nest.
Most birds sit on their eggs to hatch them. This process, called incubation, takes from 11 to 80 days. The length of time that parents care for young birds varies widely. Some young are capable of finding food for themselves almost immediately. Others depend entirely on their parents for food.
Birds and human beings
Humans have interacted with birds in various ways throughout history. In the mythology and literature of many cultures, birds are often featured as characters. Many people enjoy keeping birds as pets, and zoos in many cities import birds from different lands for people to see in person and learn about. Humans have also used birds for their own purposes. For instance, pigeons have long been bred and trained for carrying messages. Birds such as chickens and turkeys are often raised for their meat, and the eggs of certain birds are a source of food for many people.
Birds have also been valued for their feathers, which have been used for decoration since early times. Their use in the headdresses of Native Americans is well known. Ostrich farms have been created to produce the soft and fluffy ostrich feathers that are used to make fans. Large quills were once widely used for writing, and feathers have often been used on arrows.
Humans can have a negative impact on the bird population because of this interest. In the past many birds were killed for their feathers and quills. In addition, bird habitats are destroyed throughout the world when people cut down trees to create farmland, houses, and other buildings. Pollution also destroys bird habitats. When a habitat is destroyed, the birds are forced to look for a new place to live. Many birds do not survive this move, and in some cases, entire species die out.
Scientist
07-10-2007, 09:01
Birds that pursue other animals for food are called birds of prey. They are also called raptors. Birds of prey are usually fairly large in size. They have good eyesight that helps them see their prey from far away. Their hooked beaks and sharp claws are useful for holding, carrying, and killing prey. Birds of prey can be found all over the world. Some common birds of prey are buzzards, eagles, falcons, hawks, ospreys, owls, and vultures.
Behavior
Most birds of prey hunt by sight during the day. They then sleep at night. Owls, however, hunt at night and sleep during the day.
Birds of prey eat many different kinds of animals. Some eat reptiles such as snakes and frogs. Others eat birds, insects, or rodents. A few birds of prey feast on carrion, which is the flesh of dead animals. Birds that only eat fish, such as penguins, pelicans, and storks, are generally not considered to be birds of prey.
Reproduction
Many birds of prey mate for life. They build nests in trees, on ledges of cliffs, or on the ground. Many lay only one egg at a time, and few lay more than four. Owls are an exception to this rule as they can lay up to 12 eggs at a time. The eggs are usually rounded ovals, white or greenish, and spotted. Occasionally they are completely covered with brown or red-brown pigment. The eggs hatch in the order in which they were laid.
Just after the birds have hatched, they usually receive a lot of attention from their parents. Later, parental attention is steadily reduced until the young are left alone except for brief feeding visits. The young birds make their first flights on their own, without the prodding of their parents.
Relationship to humans
Birds of prey are helpful to humans because they eat dead animals and control rodent populations. However, many of them are facing extinction. In some cases birds of prey are destroyed by humans because the birds are believed to kill small domestic animals. Birds of prey have also been harmed by the effects of human activity on their food sources and habitats. As the human population has grown, more and more trees have been cut down to provide land for farming. This has limited the number of areas where these birds can live. Birds of prey need a large amount of space for their territories so they do not have to compete with other birds for food.
Chemicals used to kill pests have also harmed birds of prey. This happens when the birds of prey eat animals that have earlier eaten plants containing these poisonous chemicals. The poisons in the animals cause the birds of prey to lay eggs with thin shells. These eggs can break before the young hatch. Therefore the birds of prey may have fewer chicks. This problem is made worse because birds of prey lay only a few eggs at one time.
Behavior
Most birds of prey hunt by sight during the day. They then sleep at night. Owls, however, hunt at night and sleep during the day.
Birds of prey eat many different kinds of animals. Some eat reptiles such as snakes and frogs. Others eat birds, insects, or rodents. A few birds of prey feast on carrion, which is the flesh of dead animals. Birds that only eat fish, such as penguins, pelicans, and storks, are generally not considered to be birds of prey.
Reproduction
Many birds of prey mate for life. They build nests in trees, on ledges of cliffs, or on the ground. Many lay only one egg at a time, and few lay more than four. Owls are an exception to this rule as they can lay up to 12 eggs at a time. The eggs are usually rounded ovals, white or greenish, and spotted. Occasionally they are completely covered with brown or red-brown pigment. The eggs hatch in the order in which they were laid.
Just after the birds have hatched, they usually receive a lot of attention from their parents. Later, parental attention is steadily reduced until the young are left alone except for brief feeding visits. The young birds make their first flights on their own, without the prodding of their parents.
Relationship to humans
Birds of prey are helpful to humans because they eat dead animals and control rodent populations. However, many of them are facing extinction. In some cases birds of prey are destroyed by humans because the birds are believed to kill small domestic animals. Birds of prey have also been harmed by the effects of human activity on their food sources and habitats. As the human population has grown, more and more trees have been cut down to provide land for farming. This has limited the number of areas where these birds can live. Birds of prey need a large amount of space for their territories so they do not have to compete with other birds for food.
Chemicals used to kill pests have also harmed birds of prey. This happens when the birds of prey eat animals that have earlier eaten plants containing these poisonous chemicals. The poisons in the animals cause the birds of prey to lay eggs with thin shells. These eggs can break before the young hatch. Therefore the birds of prey may have fewer chicks. This problem is made worse because birds of prey lay only a few eggs at one time.
Scientist
07-10-2007, 09:02
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The so-called American buffalo that used to roam by the millions on the North American plains is actually a bison. The American, or plains, bison is the largest land mammal in North America. The only other species, or type, of bison is the European bison, or wisent. The true buffalo are a different group of animals found in the warm regions of Africa and Asia. Both bison and buffalo belong to the scientific family Bovidae.
Where bison live
At one time, large herds of American bison roamed the area from Mexico to northern Canada and from the eastern United States to west of the Rocky Mountains. Most lived on open prairies. Today, however, the American bison is found mainly in protected areas such as national parks. The European bison used to range over Eastern Europe, but it is now found in restricted areas mostly in Poland and Russia. It lives in woodlands.
Physical features
Bison are large, powerful animals. A fully grown bull, or male bison, stands about 612 feet (2 meters) tall at the shoulder and weighs about 2,000 pounds (900 kilograms). An adult female is about 5 feet (1.5 meters) tall and weighs about 700 pounds (320 kilograms). The European bison is slightly larger than the American bison but is not as heavily built. A bison has a huge head and a hump at the shoulders. Two short horns curve upward. A female's horns are more slender than a male's.
A bison's fur is coarse, shaggy, and dark brown. It grows especially long on the head, neck, and shoulders and usually forms a beard on the chin. The hair on the bison's front is permanent, but the hair on its hind parts is shed each year, beginning in March. By early summer those parts are quite bare. For protection against insect bites, a bison wallows in mud or shallow ponds to cover its body with mud or clay. When the mud or clay dries in the sun, it forms a protective cover. By October new hair has grown on the hind parts. The fur is at its fullest in November and December.
Behavior
Bison prefer to eat grass and herbs, but they also eat twigs and leaves. They move around in small groups, or bands. A band of bison is usually made up of one or more females and several generations of their offspring. Adult males live somewhere outside a band's territory or form their own small groups. The cow, or female bison, usually gives birth to a single calf in May after about nine months of pregnancy. All members of the band protect the young.
Sometimes large herds form when dozens or even hundreds of bands come together. Herds of bison may make short seasonal migrations. They travel a few hundred miles southward in winter and then move back north when warmer weather returns.
Bison usually move with a plodding walk, but they also trot and run. Despite their size, they are agile and fast. They can run at speeds of 40 miles per hour (65 kilometers per hour).
Bison and humans
For the Plains Indians the American bison was the most important game animal. The Indians ate fresh bison meat or preserved the meat by drying and pounding it. Bison hides provided material for tepees and robes.
About 30 to 60 million bison roamed over North America when Europeans arrived in the 16th century. As white settlers moved westward in the 18th and 19th centuries, however, the number of bison dropped dramatically. The settlers killed millions of the animals for food, for hides, or just for sport. By the 1880s fewer than 1,000 American bison were left, most of them in Canada.
At the start of the 20th century, as the American bison neared extinction, cattlemen and conservationists came together to protect the remaining animals on government land. In the early 21st century there were as many as 200,000 American bison, and they were no longer in danger of extinction.
The European bison also came close to extinction. For centuries the animals have been protected on government lands in Poland. Today European bison are kept and bred in other countries as well. Some animals have been released into the wild. Their numbers remain low, however.
The so-called American buffalo that used to roam by the millions on the North American plains is actually a bison. The American, or plains, bison is the largest land mammal in North America. The only other species, or type, of bison is the European bison, or wisent. The true buffalo are a different group of animals found in the warm regions of Africa and Asia. Both bison and buffalo belong to the scientific family Bovidae.
Where bison live
At one time, large herds of American bison roamed the area from Mexico to northern Canada and from the eastern United States to west of the Rocky Mountains. Most lived on open prairies. Today, however, the American bison is found mainly in protected areas such as national parks. The European bison used to range over Eastern Europe, but it is now found in restricted areas mostly in Poland and Russia. It lives in woodlands.
Physical features
Bison are large, powerful animals. A fully grown bull, or male bison, stands about 612 feet (2 meters) tall at the shoulder and weighs about 2,000 pounds (900 kilograms). An adult female is about 5 feet (1.5 meters) tall and weighs about 700 pounds (320 kilograms). The European bison is slightly larger than the American bison but is not as heavily built. A bison has a huge head and a hump at the shoulders. Two short horns curve upward. A female's horns are more slender than a male's.
A bison's fur is coarse, shaggy, and dark brown. It grows especially long on the head, neck, and shoulders and usually forms a beard on the chin. The hair on the bison's front is permanent, but the hair on its hind parts is shed each year, beginning in March. By early summer those parts are quite bare. For protection against insect bites, a bison wallows in mud or shallow ponds to cover its body with mud or clay. When the mud or clay dries in the sun, it forms a protective cover. By October new hair has grown on the hind parts. The fur is at its fullest in November and December.
Behavior
Bison prefer to eat grass and herbs, but they also eat twigs and leaves. They move around in small groups, or bands. A band of bison is usually made up of one or more females and several generations of their offspring. Adult males live somewhere outside a band's territory or form their own small groups. The cow, or female bison, usually gives birth to a single calf in May after about nine months of pregnancy. All members of the band protect the young.
Sometimes large herds form when dozens or even hundreds of bands come together. Herds of bison may make short seasonal migrations. They travel a few hundred miles southward in winter and then move back north when warmer weather returns.
Bison usually move with a plodding walk, but they also trot and run. Despite their size, they are agile and fast. They can run at speeds of 40 miles per hour (65 kilometers per hour).
Bison and humans
For the Plains Indians the American bison was the most important game animal. The Indians ate fresh bison meat or preserved the meat by drying and pounding it. Bison hides provided material for tepees and robes.
About 30 to 60 million bison roamed over North America when Europeans arrived in the 16th century. As white settlers moved westward in the 18th and 19th centuries, however, the number of bison dropped dramatically. The settlers killed millions of the animals for food, for hides, or just for sport. By the 1880s fewer than 1,000 American bison were left, most of them in Canada.
At the start of the 20th century, as the American bison neared extinction, cattlemen and conservationists came together to protect the remaining animals on government land. In the early 21st century there were as many as 200,000 American bison, and they were no longer in danger of extinction.
The European bison also came close to extinction. For centuries the animals have been protected on government lands in Poland. Today European bison are kept and bred in other countries as well. Some animals have been released into the wild. Their numbers remain low, however.
Scientist
07-10-2007, 09:03
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There are many types of blackbirds—small birds whose name comes from the black color of the males' feathers. The best-known type is the red-winged blackbird. Other kinds of blackbirds include the Old World blackbird, the yellow-headed blackbird, and the grackles. Although crows and ravens also have black feathers, they do not belong to the blackbird family.
Where blackbirds live
Blackbirds make their nests in marshes, on dry prairies, or in dense evergreen forests. The Old World blackbird lives in woods and gardens throughout the warmer areas of Europe and Asia as well as in New Zealand and Australia. Most blackbirds, however, are found in North America. Red-winged blackbirds live in cattail marshes from Canada to the West Indies and Central America. The yellow-headed blackbird of the Western plains also nests in marshes. Grackles are found along the southern coasts of the Atlantic Ocean and the Gulf of Mexico.
Physical features
Blackbirds generally range from 8 to 16 inches (20 to 41 centimeters) in length. Red-winged blackbirds are about 8 inches (20 centimeters) long. Old World blackbirds are about 10 inches (25 centimeters) long. At about 16 inches (41 centimeters) and with a long tail, the male great-tailed grackle is the largest of the blackbirds.
Though the males are mostly black, blackbirds boast a variety of colored details. The male red-winged blackbird has yellow and red feathers on its shoulders. The female is brown and resembles a large sparrow. Male Old World blackbirds are all black, and the females are brown. Both have an orange bill and orange coloring around the eyes. The male yellow-headed blackbird has a bright yellow head and a black body; the female has a dull yellow head and gray-brown body. The male great-tailed grackle has black feathers with a purple or blue-green shine.
Behavior
Many blackbirds make loud squeaks and gurgling clucks while fluttering their wings, bobbing their bodies, and wagging their tails. Red-winged blackbirds chirp musical songs.
Most blackbirds eat insects. Blackbirds are a benefit to humans because they eat harmful insects such as crop-eating pests.
Blackbirds have a variety of nesting habits. Some build nests on the ground, others attach theirs to marsh plants, and some build them high above the ground in trees. Some blackbirds, including the tricolored blackbird and the common grackle, build their nests in colonies. Both the male and the female usually help feed the young.
There are many types of blackbirds—small birds whose name comes from the black color of the males' feathers. The best-known type is the red-winged blackbird. Other kinds of blackbirds include the Old World blackbird, the yellow-headed blackbird, and the grackles. Although crows and ravens also have black feathers, they do not belong to the blackbird family.
Where blackbirds live
Blackbirds make their nests in marshes, on dry prairies, or in dense evergreen forests. The Old World blackbird lives in woods and gardens throughout the warmer areas of Europe and Asia as well as in New Zealand and Australia. Most blackbirds, however, are found in North America. Red-winged blackbirds live in cattail marshes from Canada to the West Indies and Central America. The yellow-headed blackbird of the Western plains also nests in marshes. Grackles are found along the southern coasts of the Atlantic Ocean and the Gulf of Mexico.
Physical features
Blackbirds generally range from 8 to 16 inches (20 to 41 centimeters) in length. Red-winged blackbirds are about 8 inches (20 centimeters) long. Old World blackbirds are about 10 inches (25 centimeters) long. At about 16 inches (41 centimeters) and with a long tail, the male great-tailed grackle is the largest of the blackbirds.
Though the males are mostly black, blackbirds boast a variety of colored details. The male red-winged blackbird has yellow and red feathers on its shoulders. The female is brown and resembles a large sparrow. Male Old World blackbirds are all black, and the females are brown. Both have an orange bill and orange coloring around the eyes. The male yellow-headed blackbird has a bright yellow head and a black body; the female has a dull yellow head and gray-brown body. The male great-tailed grackle has black feathers with a purple or blue-green shine.
Behavior
Many blackbirds make loud squeaks and gurgling clucks while fluttering their wings, bobbing their bodies, and wagging their tails. Red-winged blackbirds chirp musical songs.
Most blackbirds eat insects. Blackbirds are a benefit to humans because they eat harmful insects such as crop-eating pests.
Blackbirds have a variety of nesting habits. Some build nests on the ground, others attach theirs to marsh plants, and some build them high above the ground in trees. Some blackbirds, including the tricolored blackbird and the common grackle, build their nests in colonies. Both the male and the female usually help feed the young.
Scientist
07-10-2007, 09:04
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One of the earliest voices of spring in North America is the bluebird's. Bluebirds got their name from the males' bright blue feathers. All bluebirds belong to the thrush family; different species, or types, include the common, mountain, and western bluebirds. The common bluebird is the state bird of Missouri and New York.
Where bluebirds live
Bluebirds are found in fields, orchards, and gardens in North America. Common, or eastern, bluebirds live east of the Rocky Mountains, from northeastern Canada to the state of Florida. During the winter months, they migrate south to the middle states and the coast of the Gulf of Mexico. The mountain, or Arctic, bluebird can be found in the mountains of western North America. In winter, mountain bluebirds live in the southern United States and Mexico. The western bluebird lives from western Nevada and Idaho to the Pacific coast and north to British Columbia. It spends its winters in Mexico.
Physical features
Bluebirds are about 7 inches (18 centimeters) long. The males are usually more colorful than the females. Different kinds of bluebirds have slightly different colors. Most males are blue with a chestnut-colored throat, breast, and sides. Females can be grayish blue or brownish gray.
Behavior
Bluebirds nest in enclosed spaces, such as a hollow tree, an abandoned woodpecker hole, a rotted fence post, a bird box, or even a mailbox. Bluebirds line the bottom of their nests with dry grasses. The female lays four to six bluish white eggs at a time.
Bluebirds eat mostly insects and some fruit. Their diet makes them helpful to farmers because they keep harmful insects away from crops.
One of the earliest voices of spring in North America is the bluebird's. Bluebirds got their name from the males' bright blue feathers. All bluebirds belong to the thrush family; different species, or types, include the common, mountain, and western bluebirds. The common bluebird is the state bird of Missouri and New York.
Where bluebirds live
Bluebirds are found in fields, orchards, and gardens in North America. Common, or eastern, bluebirds live east of the Rocky Mountains, from northeastern Canada to the state of Florida. During the winter months, they migrate south to the middle states and the coast of the Gulf of Mexico. The mountain, or Arctic, bluebird can be found in the mountains of western North America. In winter, mountain bluebirds live in the southern United States and Mexico. The western bluebird lives from western Nevada and Idaho to the Pacific coast and north to British Columbia. It spends its winters in Mexico.
Physical features
Bluebirds are about 7 inches (18 centimeters) long. The males are usually more colorful than the females. Different kinds of bluebirds have slightly different colors. Most males are blue with a chestnut-colored throat, breast, and sides. Females can be grayish blue or brownish gray.
Behavior
Bluebirds nest in enclosed spaces, such as a hollow tree, an abandoned woodpecker hole, a rotted fence post, a bird box, or even a mailbox. Bluebirds line the bottom of their nests with dry grasses. The female lays four to six bluish white eggs at a time.
Bluebirds eat mostly insects and some fruit. Their diet makes them helpful to farmers because they keep harmful insects away from crops.
Scientist
07-10-2007, 09:13
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The boa constrictor is a large snake that kills its prey by coiling around it so tightly that it cannot breathe. Despite this deadly strength, the boa constrictor has gained popularity as a pet because it is mild-mannered, easily tamed, and not poisonous. They are so well behaved that some farmers even keep them around their fields, barns, and storage bins to hunt the rats and mice that eat their grain.
Where boa constrictors live
Boa constrictors live in a variety of habitats throughout Central and South America, including both tropical rainforests and dry scrublands and grasslands. The largest boa constrictors are found in South America.
Physical characteristics
The thick, muscular bodies of boa constrictors grow to about 10 feet (3 meters) in length, but some have been measured at more than 18 feet (5.5 meters). Central American boas rarely reach a length of more than 8 feet (2.4 meters). Some boa constrictors may be red or silver. However, most have a brown and gray body marked with a pattern of brown and black triangles and ovals, with white borders and streaks. The long, triangular head of a boa constrictor has dark streaks from the eyes to the back of the jaw and another dark streak along the top.
Behavior
During the day the boa constrictor rests in tree hollows, old logs, and animal burrows. At night it hunts a wide variety of birds, reptiles, and mammals. It hunts most animals on the ground, but it also climbs into trees in search of birds.
Females give birth to litters of live young that measure from 1 to 2 feet (0.3 to 0.6 meter) long. Litters may include several dozen babies.
The boa constrictor is a large snake that kills its prey by coiling around it so tightly that it cannot breathe. Despite this deadly strength, the boa constrictor has gained popularity as a pet because it is mild-mannered, easily tamed, and not poisonous. They are so well behaved that some farmers even keep them around their fields, barns, and storage bins to hunt the rats and mice that eat their grain.
Where boa constrictors live
Boa constrictors live in a variety of habitats throughout Central and South America, including both tropical rainforests and dry scrublands and grasslands. The largest boa constrictors are found in South America.
Physical characteristics
The thick, muscular bodies of boa constrictors grow to about 10 feet (3 meters) in length, but some have been measured at more than 18 feet (5.5 meters). Central American boas rarely reach a length of more than 8 feet (2.4 meters). Some boa constrictors may be red or silver. However, most have a brown and gray body marked with a pattern of brown and black triangles and ovals, with white borders and streaks. The long, triangular head of a boa constrictor has dark streaks from the eyes to the back of the jaw and another dark streak along the top.
Behavior
During the day the boa constrictor rests in tree hollows, old logs, and animal burrows. At night it hunts a wide variety of birds, reptiles, and mammals. It hunts most animals on the ground, but it also climbs into trees in search of birds.
Females give birth to litters of live young that measure from 1 to 2 feet (0.3 to 0.6 meter) long. Litters may include several dozen babies.
Scientist
07-10-2007, 09:22
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
One of the tallest of all dinosaurs, Brachiosaurus was built something like an enormous elephant with an extremely long neck. This dinosaur was tall enough to have looked over the top of a modern four-story building. The name Brachiosaurus means “arm lizard” in Latin. Scientists call it this because of its long front legs. Brachiosaurus belongs to the group of dinosaurs known as sauropods, which also includes Apatosaurus and Diplodocus. The sauropods were large, plant-eating dinosaurs with long necks, massive bodies, and four pillarlike legs to support the body.
Where and when Brachiosaurus lived
Brachiosaurus lived about 150 to 130 million years ago, in the late part of the geologic period known as the Jurassic and the early part of the Cretaceous. Remains of Brachiosaurus have been found in Europe and Africa, as well as in Colorado, Wyoming, and Utah in North America. Scientists once believed that Brachiosaurus, like other large sauropod dinosaurs, needed to live in water to support its massive weight. They now agree that Brachiosaurus was primarily a land animal. Its strong but lightweight bones were able to support it without the help of water. Brachiosaurus lived in areas with much plant life, especially tall trees.
Physical features
Brachiosaurus is the largest and heaviest sauropod dinosaur for which a complete skeleton has been discovered. This dinosaur could reach more than 75 feet (23 meters) in length and weighed up to 80 tons. It stood about 43 feet (13 meters) tall from its head to the ground. The most striking features of Brachiosaurus were its sloped back and its extremely long neck. Its front legs were longer than its back legs, which was a unique feature among dinosaurs. Brachiosaurus also had a relatively short tail. Its dome-shaped head was small and its snout was somewhat flat. Its nostrils were fairly large and were located near the top of its head. Brachiosaurus had a few dozen pencil-like teeth.
Behavior
Brachiosaurus was a plant-eating dinosaur. Its long neck allowed it to feed from the tops of the highest trees, where other dinosaurs could not reach. Scientists believe that Brachiosaurus also fed on low-lying ground plants, such as ferns. Like other sauropod dinosaurs, Brachiosaurus had small stones in its stomach to help it grind up the plants that it ate. Brachiosaurus lived and traveled in herds. Scientists believe that Brachiosaurus could travel at speeds of about 12 to 19 miles per hour (19 to 31 kilometers per hour). Its immense size and weight, as well as sharp claws on its feet, protected it from meat-eating dinosaurs. Its tremendous height also allowed Brachiosaurus to watch for enemies coming from miles away. Young Brachiosaurus probably stayed in the center of the herd for protection. Brachiosaurus, like most other dinosaurs, reproduced by laying eggs.
One of the tallest of all dinosaurs, Brachiosaurus was built something like an enormous elephant with an extremely long neck. This dinosaur was tall enough to have looked over the top of a modern four-story building. The name Brachiosaurus means “arm lizard” in Latin. Scientists call it this because of its long front legs. Brachiosaurus belongs to the group of dinosaurs known as sauropods, which also includes Apatosaurus and Diplodocus. The sauropods were large, plant-eating dinosaurs with long necks, massive bodies, and four pillarlike legs to support the body.
Where and when Brachiosaurus lived
Brachiosaurus lived about 150 to 130 million years ago, in the late part of the geologic period known as the Jurassic and the early part of the Cretaceous. Remains of Brachiosaurus have been found in Europe and Africa, as well as in Colorado, Wyoming, and Utah in North America. Scientists once believed that Brachiosaurus, like other large sauropod dinosaurs, needed to live in water to support its massive weight. They now agree that Brachiosaurus was primarily a land animal. Its strong but lightweight bones were able to support it without the help of water. Brachiosaurus lived in areas with much plant life, especially tall trees.
Physical features
Brachiosaurus is the largest and heaviest sauropod dinosaur for which a complete skeleton has been discovered. This dinosaur could reach more than 75 feet (23 meters) in length and weighed up to 80 tons. It stood about 43 feet (13 meters) tall from its head to the ground. The most striking features of Brachiosaurus were its sloped back and its extremely long neck. Its front legs were longer than its back legs, which was a unique feature among dinosaurs. Brachiosaurus also had a relatively short tail. Its dome-shaped head was small and its snout was somewhat flat. Its nostrils were fairly large and were located near the top of its head. Brachiosaurus had a few dozen pencil-like teeth.
Behavior
Brachiosaurus was a plant-eating dinosaur. Its long neck allowed it to feed from the tops of the highest trees, where other dinosaurs could not reach. Scientists believe that Brachiosaurus also fed on low-lying ground plants, such as ferns. Like other sauropod dinosaurs, Brachiosaurus had small stones in its stomach to help it grind up the plants that it ate. Brachiosaurus lived and traveled in herds. Scientists believe that Brachiosaurus could travel at speeds of about 12 to 19 miles per hour (19 to 31 kilometers per hour). Its immense size and weight, as well as sharp claws on its feet, protected it from meat-eating dinosaurs. Its tremendous height also allowed Brachiosaurus to watch for enemies coming from miles away. Young Brachiosaurus probably stayed in the center of the herd for protection. Brachiosaurus, like most other dinosaurs, reproduced by laying eggs.
Scientist
07-10-2007, 09:24
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Although the North American bison is often called a buffalo, true buffalo come from much warmer lands in Asia and Africa. Along with bison, buffalo belong to the scientific family Bovidae.
Where buffalo live
The several types of buffalo are native to South and Southeast Asia and much of Africa. As people from those regions spread throughout the world they brought buffalo with them. Today the animals can be found in Europe, Australia, and South and Central America as well as Asia and Africa.
The Indian, or Asian water, buffalo lives in tall grasses close to bodies of water. It loves to lie in water or wallow in mud to keep flies away as well as to keep cool. The Cape, or African, buffalo lives in open or scrub-covered plains and open forests. Other types live in dense forests.
Physical features
Buffalo are heavily built animals. They range in size from the anoa, which stands about 3 feet (1 meter) tall, to the Asian water buffalo, which can reach a height of more than 5 feet (1.5 meters). All buffalo have horns, although the size and shape of the horns can vary greatly. The Cape buffalo has heavy horns that typically curve downward, then up and inward; in males the two horns meet to form a shield that covers the whole top of the head. The Asian water buffalo has horns that curve outward and backward and may reach 4 feet (1.2 meters) across. The animals can also vary in color. Many are black, though they may have patches of white, and one African type is reddish in color.
Behavior
Except for the anoa, buffalo in the wild travel and live in herds. They spend a great deal of time grazing on grasses and digesting their food. Buffalo are ruminants, which means that they digest their food by swallowing it, regurgitating it (bringing it back up from the stomach), and then chewing it again in a form called cud. Female buffalo give birth to one or two young 10 or 11 months after mating.
Buffalo and humans
The Asian water buffalo has been domesticated, or tamed for use by humans, for thousands of years. People value it as a beast of burden that can pull or carry things on its broad back. It is accustomed to wet conditions and for that reason is employed in flooded rice fields. People use buffalo milk and meat for food. In addition, people make leather products from buffalo hides.
Though the domestic water buffalo remains widespread, the number of buffalo in the wild is decreasing. Farmers have taken over some of the lands where wild buffalo live. Humans have hunted the animals in large numbers for food and for their hides. Diseases spread by domestic animals have also decreased the population of wild buffalo.
Although the North American bison is often called a buffalo, true buffalo come from much warmer lands in Asia and Africa. Along with bison, buffalo belong to the scientific family Bovidae.
Where buffalo live
The several types of buffalo are native to South and Southeast Asia and much of Africa. As people from those regions spread throughout the world they brought buffalo with them. Today the animals can be found in Europe, Australia, and South and Central America as well as Asia and Africa.
The Indian, or Asian water, buffalo lives in tall grasses close to bodies of water. It loves to lie in water or wallow in mud to keep flies away as well as to keep cool. The Cape, or African, buffalo lives in open or scrub-covered plains and open forests. Other types live in dense forests.
Physical features
Buffalo are heavily built animals. They range in size from the anoa, which stands about 3 feet (1 meter) tall, to the Asian water buffalo, which can reach a height of more than 5 feet (1.5 meters). All buffalo have horns, although the size and shape of the horns can vary greatly. The Cape buffalo has heavy horns that typically curve downward, then up and inward; in males the two horns meet to form a shield that covers the whole top of the head. The Asian water buffalo has horns that curve outward and backward and may reach 4 feet (1.2 meters) across. The animals can also vary in color. Many are black, though they may have patches of white, and one African type is reddish in color.
Behavior
Except for the anoa, buffalo in the wild travel and live in herds. They spend a great deal of time grazing on grasses and digesting their food. Buffalo are ruminants, which means that they digest their food by swallowing it, regurgitating it (bringing it back up from the stomach), and then chewing it again in a form called cud. Female buffalo give birth to one or two young 10 or 11 months after mating.
Buffalo and humans
The Asian water buffalo has been domesticated, or tamed for use by humans, for thousands of years. People value it as a beast of burden that can pull or carry things on its broad back. It is accustomed to wet conditions and for that reason is employed in flooded rice fields. People use buffalo milk and meat for food. In addition, people make leather products from buffalo hides.
Though the domestic water buffalo remains widespread, the number of buffalo in the wild is decreasing. Farmers have taken over some of the lands where wild buffalo live. Humans have hunted the animals in large numbers for food and for their hides. Diseases spread by domestic animals have also decreased the population of wild buffalo.
Scientist
07-10-2007, 09:25
Zebra swallowtail butterfly
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Luna moth
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Known for their brightly or strikingly colored wings, butterflies and moths are flying insects that come from caterpillars. There are as many as 100,000 different types of butterflies and moths throughout the world.
Where butterflies and moths live
Butterflies and moths are found in temperate regions, snowy mountains, deserts, and jungles. In fact, butterflies and moths live on every continent except Antarctica.
Physical features
Like all insects, butterflies and moths have three pairs of legs. Their bodies are divided into three sections: the head, thorax, and abdomen. On either side of the head is a large compound eye. The compound eyes are very efficient for distinguishing movement. They cannot, however, see distant objects clearly. Some butterflies and moths have very sharp hearing and sense of smell. They also have a good sense of taste, especially for sugars.
There are two pairs of wings on the thorax, or middle section of the body. The pair in front is usually the larger of the two. The wings, body, and legs are all covered with dustlike scales that come off when handled.
Butterflies and moths vary greatly in size. The smallest moths have wing expanses as small as about 16100 inch (4 millimeters), while the largest have wingspans of about 1 foot (nearly 30 centimeters).
Although butterflies and moths have similar appearances, they are different from each other in many ways. The best way to tell them apart is to examine their antennae, or feelers. Butterfly antennae are slender, and the ends are rounded into little knobs. Moth antennae lack these knobs. Moth feelers may look like tiny feathers, and some are threadlike.
Butterflies are usually brightly or strikingly colored. Most moths have a duller color, a stouter body, and smaller wings than butterflies. Butterflies rest with their wings held upright over their backs; moths rest with their wings outspread. Most butterflies fly during the daytime, while moths generally fly at night.
Skippers are insects that have some characteristics of both butterflies and moths. Their bodies resemble moths. When at rest, however, they hold their wings upright like butterflies. Skippers are generally small. They get their name because they fly with quick movements from place to place.
Behavior
Butterflies and moths feed on the nectar of flowers and on other plant liquids. Some species eat mosses, ferns, and lichens. Others may feed on cones and fruits and their seeds. Many also feed on dead and decaying plant matter.
Some butterflies and moths are famous for the fact that they travel from place to place. Several species in Europe and North America migrate to different regions based on the seasons. In North America the monarch butterfly lives as far north as southern Canada during the summer. In the fall these butterflies travel to California or Mexico, where they spend the winter. They then return to their summer homes in the spring. Unlike birds, they do not make the trip more than once since butterflies do not live longer than a year.
Life cycle
Butterflies and moths go through four stages of development: egg, larva (caterpillar), pupa (chrysalis), and adult (imago). The process of changing from one stage to the next is known as metamorphosis.
First, the female lays many eggs. Caterpillars hatch from these tiny larvae. The caterpillar then sheds its skin many times in a process called molting, until it is ready to turn into a pupa. The pupa is a resting stage, where the future butterfly lies encased in a tough, flexible shell. During this stage the organs and other tissues of the caterpillar break down and are replaced by wings, legs, and other parts of the adult.
In the final stage, the adult emerges from the pupa. At this point it is wet and its wings are soft and limp. It slowly fans the wings to pump air into the veins. Gradually the wings expand and harden. In a few hours the adult is ready to fly and seek a mate. Most adults live from four to six weeks. Some live only a few days, while others may live as long as ten months.
Defenses
Butterflies and moths have many enemies. In fact, they are a favorite food of birds. To survive, some species have natural protections. For example, the monarch butterfly has a foul taste and odor and is avoided by birds. The viceroy butterfly looks exactly like the monarch, only smaller. Because birds mistake viceroy butterflies for monarch butterflies, the birds leave the viceroy butterflies alone too.
Other species have unusual markings that frighten away birds. In addition, many butterflies and moths at rest look like dead leaves or the twigs and bark of trees. Therefore, they are difficult for birds to spot.
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Luna moth
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Known for their brightly or strikingly colored wings, butterflies and moths are flying insects that come from caterpillars. There are as many as 100,000 different types of butterflies and moths throughout the world.
Where butterflies and moths live
Butterflies and moths are found in temperate regions, snowy mountains, deserts, and jungles. In fact, butterflies and moths live on every continent except Antarctica.
Physical features
Like all insects, butterflies and moths have three pairs of legs. Their bodies are divided into three sections: the head, thorax, and abdomen. On either side of the head is a large compound eye. The compound eyes are very efficient for distinguishing movement. They cannot, however, see distant objects clearly. Some butterflies and moths have very sharp hearing and sense of smell. They also have a good sense of taste, especially for sugars.
There are two pairs of wings on the thorax, or middle section of the body. The pair in front is usually the larger of the two. The wings, body, and legs are all covered with dustlike scales that come off when handled.
Butterflies and moths vary greatly in size. The smallest moths have wing expanses as small as about 16100 inch (4 millimeters), while the largest have wingspans of about 1 foot (nearly 30 centimeters).
Although butterflies and moths have similar appearances, they are different from each other in many ways. The best way to tell them apart is to examine their antennae, or feelers. Butterfly antennae are slender, and the ends are rounded into little knobs. Moth antennae lack these knobs. Moth feelers may look like tiny feathers, and some are threadlike.
Butterflies are usually brightly or strikingly colored. Most moths have a duller color, a stouter body, and smaller wings than butterflies. Butterflies rest with their wings held upright over their backs; moths rest with their wings outspread. Most butterflies fly during the daytime, while moths generally fly at night.
Skippers are insects that have some characteristics of both butterflies and moths. Their bodies resemble moths. When at rest, however, they hold their wings upright like butterflies. Skippers are generally small. They get their name because they fly with quick movements from place to place.
Behavior
Butterflies and moths feed on the nectar of flowers and on other plant liquids. Some species eat mosses, ferns, and lichens. Others may feed on cones and fruits and their seeds. Many also feed on dead and decaying plant matter.
Some butterflies and moths are famous for the fact that they travel from place to place. Several species in Europe and North America migrate to different regions based on the seasons. In North America the monarch butterfly lives as far north as southern Canada during the summer. In the fall these butterflies travel to California or Mexico, where they spend the winter. They then return to their summer homes in the spring. Unlike birds, they do not make the trip more than once since butterflies do not live longer than a year.
Life cycle
Butterflies and moths go through four stages of development: egg, larva (caterpillar), pupa (chrysalis), and adult (imago). The process of changing from one stage to the next is known as metamorphosis.
First, the female lays many eggs. Caterpillars hatch from these tiny larvae. The caterpillar then sheds its skin many times in a process called molting, until it is ready to turn into a pupa. The pupa is a resting stage, where the future butterfly lies encased in a tough, flexible shell. During this stage the organs and other tissues of the caterpillar break down and are replaced by wings, legs, and other parts of the adult.
In the final stage, the adult emerges from the pupa. At this point it is wet and its wings are soft and limp. It slowly fans the wings to pump air into the veins. Gradually the wings expand and harden. In a few hours the adult is ready to fly and seek a mate. Most adults live from four to six weeks. Some live only a few days, while others may live as long as ten months.
Defenses
Butterflies and moths have many enemies. In fact, they are a favorite food of birds. To survive, some species have natural protections. For example, the monarch butterfly has a foul taste and odor and is avoided by birds. The viceroy butterfly looks exactly like the monarch, only smaller. Because birds mistake viceroy butterflies for monarch butterflies, the birds leave the viceroy butterflies alone too.
Other species have unusual markings that frighten away birds. In addition, many butterflies and moths at rest look like dead leaves or the twigs and bark of trees. Therefore, they are difficult for birds to spot.
Scientist
07-10-2007, 09:26
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Buzzards are carnivorous birds, which means that they eat other animals for food. They are in the same family of birds as hawks and are considered birds of prey. The best-known buzzard is the common or true buzzard.
Where buzzards live
The common buzzard is found from Scandinavia in the north to the Mediterranean Sea in the south. Other species, or kinds, range over much of North America, Eurasia, and northern Africa. They live in hills, wooded valleys, and farmland with scattered woods.
Physical characteristics
When in flight, buzzards can be recognized by their broad wings and large rounded tails. Their wingspan may be anywhere between 48 and 60 inches (120 to 150 centimeters). They fly with slow, heavy wing beats and soar gracefully. The feathers of most buzzards are dark brown above and white or light brown below. The tail and underside of the wings are usually striped. The color of these birds varies.
Behavior
Buzzards eat insects and small mammals. They also occasionally attack other birds. They are slow fliers, so they do not usually catch their prey on the move. Instead, buzzards perch motionless on a branch while waiting patiently for a rabbit, rat, or mouse to pass beneath it. Then they swoop down and surprise their prey.
Buzzards build big nests, usually in a tree or on a cliff. They build these nests with sticks and line them with softer materials. They generally lay two to five eggs. The eggs are white and brown.
Buzzards are carnivorous birds, which means that they eat other animals for food. They are in the same family of birds as hawks and are considered birds of prey. The best-known buzzard is the common or true buzzard.
Where buzzards live
The common buzzard is found from Scandinavia in the north to the Mediterranean Sea in the south. Other species, or kinds, range over much of North America, Eurasia, and northern Africa. They live in hills, wooded valleys, and farmland with scattered woods.
Physical characteristics
When in flight, buzzards can be recognized by their broad wings and large rounded tails. Their wingspan may be anywhere between 48 and 60 inches (120 to 150 centimeters). They fly with slow, heavy wing beats and soar gracefully. The feathers of most buzzards are dark brown above and white or light brown below. The tail and underside of the wings are usually striped. The color of these birds varies.
Behavior
Buzzards eat insects and small mammals. They also occasionally attack other birds. They are slow fliers, so they do not usually catch their prey on the move. Instead, buzzards perch motionless on a branch while waiting patiently for a rabbit, rat, or mouse to pass beneath it. Then they swoop down and surprise their prey.
Buzzards build big nests, usually in a tree or on a cliff. They build these nests with sticks and line them with softer materials. They generally lay two to five eggs. The eggs are white and brown.
Scientist
07-10-2007, 09:55
Sometimes called the “ship of the desert,” the camel is a large mammal that is well suited to living and working in hot, dry deserts. Camels are known for their humps, which can nourish the animal for several days when it does not have food or water.
Where camels live
Camels originated in North America about 40 million years ago. By about 1 million years ago they had spread to South America and Asia. Camels later vanished from North America. Relatives of the camel, such as the guanaco, vicuña, llama, and alpaca, now live in South America.
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The Bactrian, or Asian, camel is found throughout the highlands of Central Asia. Although this camel is largely domesticated, or tamed to help humans, small herds of wild Bactrians are still found in southwestern Mongolia and northwestern China.
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The dromedary, or Arabian, camel is found in North Africa, the Middle East, and India. This camel once roamed wild but is now found only in domestication. Groups of dromedaries, however, are often left on their own for up to five months. The dromedary has been imported into many parts of the world, including the United States and Australia.
Physical features
The camel's most striking feature is the large hump (for the dromedary) or two large humps (for the Bactrian) on its back. The hump is made of fat and muscle and does not have any bone. When a camel is well fed and given enough water, the hump remains erect. If the animal goes without food and water for a period of time, the fat in its hump can nourish it for several days. In this case, the hump becomes limp and leans to one side.
When a camel stands on its very long legs, its hump can reach a height of 7 feet (about 2 meters) above the ground. The animal weighs up to 1,500 pounds (680 kilograms). It has a long, thin neck, a small head without horns or antlers, and a split upper lip. Each foot consists of two toes. Each toe has a hoof at end of it. The soft feet are well suited for walking on sand or snow. Horny pads on a camel's chest and knees support its weight when it kneels. The camel's body is covered with a scruffy, sand-colored coat of hair. A thick fringe of hair also hangs from the long, curved neck.
Camels are well adapted to the desert and other harsh environments. A long, double row of eyelashes protects the animal's eyes from sandstorms and the glare of the desert sun. The nostrils can open wide to draw breath, or they can close to keep out blowing sand. The camel also has a keen sense of sight and smell. It has long jaws with sharp teeth. A camel's lower jaw swings sideways as the animal chews.
Behavior
Camels can survive on the coarsest of vegetation. They can feed on thorny plants, the leaves and twigs of shrubs, and dried grasses. They can also go for days or even months without water. Camels can carry up to 1,000 pounds (450 kilograms), though a more typical load is about one third of that.
Life cycle
The female camel produces one calf at a time. The newborn calf stands about 3 feet (1 meter) high on long, thin, wobbly legs. It can follow its mother to pasture just one day after birth.
By their third year camels have grown big enough to carry heavy loads. They can bear such loads for 15 to 20 years and then do lighter work until they are about 30 years old. The life span of a camel is generally 30 to 40 years.
Other uses of the camel
Camel milk and meat are valuable sources of nourishment for desert dwellers. Camel hair can be used to make tents, blankets, rugs, clothing, rope, and cord. Dried camel droppings are useful as fuel for cooking fires. The hide of the animal can be used for making sandals, water bags, and other necessary articles.
Where camels live
Camels originated in North America about 40 million years ago. By about 1 million years ago they had spread to South America and Asia. Camels later vanished from North America. Relatives of the camel, such as the guanaco, vicuña, llama, and alpaca, now live in South America.
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The Bactrian, or Asian, camel is found throughout the highlands of Central Asia. Although this camel is largely domesticated, or tamed to help humans, small herds of wild Bactrians are still found in southwestern Mongolia and northwestern China.
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The dromedary, or Arabian, camel is found in North Africa, the Middle East, and India. This camel once roamed wild but is now found only in domestication. Groups of dromedaries, however, are often left on their own for up to five months. The dromedary has been imported into many parts of the world, including the United States and Australia.
Physical features
The camel's most striking feature is the large hump (for the dromedary) or two large humps (for the Bactrian) on its back. The hump is made of fat and muscle and does not have any bone. When a camel is well fed and given enough water, the hump remains erect. If the animal goes without food and water for a period of time, the fat in its hump can nourish it for several days. In this case, the hump becomes limp and leans to one side.
When a camel stands on its very long legs, its hump can reach a height of 7 feet (about 2 meters) above the ground. The animal weighs up to 1,500 pounds (680 kilograms). It has a long, thin neck, a small head without horns or antlers, and a split upper lip. Each foot consists of two toes. Each toe has a hoof at end of it. The soft feet are well suited for walking on sand or snow. Horny pads on a camel's chest and knees support its weight when it kneels. The camel's body is covered with a scruffy, sand-colored coat of hair. A thick fringe of hair also hangs from the long, curved neck.
Camels are well adapted to the desert and other harsh environments. A long, double row of eyelashes protects the animal's eyes from sandstorms and the glare of the desert sun. The nostrils can open wide to draw breath, or they can close to keep out blowing sand. The camel also has a keen sense of sight and smell. It has long jaws with sharp teeth. A camel's lower jaw swings sideways as the animal chews.
Behavior
Camels can survive on the coarsest of vegetation. They can feed on thorny plants, the leaves and twigs of shrubs, and dried grasses. They can also go for days or even months without water. Camels can carry up to 1,000 pounds (450 kilograms), though a more typical load is about one third of that.
Life cycle
The female camel produces one calf at a time. The newborn calf stands about 3 feet (1 meter) high on long, thin, wobbly legs. It can follow its mother to pasture just one day after birth.
By their third year camels have grown big enough to carry heavy loads. They can bear such loads for 15 to 20 years and then do lighter work until they are about 30 years old. The life span of a camel is generally 30 to 40 years.
Other uses of the camel
Camel milk and meat are valuable sources of nourishment for desert dwellers. Camel hair can be used to make tents, blankets, rugs, clothing, rope, and cord. Dried camel droppings are useful as fuel for cooking fires. The hide of the animal can be used for making sandals, water bags, and other necessary articles.
Scientist
07-10-2007, 09:56
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A canary is a type of bird that belongs to the finch family. It has become a popular household pet around the world. Canaries became cage birds in the 16th century, when they were first brought from the Canary Islands of Spain to Italy. Over time, humans have been able to breed at least 50 different kinds of canaries.
Where canaries live
The canary is native to the Canary, Azores, and Madeira islands. In North America, “wild canaries” are also known as American goldfinches and yellow warblers. Both of these birds look like pet canaries. Breeders in the United States, France, Belgium, England, and Scotland have helped develop the canary's color, shape, and song.
Physical features
In the wild, canaries measure about 5 12 inches (14 centimeters) in length. They are dull green with a yellow breast. Canaries kept as pets differ in size, form, feather color, and song. Breeders work to develop these characteristics among the different kinds of canaries.
The American Singer is a very popular type of canary. It is usually yellow. One of the most graceful canaries is the Yorkshire canary. It has a long, slim body. The average life span of a caged canary is ten to 15 years.
Behavior
The behavior and song of a canary vary depending on the type of breed. A roller canary trills almost continuously, and its songs are very controlled and complex. Another kind of canary, called a chopper, has a loud trill.
A canary is a type of bird that belongs to the finch family. It has become a popular household pet around the world. Canaries became cage birds in the 16th century, when they were first brought from the Canary Islands of Spain to Italy. Over time, humans have been able to breed at least 50 different kinds of canaries.
Where canaries live
The canary is native to the Canary, Azores, and Madeira islands. In North America, “wild canaries” are also known as American goldfinches and yellow warblers. Both of these birds look like pet canaries. Breeders in the United States, France, Belgium, England, and Scotland have helped develop the canary's color, shape, and song.
Physical features
In the wild, canaries measure about 5 12 inches (14 centimeters) in length. They are dull green with a yellow breast. Canaries kept as pets differ in size, form, feather color, and song. Breeders work to develop these characteristics among the different kinds of canaries.
The American Singer is a very popular type of canary. It is usually yellow. One of the most graceful canaries is the Yorkshire canary. It has a long, slim body. The average life span of a caged canary is ten to 15 years.
Behavior
The behavior and song of a canary vary depending on the type of breed. A roller canary trills almost continuously, and its songs are very controlled and complex. Another kind of canary, called a chopper, has a loud trill.
Scientist
07-10-2007, 09:57
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A songbird of the finch family, the cardinal is sometimes called the redbird because of its striking color. Its loud, clear whistling song can be heard year-round in gardens and open woodlands. The cardinal is the state bird of Illinois, Indiana, Kentucky, North Carolina, Ohio, Virginia, and West Virginia.
Where cardinals live
Cardinals are found in North America east of the Rocky Mountains. They are especially abundant in the southeastern United States. Over the years, their range has extended farther into the northern United States. Cardinals do not migrate but instead spend the winter in their nesting areas.
Cardinals like brushy thickets and tangles. However, they also live in urban areas where shrubbery offers protection. They usually build their nests in bushes within a few feet of the ground. These nests are loosely built structures of twigs, leaves, bark, and grasses.
Physical characteristics
The cardinal is about 8 inches (20 centimeters) long, a little smaller than a robin. The male is easy to identify with its red crest and feathers and black face markings. The female and young have gray-brown backs and dull red wings, tail, and crest.
Behavior
Cardinals feed on insects and thus are good for pest control. They also eat seeds and wild fruits.
Female cardinals lay two to four eggs. They are bluish white with brown spots and hatch in 12 days. Baby cardinals remain in the nest for about ten days. The male cares for the young after they leave the nest, while the female prepares for the next family.
A songbird of the finch family, the cardinal is sometimes called the redbird because of its striking color. Its loud, clear whistling song can be heard year-round in gardens and open woodlands. The cardinal is the state bird of Illinois, Indiana, Kentucky, North Carolina, Ohio, Virginia, and West Virginia.
Where cardinals live
Cardinals are found in North America east of the Rocky Mountains. They are especially abundant in the southeastern United States. Over the years, their range has extended farther into the northern United States. Cardinals do not migrate but instead spend the winter in their nesting areas.
Cardinals like brushy thickets and tangles. However, they also live in urban areas where shrubbery offers protection. They usually build their nests in bushes within a few feet of the ground. These nests are loosely built structures of twigs, leaves, bark, and grasses.
Physical characteristics
The cardinal is about 8 inches (20 centimeters) long, a little smaller than a robin. The male is easy to identify with its red crest and feathers and black face markings. The female and young have gray-brown backs and dull red wings, tail, and crest.
Behavior
Cardinals feed on insects and thus are good for pest control. They also eat seeds and wild fruits.
Female cardinals lay two to four eggs. They are bluish white with brown spots and hatch in 12 days. Baby cardinals remain in the nest for about ten days. The male cares for the young after they leave the nest, while the female prepares for the next family.
Scientist
07-10-2007, 09:58
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Cats have fascinated humans for thousands of years. People have prized them as hunters and companions, worshiped them as gods, and sacrificed them as demons. They often have been used as symbols of beauty, grace, mystery, and power. Cats are members of a flesh-eating family of animals that includes the lion, tiger, jaguar, leopard, puma, cheetah, and domestic cat, or house cat. The domestic cat (species Felis catus) is a member of the larger cat family Felidae. This article discusses the domestic cat.
Form and structure
Members of the cat family are quite easy to identify. They differ widely in size, color, and markings, but they all look “catlike.” They have long, rather slender but powerfully built bodies. Domestic cats are very different from the larger cats, in coat as well as in size. Male domestic cats may reach 28 inches (71 centimeters), but 21 inches (51 centimeters) is a more usual length for females. Most female domestic cats weigh between 6 and 10 pounds (2.5 and 4.5 kilograms) while males weigh between 10 and 15 pounds (4.5 and 6.8 kilograms). The British shorthair cat may weigh up to 28 pounds (13 kilograms). Most house cats, including the Siamese and Abyssinian, are shorthaired, but the Persian has a long, thick coat. The rex, a British breed, has a curly coat. The domestic cat may be black, white, brown, gray, yellow, red, orange, stripped (tabby), mixed white, black, and yellow (tortoiseshell), or marked with patches of color (calico).
Claws and teeth
The cat is equipped to be an efficient hunter. It has strong, sharp retractile claws, which are capable of being drawn back or in, and strong, sharp teeth. The jaws of a cat are short but they, too, are extremely strong. They clamp down upon prey with enough power to crush bones. The cat's teeth are used to grab and hold prey. The sharp molars function like scissors and cut food into small pieces.
Eyes, ears, and whiskers
The cat's large and prominent eyes are placed well forward on the head. The size and position of the eyes permit as much light as possible to enter them, which ensures a large field of vision—important for hunting and night prowling. The cat's hearing also is extremely sensitive. The triangular ears can rotate rapidly to identify the source of a sound. A cat can detect many sounds that humans cannot hear. In the cat, as in humans, the inner ear contains a mechanism for maintaining body balance. It is this mechanism that lets the animal land on its feet when it falls.
A cat's whiskers serve as delicate sense organs of touch. They allow the cat to feel its way around. Four rows of stiff whiskers grow on the upper lip on each side of the nose. Small groups of whiskers also grow on other parts of the body including above each eye, on both cheeks, and on the backs of the front paws.
The tongue
A cat's tongue is rough. The tongue of a domestic cat feels much like sandpaper. The tongue of a big wild cat, such as a lion or a tiger, is much rougher. The surface of the tongue is covered with small hooks, or barbs, that face backward into the throat. All cats use their tongues as grooming tools to clean and comb the fur. They also use them as tools to strip flesh off the bones of prey.
The purr
All cats—domestic and wild—can and do purr. The sound may be very loud or very soft. Kittens may begin to purr a few days after birth. In all animals, vocal sounds come from vibrations of the vocal cords, which are in the voice box in the throat. No one knows exactly how the cat uses its vocal cords to produce purring nor why no other kind of animal purrs. In addition to purring, cats make several different kinds of sounds—including meowing, chirping, hissing, yowling, and even growling.
Life cycle
A female cat may have two to three litters of young (kittens) a year. A domestic cat carries the unborn kittens inside her body for about 64 days. As the time for birth approaches, she hunts for a quiet, safe place to have her kittens. The average litter consists of four kittens but there may be only one or as many as seven. A newly born kitten weighs about 3.5 to 5 ounces (100 to 142 grams) and is about 3 inches (8 centimeters) long.
At the time of birth the kitten has no teeth, the eyes are closed, and the fur is soft and downy. The ears lie flat against the head and the tail is short and triangular. The kitten begins to get its first teeth when it is two or three weeks old. The eyes begin to open when the kitten is about 8 to 12 days old. Kittens begin to crawl out of their nest when they are about a month old. The rate of growth depends on what kind of cat it is and nutrition. Most six-month-old domestic cats weigh about 5 pounds (2.3 kilograms). Their full development takes about one year. Female cats usually become sexually mature when they are six to eight months old, and males become sexually active a few months later. A simple operation, called spaying or neutering, prevents overpopulation by removing the cat's ability to reproduce.
History
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Bombay
The first association of cats with humans may have begun toward the end of the Stone Age, some 10,000 years ago. About 4,500 years ago cats were considered sacred in Egypt. The Egyptians used the cat to hunt fish and birds as well as to destroy the rats and mice that infested the grain stocks along the Nile River. Domestic cats were also found in India, China, and Japan where they were prized as pets as well as rodent catchers. However, during the Middle Ages in Europe, the cat became an object of superstitions and was associated with witchcraft. Cats were hunted and tortured. A trace of those superstitions exists even today in the fear some have that a black cat is an unlucky omen.
Historically, dogs were the most popular pet in the United States. By the turn of the 21st century, however, the number of cats as pets outnumbered dogs.
Cats have fascinated humans for thousands of years. People have prized them as hunters and companions, worshiped them as gods, and sacrificed them as demons. They often have been used as symbols of beauty, grace, mystery, and power. Cats are members of a flesh-eating family of animals that includes the lion, tiger, jaguar, leopard, puma, cheetah, and domestic cat, or house cat. The domestic cat (species Felis catus) is a member of the larger cat family Felidae. This article discusses the domestic cat.
Form and structure
Members of the cat family are quite easy to identify. They differ widely in size, color, and markings, but they all look “catlike.” They have long, rather slender but powerfully built bodies. Domestic cats are very different from the larger cats, in coat as well as in size. Male domestic cats may reach 28 inches (71 centimeters), but 21 inches (51 centimeters) is a more usual length for females. Most female domestic cats weigh between 6 and 10 pounds (2.5 and 4.5 kilograms) while males weigh between 10 and 15 pounds (4.5 and 6.8 kilograms). The British shorthair cat may weigh up to 28 pounds (13 kilograms). Most house cats, including the Siamese and Abyssinian, are shorthaired, but the Persian has a long, thick coat. The rex, a British breed, has a curly coat. The domestic cat may be black, white, brown, gray, yellow, red, orange, stripped (tabby), mixed white, black, and yellow (tortoiseshell), or marked with patches of color (calico).
Claws and teeth
The cat is equipped to be an efficient hunter. It has strong, sharp retractile claws, which are capable of being drawn back or in, and strong, sharp teeth. The jaws of a cat are short but they, too, are extremely strong. They clamp down upon prey with enough power to crush bones. The cat's teeth are used to grab and hold prey. The sharp molars function like scissors and cut food into small pieces.
Eyes, ears, and whiskers
The cat's large and prominent eyes are placed well forward on the head. The size and position of the eyes permit as much light as possible to enter them, which ensures a large field of vision—important for hunting and night prowling. The cat's hearing also is extremely sensitive. The triangular ears can rotate rapidly to identify the source of a sound. A cat can detect many sounds that humans cannot hear. In the cat, as in humans, the inner ear contains a mechanism for maintaining body balance. It is this mechanism that lets the animal land on its feet when it falls.
A cat's whiskers serve as delicate sense organs of touch. They allow the cat to feel its way around. Four rows of stiff whiskers grow on the upper lip on each side of the nose. Small groups of whiskers also grow on other parts of the body including above each eye, on both cheeks, and on the backs of the front paws.
The tongue
A cat's tongue is rough. The tongue of a domestic cat feels much like sandpaper. The tongue of a big wild cat, such as a lion or a tiger, is much rougher. The surface of the tongue is covered with small hooks, or barbs, that face backward into the throat. All cats use their tongues as grooming tools to clean and comb the fur. They also use them as tools to strip flesh off the bones of prey.
The purr
All cats—domestic and wild—can and do purr. The sound may be very loud or very soft. Kittens may begin to purr a few days after birth. In all animals, vocal sounds come from vibrations of the vocal cords, which are in the voice box in the throat. No one knows exactly how the cat uses its vocal cords to produce purring nor why no other kind of animal purrs. In addition to purring, cats make several different kinds of sounds—including meowing, chirping, hissing, yowling, and even growling.
Life cycle
A female cat may have two to three litters of young (kittens) a year. A domestic cat carries the unborn kittens inside her body for about 64 days. As the time for birth approaches, she hunts for a quiet, safe place to have her kittens. The average litter consists of four kittens but there may be only one or as many as seven. A newly born kitten weighs about 3.5 to 5 ounces (100 to 142 grams) and is about 3 inches (8 centimeters) long.
At the time of birth the kitten has no teeth, the eyes are closed, and the fur is soft and downy. The ears lie flat against the head and the tail is short and triangular. The kitten begins to get its first teeth when it is two or three weeks old. The eyes begin to open when the kitten is about 8 to 12 days old. Kittens begin to crawl out of their nest when they are about a month old. The rate of growth depends on what kind of cat it is and nutrition. Most six-month-old domestic cats weigh about 5 pounds (2.3 kilograms). Their full development takes about one year. Female cats usually become sexually mature when they are six to eight months old, and males become sexually active a few months later. A simple operation, called spaying or neutering, prevents overpopulation by removing the cat's ability to reproduce.
History
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Bombay
The first association of cats with humans may have begun toward the end of the Stone Age, some 10,000 years ago. About 4,500 years ago cats were considered sacred in Egypt. The Egyptians used the cat to hunt fish and birds as well as to destroy the rats and mice that infested the grain stocks along the Nile River. Domestic cats were also found in India, China, and Japan where they were prized as pets as well as rodent catchers. However, during the Middle Ages in Europe, the cat became an object of superstitions and was associated with witchcraft. Cats were hunted and tortured. A trace of those superstitions exists even today in the fear some have that a black cat is an unlucky omen.
Historically, dogs were the most popular pet in the United States. By the turn of the 21st century, however, the number of cats as pets outnumbered dogs.
Scientist
07-10-2007, 10:01
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Caterpillars are the larvae, or young, of butterflies and moths. The word comes from the Latin catta pilosa, meaning “hairy cat.” Although it is easy to recognize the hairy variety, many caterpillars with bare skins are often mistaken for worms, such as the cabbageworm and armyworm.
Physical features
Body parts
The head of a caterpillar is followed by 12 or 13 segments. Like all insects, caterpillars have three pairs of permanent legs, one pair on each of the first three segments directly behind the head. These legs are usually hard and jointed. At their tips are tiny claws, but in some caterpillars these are not developed. The caterpillar also has two to five pairs of soft, thick prolegs that support the rest of its long body. These disappear when it changes into a moth or butterfly. A caterpillar has six tiny bead-like eyes on each side of the head, just above the strong upper jaws. It breathes through nine small openings on each side of its body. These are called tracheae. It also has short antennae.
Size
Caterpillars vary in size from less than an inch to a few inches. For example, the hawk moth caterpillar, one of the largest, may grow to be 4 inches (10 centimeters) long. The clothes moth caterpillar, one of the smallest, is almost never bigger than 14 inch (0.6 centimeter).
Defenses
Caterpillars are the prey of many birds and insects. To avoid attacks, they have natural protections. Some caterpillars are colored to blend into their surroundings. Others have showy dots or stripes on their bodies that make them look fierce or very large. A few give off unpleasant smells, and a small number grow poisonous hair.
Molting
A caterpillar hatches from the egg laid by a female butterfly or moth. It grows quickly and soon becomes too large for its skin. The skin splits and the caterpillar wiggles out. This process, called molting, occurs four or five times before a caterpillar turns into a butterfly or moth. Some caterpillars eat up their old skins.
Metamorphosis
The change that caterpillars undergo to turn into butterflies or moths is called metamorphosis. Some caterpillars may take only a few days to turn into butterflies or moths. Most, however, stay as caterpillars throughout the warm season. A small number may live as long as four years in the caterpillar form before they change.
Cocoon
The first step for many caterpillars is to build cocoons or shells. They spin them with threads of sticky fluid that flow from an opening in their lower lip. The fluid hardens in the air to form the covering.
Some caterpillars form bags of silk that enclose them completely. Others roll up a leaf and fasten the edges with the silk. Many hairy caterpillars pad their cocoons with their own hair. Some caterpillars do not build cocoons. Many of the moth caterpillars take shelter simply by burrowing in the ground or under a stone or fallen leaf. The butterfly caterpillars may hang from leaves or twigs by their tails. They can also spin a button of silk on a twig or leaf and dangle from it by a silk strap.
Pupa
Whether protected by a cocoon or not, the caterpillar gradually becomes ready to shed its last skin. Then the caterpillar grows a tough flexible shell or case. When this happens, the caterpillar has become a pupa. The moth pupa is usually dull brown. The butterfly pupa is sometimes called a chrysalis. It is shiny and often has brilliant colors.
Adult
Important changes happen to the pupa in the shell. Wings and other organs grow to make the caterpillar a moth or butterfly. This change to the adult stage may take anywhere from a few days to several months. Finally, the new moth or butterfly emerges from the shell and begins its new life.
Caterpillars are the larvae, or young, of butterflies and moths. The word comes from the Latin catta pilosa, meaning “hairy cat.” Although it is easy to recognize the hairy variety, many caterpillars with bare skins are often mistaken for worms, such as the cabbageworm and armyworm.
Physical features
Body parts
The head of a caterpillar is followed by 12 or 13 segments. Like all insects, caterpillars have three pairs of permanent legs, one pair on each of the first three segments directly behind the head. These legs are usually hard and jointed. At their tips are tiny claws, but in some caterpillars these are not developed. The caterpillar also has two to five pairs of soft, thick prolegs that support the rest of its long body. These disappear when it changes into a moth or butterfly. A caterpillar has six tiny bead-like eyes on each side of the head, just above the strong upper jaws. It breathes through nine small openings on each side of its body. These are called tracheae. It also has short antennae.
Size
Caterpillars vary in size from less than an inch to a few inches. For example, the hawk moth caterpillar, one of the largest, may grow to be 4 inches (10 centimeters) long. The clothes moth caterpillar, one of the smallest, is almost never bigger than 14 inch (0.6 centimeter).
Defenses
Caterpillars are the prey of many birds and insects. To avoid attacks, they have natural protections. Some caterpillars are colored to blend into their surroundings. Others have showy dots or stripes on their bodies that make them look fierce or very large. A few give off unpleasant smells, and a small number grow poisonous hair.
Molting
A caterpillar hatches from the egg laid by a female butterfly or moth. It grows quickly and soon becomes too large for its skin. The skin splits and the caterpillar wiggles out. This process, called molting, occurs four or five times before a caterpillar turns into a butterfly or moth. Some caterpillars eat up their old skins.
Metamorphosis
The change that caterpillars undergo to turn into butterflies or moths is called metamorphosis. Some caterpillars may take only a few days to turn into butterflies or moths. Most, however, stay as caterpillars throughout the warm season. A small number may live as long as four years in the caterpillar form before they change.
Cocoon
The first step for many caterpillars is to build cocoons or shells. They spin them with threads of sticky fluid that flow from an opening in their lower lip. The fluid hardens in the air to form the covering.
Some caterpillars form bags of silk that enclose them completely. Others roll up a leaf and fasten the edges with the silk. Many hairy caterpillars pad their cocoons with their own hair. Some caterpillars do not build cocoons. Many of the moth caterpillars take shelter simply by burrowing in the ground or under a stone or fallen leaf. The butterfly caterpillars may hang from leaves or twigs by their tails. They can also spin a button of silk on a twig or leaf and dangle from it by a silk strap.
Pupa
Whether protected by a cocoon or not, the caterpillar gradually becomes ready to shed its last skin. Then the caterpillar grows a tough flexible shell or case. When this happens, the caterpillar has become a pupa. The moth pupa is usually dull brown. The butterfly pupa is sometimes called a chrysalis. It is shiny and often has brilliant colors.
Adult
Important changes happen to the pupa in the shell. Wings and other organs grow to make the caterpillar a moth or butterfly. This change to the adult stage may take anywhere from a few days to several months. Finally, the new moth or butterfly emerges from the shell and begins its new life.
Scientist
07-10-2007, 10:02
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A catfish looks something like a cat because it has one or more pairs of whiskerlike feelers by its mouth. These feelers, known as barbels, are sensory organs—they help the fish to taste and feel.
Where catfish live
There are about 2,500 species, or kinds, of catfish. They are found in the freshwater bodies of all of the major continents. A few live in temperate (mild) and tropical oceans. Bullheads and channel catfish are two types of catfish common to North America.
Physical features
Catfish range greatly in size. The largest is the Danube sheatfish, or wels. This catfish may be more than 15 feet (4.5 meters) long and weigh 660 pounds (300 kilograms). Some of the smaller catfish species are popular for aquariums because they barely measure 2 inches (5 centimeters) in length.
Catfish do not have scales. All catfish are either naked or have bony plates. Many catfish have poisonous spines on their back and sides for protection from enemies.
Behavior
Catfish tend to be most active at night. They are scavengers that feed on almost any kind of animal or vegetable matter.
A female catfish can lay thousands of eggs. Some kinds of catfish carry the eggs in their broad mouths to protect them. Some others build a nest for the eggs and guard them.
Catfish and humans
Many people eat catfish. While frying the fish is perhaps the most common way it is prepared, catfish can also be cooked in other ways. Many catfish are raised in controlled environments to keep the quality and supply of catfish high. Mississippi, Arkansas, Alabama, and Louisiana are leading producers of farm-raised catfish in the United States.
Catfish are also popular to catch. People fishing in rivers may try to land a channel catfish, which can weigh more than 50 pounds (23 kilograms). Kids dangling a simple stick and worm can catch smaller catfish.
A catfish looks something like a cat because it has one or more pairs of whiskerlike feelers by its mouth. These feelers, known as barbels, are sensory organs—they help the fish to taste and feel.
Where catfish live
There are about 2,500 species, or kinds, of catfish. They are found in the freshwater bodies of all of the major continents. A few live in temperate (mild) and tropical oceans. Bullheads and channel catfish are two types of catfish common to North America.
Physical features
Catfish range greatly in size. The largest is the Danube sheatfish, or wels. This catfish may be more than 15 feet (4.5 meters) long and weigh 660 pounds (300 kilograms). Some of the smaller catfish species are popular for aquariums because they barely measure 2 inches (5 centimeters) in length.
Catfish do not have scales. All catfish are either naked or have bony plates. Many catfish have poisonous spines on their back and sides for protection from enemies.
Behavior
Catfish tend to be most active at night. They are scavengers that feed on almost any kind of animal or vegetable matter.
A female catfish can lay thousands of eggs. Some kinds of catfish carry the eggs in their broad mouths to protect them. Some others build a nest for the eggs and guard them.
Catfish and humans
Many people eat catfish. While frying the fish is perhaps the most common way it is prepared, catfish can also be cooked in other ways. Many catfish are raised in controlled environments to keep the quality and supply of catfish high. Mississippi, Arkansas, Alabama, and Louisiana are leading producers of farm-raised catfish in the United States.
Catfish are also popular to catch. People fishing in rivers may try to land a channel catfish, which can weigh more than 50 pounds (23 kilograms). Kids dangling a simple stick and worm can catch smaller catfish.
Scientist
17-10-2007, 10:40
The word cattle was once used to describe all animals raised by humans. Over time the word came to refer only to bovine farm animals that are raised for their meat, milk, or hide, as well as their close relatives, including the buffalo, bison, and yak. These animals are called bovine because they share certain features of the scientific family Bovidae. The term cattle is most often used specifically for the farm animals. Some scientists call these the true cattle.
Cattle are given different names depending on their age and ---. A male bovine, first called a bull calf, grows into a bull. The female is called a heifer calf when young and a cow in maturity. A mature male that has been operated on so that it cannot breed is known as a steer and later an ox.
Where cattle live
Cattle are found almost everywhere in the world. They are native to Europe, Asia, and Africa, but they were brought to North and South America and Australia and are now common there as well. In Asia there are both wild and domestic forms of true cattle. In the wild many cattle live in forested areas with open grassy areas nearby in which they can graze. Domestic cattle are raised by humans to be used for their milk, meat, or hide or to be used to perform heavy work. These are the animals that are most commonly thought of as cattle. In India the domestic cattle are considered holy by followers of Hinduism. It is considered a sin to kill a cow, and the animals are allowed to roam freely throughout the cities as well as the countryside.
Physical features
Depending on the breed, mature bulls weigh about 1,000–4,000 pounds (450–1,800 kilograms) and cows weigh about 800–2,400 pounds (360–1,000 kilograms). They come in a wide range of colors, including black, white, gray, yellow, brown, red, or a combination of these. They are often marked with spots and blotches. Almost all cattle have horns that are hollow.
Behavior
In the wild, cattle eat grasses and other vegetation. Cattle are ruminants, which means that they first swallow their food and then bring it up from the stomach to be chewed and swallowed again. This process is known as chewing the cud. It helps them digest difficult foods such as grasses. They do not have teeth in the front of their upper jaw. In order to eat, a bovine grabs rooted grass in its mouth. It pulls the grass free by a sideways movement of its head.
Domestic cattle are fed specific diets depending on whether they will be used as beef or dairy cattle. Beef cattle are generally heavier than dairy cattle and are fed special diets to make them fatter.
Life cycle
The life span of cattle in the wild is about 20 years. Cows give birth to one or two young about nine months after mating. At birth, a calf weighs about 80 pounds (36 kilograms). Beef calves are weaned, or taken off their mother's milk, at 6 to 7 months of age. At this time they weigh from 350 to 650 pounds (160 to 300 kilograms). Most fattened beef cattle are taken to market between 15 to 24 months of age, when they weigh between 1,000 and 1,400 pounds (450 and 630 kilograms).
Breeds
All modern European domestic cattle are thought to have descended from a form, known as the aurochs, that lived in Asia and Europe in ancient times. Beginning about 8,000 years ago people began to domesticate the animal. At first they used all cattle for all purposes. Eventually, however, they began to develop separate breeds that had unique features. Modern cattle in the United States and Europe can be categorized into two main varieties, dairy and beef, though some cattle continue to serve more than one purpose. Each of these categories has a number of breeds.
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Hereford bull
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Holstein-Friesian cow
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Brahman bull
The most popular dairy cattle in the United States include the Holstein-Friesian, Brown Swiss, Jersey, and Guernsey breeds. Of the cattle raised for beef, the Angus, Shorthorn (or Durham), Hereford, and Brahman are among the most common breeds. The Brahman was originally produced by mating the Indian cattle known as the zebu with certain domestic breeds. The Brahman is popular in the southern United States because it endures heat and resists disease and insect bites better than other breeds. The Brahman is characterized by a pronounced hump over the shoulder and neck, horns that usually curve up and back, and drooping ears.
Cattle and humans
Cattle are very important to the economies of many countries as well as to small farmers throughout the world. Millions of beef and dairy cattle throughout the world produce meat, milk, cheese, butter, and other products. Their skin is made into leather goods. In addition, they help plow farmers' fields and haul heavy loads.
Because of their importance, cattle are monitored closely to make sure they do not have any diseases that could affect them or be passed along to humans. Tuberculosis, a bacterial disease in cattle, is harmful to humans. It is spread through infected milk and milk products. However, the bacteria can be killed by pasteurization, which is a heat treatment process that kills disease-causing microorganisms. Foot-and-mouth disease causes sores in the mouth and between the toes of cattle. Texas fever is caused by a microscopic parasite carried by ticks. The parasite destroys the blood cells of the cattle.
Bovine Spongiform Encephalopathy (BSE), or mad cow disease, was first diagnosed in British cattle in about 1986. BSE attacks the nerve cells of the cattle's brain. Because there may be a link between BSE and a similar fatal brain disease in humans, known as Creutzfeldt-Jakob disease (CJD), cattle diagnosed with BSE are destroyed.
Cattle are given different names depending on their age and ---. A male bovine, first called a bull calf, grows into a bull. The female is called a heifer calf when young and a cow in maturity. A mature male that has been operated on so that it cannot breed is known as a steer and later an ox.
Where cattle live
Cattle are found almost everywhere in the world. They are native to Europe, Asia, and Africa, but they were brought to North and South America and Australia and are now common there as well. In Asia there are both wild and domestic forms of true cattle. In the wild many cattle live in forested areas with open grassy areas nearby in which they can graze. Domestic cattle are raised by humans to be used for their milk, meat, or hide or to be used to perform heavy work. These are the animals that are most commonly thought of as cattle. In India the domestic cattle are considered holy by followers of Hinduism. It is considered a sin to kill a cow, and the animals are allowed to roam freely throughout the cities as well as the countryside.
Physical features
Depending on the breed, mature bulls weigh about 1,000–4,000 pounds (450–1,800 kilograms) and cows weigh about 800–2,400 pounds (360–1,000 kilograms). They come in a wide range of colors, including black, white, gray, yellow, brown, red, or a combination of these. They are often marked with spots and blotches. Almost all cattle have horns that are hollow.
Behavior
In the wild, cattle eat grasses and other vegetation. Cattle are ruminants, which means that they first swallow their food and then bring it up from the stomach to be chewed and swallowed again. This process is known as chewing the cud. It helps them digest difficult foods such as grasses. They do not have teeth in the front of their upper jaw. In order to eat, a bovine grabs rooted grass in its mouth. It pulls the grass free by a sideways movement of its head.
Domestic cattle are fed specific diets depending on whether they will be used as beef or dairy cattle. Beef cattle are generally heavier than dairy cattle and are fed special diets to make them fatter.
Life cycle
The life span of cattle in the wild is about 20 years. Cows give birth to one or two young about nine months after mating. At birth, a calf weighs about 80 pounds (36 kilograms). Beef calves are weaned, or taken off their mother's milk, at 6 to 7 months of age. At this time they weigh from 350 to 650 pounds (160 to 300 kilograms). Most fattened beef cattle are taken to market between 15 to 24 months of age, when they weigh between 1,000 and 1,400 pounds (450 and 630 kilograms).
Breeds
All modern European domestic cattle are thought to have descended from a form, known as the aurochs, that lived in Asia and Europe in ancient times. Beginning about 8,000 years ago people began to domesticate the animal. At first they used all cattle for all purposes. Eventually, however, they began to develop separate breeds that had unique features. Modern cattle in the United States and Europe can be categorized into two main varieties, dairy and beef, though some cattle continue to serve more than one purpose. Each of these categories has a number of breeds.
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Hereford bull
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Holstein-Friesian cow
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Brahman bull
The most popular dairy cattle in the United States include the Holstein-Friesian, Brown Swiss, Jersey, and Guernsey breeds. Of the cattle raised for beef, the Angus, Shorthorn (or Durham), Hereford, and Brahman are among the most common breeds. The Brahman was originally produced by mating the Indian cattle known as the zebu with certain domestic breeds. The Brahman is popular in the southern United States because it endures heat and resists disease and insect bites better than other breeds. The Brahman is characterized by a pronounced hump over the shoulder and neck, horns that usually curve up and back, and drooping ears.
Cattle and humans
Cattle are very important to the economies of many countries as well as to small farmers throughout the world. Millions of beef and dairy cattle throughout the world produce meat, milk, cheese, butter, and other products. Their skin is made into leather goods. In addition, they help plow farmers' fields and haul heavy loads.
Because of their importance, cattle are monitored closely to make sure they do not have any diseases that could affect them or be passed along to humans. Tuberculosis, a bacterial disease in cattle, is harmful to humans. It is spread through infected milk and milk products. However, the bacteria can be killed by pasteurization, which is a heat treatment process that kills disease-causing microorganisms. Foot-and-mouth disease causes sores in the mouth and between the toes of cattle. Texas fever is caused by a microscopic parasite carried by ticks. The parasite destroys the blood cells of the cattle.
Bovine Spongiform Encephalopathy (BSE), or mad cow disease, was first diagnosed in British cattle in about 1986. BSE attacks the nerve cells of the cattle's brain. Because there may be a link between BSE and a similar fatal brain disease in humans, known as Creutzfeldt-Jakob disease (CJD), cattle diagnosed with BSE are destroyed.
Scientist
17-10-2007, 10:42
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The large, meat-eating dinosaur Ceratosaurus can be recognized by the large horn on its snout. This feature earned it the name Ceratosaurus, which means “horned lizard.” Although it was smaller, Ceratosaurus looked very much like its rival, Allosaurus. Ceratosaurus belongs to the group of meat-eating dinosaurs known as theropods.
Where and when Ceratosaurus lived
Ceratosaurus lived about 159 to 144 million years ago, during the period of the Earth's history known as the Jurassic. Remains of Ceratosaurus have been found in Africa and in North America in Colorado, Utah, and Wyoming. Like Allosaurus, Ceratosaurus lived in the fern savannas and wooded floodplains that had thick vegetation, where its plant-eating prey could be found.
Physical features
Ceratosaurus was a fierce-looking dinosaur that stood and walked on its two back legs. It could reach a length of more than 20 feet (6 meters) and stood about 6 12 feet (2 meters) tall. Ceratosaurus weighed up to 2 tons. In addition to the bony horn on its snout, Ceratosaurus also had a bony ridge above each eye. It had a short, thick neck. Its head was large but light for its size and had strong jaws and long, razor-sharp teeth. Ceratosaurus also had a row of bony plates that ran along its back, from its neck to the end of its long, thick tail. These bony plates looked like the small spiny ridges that run down the backs of modern iguanas. Ceratosaurus had short arms, but unlike other theropods, it had four long-clawed fingers on its front feet, instead of three. It also had three clawed toes on its back feet.
Behavior
Ceratosaurus was the sprinter of the dinosaur world. Using its powerful back legs, it could take off and run at high speeds. This ability allowed it to outrun enemies and to capture prey with a sudden burst of speed. Scientists believe that Ceratosaurus was also a scavenger that fed on the dead bodies of other dinosaurs. Fossil findings show that Ceratosaurus probably hunted alone, rather than in packs. Some scientists believe that male Ceratosaurus, during the breeding season, may have used the horns on their snouts in combat with one another. Other scientists argue, however, that because it was so lightweight, the horn may have been used simply for show. Males may have bobbed their heads up and down to show off their horn, much in the way some modern reptiles do. Fossil findings show that male Ceratosaurus were larger and stronger than the females. Ceratosaurus reproduced by laying eggs.
The large, meat-eating dinosaur Ceratosaurus can be recognized by the large horn on its snout. This feature earned it the name Ceratosaurus, which means “horned lizard.” Although it was smaller, Ceratosaurus looked very much like its rival, Allosaurus. Ceratosaurus belongs to the group of meat-eating dinosaurs known as theropods.
Where and when Ceratosaurus lived
Ceratosaurus lived about 159 to 144 million years ago, during the period of the Earth's history known as the Jurassic. Remains of Ceratosaurus have been found in Africa and in North America in Colorado, Utah, and Wyoming. Like Allosaurus, Ceratosaurus lived in the fern savannas and wooded floodplains that had thick vegetation, where its plant-eating prey could be found.
Physical features
Ceratosaurus was a fierce-looking dinosaur that stood and walked on its two back legs. It could reach a length of more than 20 feet (6 meters) and stood about 6 12 feet (2 meters) tall. Ceratosaurus weighed up to 2 tons. In addition to the bony horn on its snout, Ceratosaurus also had a bony ridge above each eye. It had a short, thick neck. Its head was large but light for its size and had strong jaws and long, razor-sharp teeth. Ceratosaurus also had a row of bony plates that ran along its back, from its neck to the end of its long, thick tail. These bony plates looked like the small spiny ridges that run down the backs of modern iguanas. Ceratosaurus had short arms, but unlike other theropods, it had four long-clawed fingers on its front feet, instead of three. It also had three clawed toes on its back feet.
Behavior
Ceratosaurus was the sprinter of the dinosaur world. Using its powerful back legs, it could take off and run at high speeds. This ability allowed it to outrun enemies and to capture prey with a sudden burst of speed. Scientists believe that Ceratosaurus was also a scavenger that fed on the dead bodies of other dinosaurs. Fossil findings show that Ceratosaurus probably hunted alone, rather than in packs. Some scientists believe that male Ceratosaurus, during the breeding season, may have used the horns on their snouts in combat with one another. Other scientists argue, however, that because it was so lightweight, the horn may have been used simply for show. Males may have bobbed their heads up and down to show off their horn, much in the way some modern reptiles do. Fossil findings show that male Ceratosaurus were larger and stronger than the females. Ceratosaurus reproduced by laying eggs.
Scientist
17-10-2007, 10:45
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Over short distances, no animal on Earth can outrun the cheetah. This large, spotted cat can sprint at more than 60 miles (100 kilometers) per hour, and it requires only a few seconds to reach top speed. The scientific name of the cheetah is Acinonyx jubatus.
Where cheetahs live
Cheetahs can live in a variety of places, but they especially like open grasslands. They use hills or low tree branches as lookout points. Cheetahs were once found throughout Africa except for in the rain forests and part of the Sahara. Now, however, African cheetahs are found only in scattered parts of central, eastern, and southern Africa. Cheetahs also used to roam over much of western and southern Asia, from the Middle East to India. Today Asian cheetahs are limited to a small number in Iran and the surrounding area.
Physical features
In the Hindi language of India, cheetah means “spotted one.” The name refers to the small black spots on the cheetah's sandy yellow fur. In one rare variety, the king cheetah, some of the spots run together to create a blotched or striped pattern. The only part of a cheetah without spots is the white belly. The cheetah's tail is marked with dark rings. Because of its spots, the cheetah is sometimes confused with another cat, the leopard. One difference between the two is that the cheetah's spots are not clustered in groups like those of the leopard. Another unique feature of the cheetah is the black lines running from the eyes to the corners of the mouth. These are sometimes called tear marks.
The cheetah measures about 55 inches (140 centimeters) long from head to tail. The tail adds another 30 inches (76 centimeters) to the length. The animal stands about 31 inches (80 centimeters) tall at the shoulder. It is a slender cat that weighs about 110–130 pounds (50–60 kilograms). Males tend to be larger than females.
A cheetah's body is built for speed. Several special traits, or adaptations, help the cheetah while sprinting. Long legs allow the cheetah to take big strides. Ridged footpads, along with specially adapted claws, help it to grip the ground. The cheetah is the only kind of cat that cannot pull its claws completely back, meaning that its claws, like those of a dog, are always exposed. The animal's large heart and lungs deliver the oxygen needed for sprinting.
Behavior
Cheetahs live alone or in small groups. The groups generally consist of either a female with her young or a few males. A female lives alone when it is not raising cubs. Cheetah groups generally stay out of each other's territory.
Although most cats are active at night, cheetahs usually hunt in the morning or late afternoon. Their method of hunting is also unique. Most cats pounce on a prey animal after either lying in wait for it to approach or sneaking up on it. The cheetah, however, uses its speed to chase down its prey, which is often a small antelope. After first creeping up on an animal, a cheetah sprints at it from a few hundred feet away. The cheetah can overtake even the fastest prey, but it can keep up the chase for only about 1,300–1,600 feet (400–490 meters) before tiring. Often the prey is able to escape. When the cheetah does catch its prey, it trips the animal with a blow to its back legs. The cheetah kills the prey by biting into its throat.
A cheetah that has just made a kill is often exhausted and weak. Lions or other rival predators sometimes take advantage of this period of weakness by stealing the cheetah's catch.
Life cycle
Male and female cheetahs come together only to breed. About 90 to 95 days after mating, a female cheetah usually gives birth to about two to four cubs. The newborn cubs are blind and helpless. Within about 12 days, however, they open their eyes and begin to walk. For the first few months of life a baby cheetah has a dark-spotted coat with long, blue-gray hair on the head, neck, and back. The coat changes as the cub grows.
Many cheetah cubs fall victim to other predators such as lions and hyenas. The survivors stay with their mother for 15–17 months while they learn to hunt. After about two years the young cheetahs are ready to breed. Some cheetahs in zoos have reached the age of 19, but most do not live that long.
Relationship with humans
In ancient times people learned that cheetahs could be tamed and trained as hunting companions. The ancient Egyptians used cheetahs in this way, and later the tradition passed to the rulers of India and Europe. For this reason cheetahs are sometimes called hunting leopards. The hunters released a cheetah in sight of a prey animal. If the cheetah's chase was successful, the hunters gave it part of the catch and took the rest for themselves. All cheetahs used for this purpose were taken from the wild, causing a steady decline in cheetah populations. Adding to the problem was the hunting of cheetahs themselves for their fur. Eventually cheetahs disappeared from India and other places.
Today cheetahs continue to face a number of threats to their survival. Farmers trap or kill cheetahs because the animals sometimes attack livestock. Another danger is the expansion of human settlements onto the land where cheetahs live. This reduces the living space of both the cheetah and the animals on which it preys. Conservation groups are working with farmers to come up with new ways to deal with the animals. They have also taken steps to preserve the cheetah's remaining habitat.
Over short distances, no animal on Earth can outrun the cheetah. This large, spotted cat can sprint at more than 60 miles (100 kilometers) per hour, and it requires only a few seconds to reach top speed. The scientific name of the cheetah is Acinonyx jubatus.
Where cheetahs live
Cheetahs can live in a variety of places, but they especially like open grasslands. They use hills or low tree branches as lookout points. Cheetahs were once found throughout Africa except for in the rain forests and part of the Sahara. Now, however, African cheetahs are found only in scattered parts of central, eastern, and southern Africa. Cheetahs also used to roam over much of western and southern Asia, from the Middle East to India. Today Asian cheetahs are limited to a small number in Iran and the surrounding area.
Physical features
In the Hindi language of India, cheetah means “spotted one.” The name refers to the small black spots on the cheetah's sandy yellow fur. In one rare variety, the king cheetah, some of the spots run together to create a blotched or striped pattern. The only part of a cheetah without spots is the white belly. The cheetah's tail is marked with dark rings. Because of its spots, the cheetah is sometimes confused with another cat, the leopard. One difference between the two is that the cheetah's spots are not clustered in groups like those of the leopard. Another unique feature of the cheetah is the black lines running from the eyes to the corners of the mouth. These are sometimes called tear marks.
The cheetah measures about 55 inches (140 centimeters) long from head to tail. The tail adds another 30 inches (76 centimeters) to the length. The animal stands about 31 inches (80 centimeters) tall at the shoulder. It is a slender cat that weighs about 110–130 pounds (50–60 kilograms). Males tend to be larger than females.
A cheetah's body is built for speed. Several special traits, or adaptations, help the cheetah while sprinting. Long legs allow the cheetah to take big strides. Ridged footpads, along with specially adapted claws, help it to grip the ground. The cheetah is the only kind of cat that cannot pull its claws completely back, meaning that its claws, like those of a dog, are always exposed. The animal's large heart and lungs deliver the oxygen needed for sprinting.
Behavior
Cheetahs live alone or in small groups. The groups generally consist of either a female with her young or a few males. A female lives alone when it is not raising cubs. Cheetah groups generally stay out of each other's territory.
Although most cats are active at night, cheetahs usually hunt in the morning or late afternoon. Their method of hunting is also unique. Most cats pounce on a prey animal after either lying in wait for it to approach or sneaking up on it. The cheetah, however, uses its speed to chase down its prey, which is often a small antelope. After first creeping up on an animal, a cheetah sprints at it from a few hundred feet away. The cheetah can overtake even the fastest prey, but it can keep up the chase for only about 1,300–1,600 feet (400–490 meters) before tiring. Often the prey is able to escape. When the cheetah does catch its prey, it trips the animal with a blow to its back legs. The cheetah kills the prey by biting into its throat.
A cheetah that has just made a kill is often exhausted and weak. Lions or other rival predators sometimes take advantage of this period of weakness by stealing the cheetah's catch.
Life cycle
Male and female cheetahs come together only to breed. About 90 to 95 days after mating, a female cheetah usually gives birth to about two to four cubs. The newborn cubs are blind and helpless. Within about 12 days, however, they open their eyes and begin to walk. For the first few months of life a baby cheetah has a dark-spotted coat with long, blue-gray hair on the head, neck, and back. The coat changes as the cub grows.
Many cheetah cubs fall victim to other predators such as lions and hyenas. The survivors stay with their mother for 15–17 months while they learn to hunt. After about two years the young cheetahs are ready to breed. Some cheetahs in zoos have reached the age of 19, but most do not live that long.
Relationship with humans
In ancient times people learned that cheetahs could be tamed and trained as hunting companions. The ancient Egyptians used cheetahs in this way, and later the tradition passed to the rulers of India and Europe. For this reason cheetahs are sometimes called hunting leopards. The hunters released a cheetah in sight of a prey animal. If the cheetah's chase was successful, the hunters gave it part of the catch and took the rest for themselves. All cheetahs used for this purpose were taken from the wild, causing a steady decline in cheetah populations. Adding to the problem was the hunting of cheetahs themselves for their fur. Eventually cheetahs disappeared from India and other places.
Today cheetahs continue to face a number of threats to their survival. Farmers trap or kill cheetahs because the animals sometimes attack livestock. Another danger is the expansion of human settlements onto the land where cheetahs live. This reduces the living space of both the cheetah and the animals on which it preys. Conservation groups are working with farmers to come up with new ways to deal with the animals. They have also taken steps to preserve the cheetah's remaining habitat.
Scientist
17-10-2007, 10:47
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Thought to be the closest living relative to humans, the chimpanzee is a type of African great ape. Chimpanzees are very smart, social, and active animals. Their scientific name is Pan troglodytes.
Where chimpanzees live
Chimpanzees are found in Africa in the countries that lie along the equator. They live mostly in tropical rain forests. They sometimes live in drier woodland savannas as well.
Physical features
Individual chimpanzees vary in size and appearance. They usually stand about 3 to 512 feet (1 to 1.7 meters) tall and weigh about 57 to 154 pounds (26 to 70 kilograms). Males are usually larger than females. A chimpanzee's arms are longer than its legs, reaching just below the knees when the animal stands.
Chimpanzees have a coat of brown or black hair. Their face, ears, hands, and feet are bare. Their skin color is black, though it may be pink or brown in younger animals. Their head is covered with just a little bit of hair, which both males and females lose as they grow older. The top of the head is rounded. Their ears stick out, and their lips protrude. Their jaw projects out beyond the upper part of the face.
Behavior
Chimpanzees spend time both in trees and on the ground. In trees, they use both their hands and their feet to move, or they swing by their arms from branch to branch. If they must go long distances, they usually travel on the ground. Chimpanzees can walk upright, but they more often lean on the knuckles of their hands and walk on all fours. Chimpanzees are active during the day. At night they usually sleep in the trees in nests that they make out of branches and leaves.
Chimpanzees do not usually eat meat. Their diet is made up mostly of fruits, berries, leaves, and seeds. They sometimes eat termites and ants and occasionally hunt and eat young baboons and bush pigs.
No animals besides humans use tools as well as chimpanzees. Chimpanzees poke twigs, grass, or other objects into ant and termite nests, pull out the tool, and eat the insects that cling to it. They also use leaves to soak up drinking water and to clean themselves. Young chimpanzees probably learn how to use tools by watching and imitating adults.
Chimpanzees are very social animals that live in groups known as communities. Each community has a male leader and 15 to 120 members, usually divided into smaller groups. Those groups continually change, and relationships between them are generally friendly. Members of a community are free to come and go as they wish. Different communities, however, often do not get along with each other. Chimpanzees of one community sometimes attack and fight chimpanzees of another community.
Adult chimpanzees in the same community regularly groom each other's fur. That behavior helps them to bond with one another. Chimpanzees communicate by facial expressions, gestures, and many different sounds, including screams, hoots, grunts, and roars.
Life cycle
Mating can happen at any time of year. Female chimpanzees give birth to a single young after a pregnancy of about eight months. A newborn weighs about 4 pounds (1.8 kilograms), is almost helpless, and clings to the fur of the mother's belly when she moves. From about 6 months to 2 years, the youngster rides on the mother's back. Chimpanzees can live up to about 50 years.
Chimpanzees and humans
The number of chimpanzees in the wild has greatly fallen, mainly because of human behavior. Humans hunt chimpanzees, destroy their habitat through logging and farming, and capture them for use in zoos and research laboratories. Chimpanzees are now considered an endangered species, a type of animal that is at risk of dying out.
Thought to be the closest living relative to humans, the chimpanzee is a type of African great ape. Chimpanzees are very smart, social, and active animals. Their scientific name is Pan troglodytes.
Where chimpanzees live
Chimpanzees are found in Africa in the countries that lie along the equator. They live mostly in tropical rain forests. They sometimes live in drier woodland savannas as well.
Physical features
Individual chimpanzees vary in size and appearance. They usually stand about 3 to 512 feet (1 to 1.7 meters) tall and weigh about 57 to 154 pounds (26 to 70 kilograms). Males are usually larger than females. A chimpanzee's arms are longer than its legs, reaching just below the knees when the animal stands.
Chimpanzees have a coat of brown or black hair. Their face, ears, hands, and feet are bare. Their skin color is black, though it may be pink or brown in younger animals. Their head is covered with just a little bit of hair, which both males and females lose as they grow older. The top of the head is rounded. Their ears stick out, and their lips protrude. Their jaw projects out beyond the upper part of the face.
Behavior
Chimpanzees spend time both in trees and on the ground. In trees, they use both their hands and their feet to move, or they swing by their arms from branch to branch. If they must go long distances, they usually travel on the ground. Chimpanzees can walk upright, but they more often lean on the knuckles of their hands and walk on all fours. Chimpanzees are active during the day. At night they usually sleep in the trees in nests that they make out of branches and leaves.
Chimpanzees do not usually eat meat. Their diet is made up mostly of fruits, berries, leaves, and seeds. They sometimes eat termites and ants and occasionally hunt and eat young baboons and bush pigs.
No animals besides humans use tools as well as chimpanzees. Chimpanzees poke twigs, grass, or other objects into ant and termite nests, pull out the tool, and eat the insects that cling to it. They also use leaves to soak up drinking water and to clean themselves. Young chimpanzees probably learn how to use tools by watching and imitating adults.
Chimpanzees are very social animals that live in groups known as communities. Each community has a male leader and 15 to 120 members, usually divided into smaller groups. Those groups continually change, and relationships between them are generally friendly. Members of a community are free to come and go as they wish. Different communities, however, often do not get along with each other. Chimpanzees of one community sometimes attack and fight chimpanzees of another community.
Adult chimpanzees in the same community regularly groom each other's fur. That behavior helps them to bond with one another. Chimpanzees communicate by facial expressions, gestures, and many different sounds, including screams, hoots, grunts, and roars.
Life cycle
Mating can happen at any time of year. Female chimpanzees give birth to a single young after a pregnancy of about eight months. A newborn weighs about 4 pounds (1.8 kilograms), is almost helpless, and clings to the fur of the mother's belly when she moves. From about 6 months to 2 years, the youngster rides on the mother's back. Chimpanzees can live up to about 50 years.
Chimpanzees and humans
The number of chimpanzees in the wild has greatly fallen, mainly because of human behavior. Humans hunt chimpanzees, destroy their habitat through logging and farming, and capture them for use in zoos and research laboratories. Chimpanzees are now considered an endangered species, a type of animal that is at risk of dying out.
Scientist
17-10-2007, 10:49
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Closely related to squirrels, chipmunks can be told apart by their small size, striped backs, large cheek pouches, and habit of staying on the ground. Chipmunks are burrowing rodents. They keep nuts and other food stored in their burrows for winter.
Where chipmunks live
Chipmunks may be found in a wide range of habitats, including woodlands, mountains, and plains. All but one species, or type, are North American. The eastern chipmunk ranges from Canada southward to Georgia and westward to the Great Plains. Many different kinds of western chipmunks live in western North America. The one species that lives outside of North America is the Asiatic chipmunk, which is found in northern Asia and parts of eastern Europe.
Physical features
All chipmunks are quite small. The eastern chipmunk is 512 to 712 inches (14 to 19 centimeters) long. Its bushy tail is more than half as long as its body. It weighs only about 212 to 5 ounces (71 to 142 grams). The western and Asiatic chipmunks are even smaller.
Chipmunks can be identified by their colors and stripes. The eastern chipmunk is reddish brown with five dark stripes on its back. Between the dark stripes are two brown and two white stripes. The western and Asiatic chipmunks come in various colors, but many are yellowish. Like the eastern chipmunk, they have five dark stripes. However, all four areas between the stripes are whitish.
Behavior
Although chipmunks prefer to live on the ground, they are good tree climbers and can also swim. They make a shrill chattering sound. They like to eat nuts, seeds, wild fruits, and berries. They have inner cheek pouches that they can stuff with food. They carry the food home and store it for the winter.
Each chipmunk has its own burrow in the middle of its own territory. The burrow is dug under rocks or tree roots or logs. It contains at least two chambers—one a storeroom for nuts and the other a leaf-lined nest. Chipmunks sleep during most of the winter, but not deeply enough to be considered true hibernators. From time to time they get up to eat.
Life cycle
Mating usually occurs in late winter or early spring. One month later, the female chipmunk gives birth to four or five young. In warmer regions there may be two mating seasons in the same year. After about one month, the young first leave the nest. After about two months, they go out on their own, and after three months they are fully grown.
Closely related to squirrels, chipmunks can be told apart by their small size, striped backs, large cheek pouches, and habit of staying on the ground. Chipmunks are burrowing rodents. They keep nuts and other food stored in their burrows for winter.
Where chipmunks live
Chipmunks may be found in a wide range of habitats, including woodlands, mountains, and plains. All but one species, or type, are North American. The eastern chipmunk ranges from Canada southward to Georgia and westward to the Great Plains. Many different kinds of western chipmunks live in western North America. The one species that lives outside of North America is the Asiatic chipmunk, which is found in northern Asia and parts of eastern Europe.
Physical features
All chipmunks are quite small. The eastern chipmunk is 512 to 712 inches (14 to 19 centimeters) long. Its bushy tail is more than half as long as its body. It weighs only about 212 to 5 ounces (71 to 142 grams). The western and Asiatic chipmunks are even smaller.
Chipmunks can be identified by their colors and stripes. The eastern chipmunk is reddish brown with five dark stripes on its back. Between the dark stripes are two brown and two white stripes. The western and Asiatic chipmunks come in various colors, but many are yellowish. Like the eastern chipmunk, they have five dark stripes. However, all four areas between the stripes are whitish.
Behavior
Although chipmunks prefer to live on the ground, they are good tree climbers and can also swim. They make a shrill chattering sound. They like to eat nuts, seeds, wild fruits, and berries. They have inner cheek pouches that they can stuff with food. They carry the food home and store it for the winter.
Each chipmunk has its own burrow in the middle of its own territory. The burrow is dug under rocks or tree roots or logs. It contains at least two chambers—one a storeroom for nuts and the other a leaf-lined nest. Chipmunks sleep during most of the winter, but not deeply enough to be considered true hibernators. From time to time they get up to eat.
Life cycle
Mating usually occurs in late winter or early spring. One month later, the female chipmunk gives birth to four or five young. In warmer regions there may be two mating seasons in the same year. After about one month, the young first leave the nest. After about two months, they go out on their own, and after three months they are fully grown.
Scientist
05-12-2007, 11:50
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ] are deadly, poisonous snakes known for their ability to flatten their necks into the shape of a hood when threatened. Snake charmers often use cobras to make their act seem dangerous and exciting. Cobras can inject their enemies with a powerful, paralyzing venom. Despite their fierce reputation, however, most cobras would rather retreat instead of confronting an enemy.
Where cobras live
Cobras live in warm regions throughout Asia, Australia, and Africa. Some dwell in grasslands, forests, or deserts. Others live in trees or along the shores of lakes.
Physical features
The bodies of cobras are medium to large in size and usually a single color or spotted. The king cobra of Asia is the world's longest poisonous snake. It can reach a length of about 18 feet (5.5 meters).
All types of cobras are able to lift up the skin behind their head so that it looks like a hood. When the cobra is threatened, it extends its long, flexible back ribs sideways and forward. This stretches the skin to create the hood. The size of the hood varies with the type of snake. Some cobras have distinct markings on their hoods.
All cobras also have short, hollow front fangs that deliver venom to their prey. Most cobras have holes at the bottom of their fangs, but the African ringhals and other spitting cobras have small holes at the front. They can accurately squirt a stream of venom at high speed into an intruder's eyes. Some large cobras can spit venom a distance of 7 feet (2 meters) or more. The venom does not harm the skin, but it can cause intense pain and permanent blindness in the eyes if they are not promptly treated. The snake spits the venom to distract an intruder while it retreats. Such snakes also inject venom into prey through a bite.
Behavior
Cobras hunt in the evening and at night, often hiding in animal burrows and termite mounds. Their prey includes mammals, birds, snakes, lizards, frogs, and even fish. The small mammal known as the mongoose is an enemy of the cobra. It attacks the cobra quickly from above to avoid the snake's strike.
A cobra takes on a fierce posture when threatened. It rears its head up off the ground to almost one-third of its body length and spreads its hood. Some cobras add a hiss to this posture, and the king cobra gives a loud growl. It is from this position that the cobra strikes in self-defense.
Life cycle
Females lay up to several dozen eggs and hide them in leaf piles and other warm, moist places. King cobras loop their bodies to scoop vegetation and build a nest. Some cobras, including king cobras, guard their eggs until they hatch.
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ] are deadly, poisonous snakes known for their ability to flatten their necks into the shape of a hood when threatened. Snake charmers often use cobras to make their act seem dangerous and exciting. Cobras can inject their enemies with a powerful, paralyzing venom. Despite their fierce reputation, however, most cobras would rather retreat instead of confronting an enemy.
Where cobras live
Cobras live in warm regions throughout Asia, Australia, and Africa. Some dwell in grasslands, forests, or deserts. Others live in trees or along the shores of lakes.
Physical features
The bodies of cobras are medium to large in size and usually a single color or spotted. The king cobra of Asia is the world's longest poisonous snake. It can reach a length of about 18 feet (5.5 meters).
All types of cobras are able to lift up the skin behind their head so that it looks like a hood. When the cobra is threatened, it extends its long, flexible back ribs sideways and forward. This stretches the skin to create the hood. The size of the hood varies with the type of snake. Some cobras have distinct markings on their hoods.
All cobras also have short, hollow front fangs that deliver venom to their prey. Most cobras have holes at the bottom of their fangs, but the African ringhals and other spitting cobras have small holes at the front. They can accurately squirt a stream of venom at high speed into an intruder's eyes. Some large cobras can spit venom a distance of 7 feet (2 meters) or more. The venom does not harm the skin, but it can cause intense pain and permanent blindness in the eyes if they are not promptly treated. The snake spits the venom to distract an intruder while it retreats. Such snakes also inject venom into prey through a bite.
Behavior
Cobras hunt in the evening and at night, often hiding in animal burrows and termite mounds. Their prey includes mammals, birds, snakes, lizards, frogs, and even fish. The small mammal known as the mongoose is an enemy of the cobra. It attacks the cobra quickly from above to avoid the snake's strike.
A cobra takes on a fierce posture when threatened. It rears its head up off the ground to almost one-third of its body length and spreads its hood. Some cobras add a hiss to this posture, and the king cobra gives a loud growl. It is from this position that the cobra strikes in self-defense.
Life cycle
Females lay up to several dozen eggs and hide them in leaf piles and other warm, moist places. King cobras loop their bodies to scoop vegetation and build a nest. Some cobras, including king cobras, guard their eggs until they hatch.
Scientist
05-12-2007, 12:05
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
Corals are small marine animals that stay in one place throughout their adult lives. These animals produce a hard skeleton made of calcium carbonate, or limestone. The skeletal material, which outlives the animal, is also called coral. Corals can be very colorful underwater, but most types fade when they die or are removed from the water. The red coral, found in the Mediterranean Sea and in the coastal waters of Japan, does not lose its color when removed from the water. Because of this quality it has been used in jewelry for centuries.
Where corals live
Corals live in all the oceans of the world. Many types grow in colonies that continue to enlarge year after year. Other types are solitary, meaning that they live alone. Several different types of corals can together form enormous colonies. These colonies are called coral reefs, coral islands, and coral atolls. The largest reefs are found in the warmer portions of the Pacific and Indian oceans. However, coral reefs are also found in the Caribbean and in the Gulf of Mexico as far north as southern Florida.
Coral reefs are composed of different types of corals. The reefs create underwater habitats that are essential for many species of marine organisms. Certain kinds of fish spend their life among the corals, using them as a refuge from predators. The largest coral reef in the world, the Great Barrier Reef off the coast of Australia, is more than 1,250 miles (2,000 kilometers) long. More than 350 species of coral have been found in the Great Barrier Reef.
Physical characteristics
Coral reefs have different shapes and patterns because of the growth pattern of the millions of tiny individual animals that make up a colony. Reefs can look like beautiful underwater gardens. Some corals resemble the tendrils of plants, while some may look like leaves. The brain coral is nearly spherical and has grooves that make it look like a human brain. Corals with flat, fan-shaped structures that spread out from a narrower base are called sea fans. The organ-pipe corals, which are found in the tropical oceans of the Indo-Pacific, are typically long rigid tubes.
The corals' skeletons, external or internal, have a stonelike, horny, or leathery texture. The body of a coral animal consists of a polyp—a hollow, cylindrical structure attached at its lower end to some surface. The largest of the solitary polyps grows to a diameter of about 10 inches (25 centimeters). The polyps of the corals that form reefs range from 0.04 to 1.2 inches (0.1 to 3 centimeters) in diameter.
Life cycle
Corals reproduce in two different ways. In one process, fertilized eggs develop into tiny, swimming organisms called planulae. Planulae eventually settle on the bottom of the ocean, on a rock or on another coral, and develop into polyps. Each polyp builds a limestone skeleton attached to the surface on which the polyp has landed. After the coral establishes itself, the upper part of the body becomes dome-shaped and develops a stomach and mouth.
Reproduction also can occur by budding. A bud develops the body of a polyp and remains attached there. A colony develops by the constant addition and growth of new buds. As new polyps develop, the older, underlying polyps die, leaving behind their skeletons. In some kinds of coral the buds may break away to become separate individuals. Vast coral colonies are built by budding, with the animals connected by their extensive skeletal network.
Food habits
Small marine organisms are the major food of corals. At the free end of the polyp is a mouth surrounded by tentacles. The tentacles gather food from the surrounding waters. Corals are also armed with specialized stinging structures, called nematocysts, that paralyze their prey. Nutrients are passed from individual corals on the outside of a colony to those on the inside.
Ecological issues
By the 1990s coral reefs off the coasts of more than 20 countries were being destroyed for a number of reasons. Rising water temperature is said to cause bleaching, which the corals cannot withstand. Oil spills and chemical pollution also are a major threat to corals. Long-term damage occurs when stands of coral are broken by freighters or boat anchors. Overfishing has caused the loss of coral-protecting sea urchins. This has left the coral vulnerable to the crown of thorns, a kind of coral-eating starfish.
Corals are small marine animals that stay in one place throughout their adult lives. These animals produce a hard skeleton made of calcium carbonate, or limestone. The skeletal material, which outlives the animal, is also called coral. Corals can be very colorful underwater, but most types fade when they die or are removed from the water. The red coral, found in the Mediterranean Sea and in the coastal waters of Japan, does not lose its color when removed from the water. Because of this quality it has been used in jewelry for centuries.
Where corals live
Corals live in all the oceans of the world. Many types grow in colonies that continue to enlarge year after year. Other types are solitary, meaning that they live alone. Several different types of corals can together form enormous colonies. These colonies are called coral reefs, coral islands, and coral atolls. The largest reefs are found in the warmer portions of the Pacific and Indian oceans. However, coral reefs are also found in the Caribbean and in the Gulf of Mexico as far north as southern Florida.
Coral reefs are composed of different types of corals. The reefs create underwater habitats that are essential for many species of marine organisms. Certain kinds of fish spend their life among the corals, using them as a refuge from predators. The largest coral reef in the world, the Great Barrier Reef off the coast of Australia, is more than 1,250 miles (2,000 kilometers) long. More than 350 species of coral have been found in the Great Barrier Reef.
Physical characteristics
Coral reefs have different shapes and patterns because of the growth pattern of the millions of tiny individual animals that make up a colony. Reefs can look like beautiful underwater gardens. Some corals resemble the tendrils of plants, while some may look like leaves. The brain coral is nearly spherical and has grooves that make it look like a human brain. Corals with flat, fan-shaped structures that spread out from a narrower base are called sea fans. The organ-pipe corals, which are found in the tropical oceans of the Indo-Pacific, are typically long rigid tubes.
The corals' skeletons, external or internal, have a stonelike, horny, or leathery texture. The body of a coral animal consists of a polyp—a hollow, cylindrical structure attached at its lower end to some surface. The largest of the solitary polyps grows to a diameter of about 10 inches (25 centimeters). The polyps of the corals that form reefs range from 0.04 to 1.2 inches (0.1 to 3 centimeters) in diameter.
Life cycle
Corals reproduce in two different ways. In one process, fertilized eggs develop into tiny, swimming organisms called planulae. Planulae eventually settle on the bottom of the ocean, on a rock or on another coral, and develop into polyps. Each polyp builds a limestone skeleton attached to the surface on which the polyp has landed. After the coral establishes itself, the upper part of the body becomes dome-shaped and develops a stomach and mouth.
Reproduction also can occur by budding. A bud develops the body of a polyp and remains attached there. A colony develops by the constant addition and growth of new buds. As new polyps develop, the older, underlying polyps die, leaving behind their skeletons. In some kinds of coral the buds may break away to become separate individuals. Vast coral colonies are built by budding, with the animals connected by their extensive skeletal network.
Food habits
Small marine organisms are the major food of corals. At the free end of the polyp is a mouth surrounded by tentacles. The tentacles gather food from the surrounding waters. Corals are also armed with specialized stinging structures, called nematocysts, that paralyze their prey. Nutrients are passed from individual corals on the outside of a colony to those on the inside.
Ecological issues
By the 1990s coral reefs off the coasts of more than 20 countries were being destroyed for a number of reasons. Rising water temperature is said to cause bleaching, which the corals cannot withstand. Oil spills and chemical pollution also are a major threat to corals. Long-term damage occurs when stands of coral are broken by freighters or boat anchors. Overfishing has caused the loss of coral-protecting sea urchins. This has left the coral vulnerable to the crown of thorns, a kind of coral-eating starfish.
Scientist
05-12-2007, 12:06
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
Coral snakes are poisonous snakes marked with bands of red, black, and yellow or white. These markings warn other animals that the snake is dangerous. The short, hollow fangs of coral snakes deliver a powerful venom that attacks the nervous system and can be deadly to human beings.
Where coral snakes live
About 65 kinds of coral snakes live in North and South America. They inhabit an area from the southern United States to central Argentina. Coral snakes live in a variety of places, including grasslands, rocky hillsides, tropical forests, and deserts.
Physical features
The bodies of coral snakes are made for burrowing, and they have narrow heads and slender bodies with long, pointed tails. Most coral snakes measure less than 3 feet (0.9 meter) long, but some South American varieties can grow longer than 4 feet (1.2 meters).
The eastern coral snake lives from the southeastern United States to northeastern Mexico. It has a black snout and narrow yellow bands separating wide bands of red and black. A few poisonous snakes in Africa, Australia, Asia are also known as coral snakes, but their coloring and markings vary and include stripes and spots.
Behavior
Coral snakes remain hidden most of the time, but they do come out to prowl and feed on other snakes and small lizards. When threatened, they may hide their heads in their coils and curl up their tails to look like heads. Some coral snakes respond to danger by making jerky movements or trying to bite. Others expel air from an opening called the vent, which makes a popping or gurgling sound.
Female coral snakes bury their eggs in leaves or other material. After hatching, the snakes use their rounded snouts to burrow in animal tunnels, decaying logs and leaves, and under rocks.
Coral snakes are poisonous snakes marked with bands of red, black, and yellow or white. These markings warn other animals that the snake is dangerous. The short, hollow fangs of coral snakes deliver a powerful venom that attacks the nervous system and can be deadly to human beings.
Where coral snakes live
About 65 kinds of coral snakes live in North and South America. They inhabit an area from the southern United States to central Argentina. Coral snakes live in a variety of places, including grasslands, rocky hillsides, tropical forests, and deserts.
Physical features
The bodies of coral snakes are made for burrowing, and they have narrow heads and slender bodies with long, pointed tails. Most coral snakes measure less than 3 feet (0.9 meter) long, but some South American varieties can grow longer than 4 feet (1.2 meters).
The eastern coral snake lives from the southeastern United States to northeastern Mexico. It has a black snout and narrow yellow bands separating wide bands of red and black. A few poisonous snakes in Africa, Australia, Asia are also known as coral snakes, but their coloring and markings vary and include stripes and spots.
Behavior
Coral snakes remain hidden most of the time, but they do come out to prowl and feed on other snakes and small lizards. When threatened, they may hide their heads in their coils and curl up their tails to look like heads. Some coral snakes respond to danger by making jerky movements or trying to bite. Others expel air from an opening called the vent, which makes a popping or gurgling sound.
Female coral snakes bury their eggs in leaves or other material. After hatching, the snakes use their rounded snouts to burrow in animal tunnels, decaying logs and leaves, and under rocks.
Scientist
05-12-2007, 12:06
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
The coyote is the most common and widespread native North American relative of the dog. An animal known for its swiftness and cunning, the coyote has also been called prairie wolf, brush wolf, and little wolf. The name coyote is taken from the word coyotl in the Aztec language.
Where coyotes live
Before the coming of settlers from the Old World, coyotes lived mostly in the grasslands of the western part of North America. The image of the howling coyote with its head upraised, silhouetted against the moon, has come to symbolize the Wild West. In recent times coyotes have moved into all regions of the continental United States, probably because few wolves remain to prey upon them or compete with them for food.
Physical characteristics
The coyote is smaller than the wolf. Most adults weigh 20–40 pounds (9–18 kilograms), stand 24 inches (60 centimeters) at the shoulder, and measure 48–60 inches (122–152 centimeters) nose to tail. Males tend to be larger than females. The coat is typically long and full and may make the animal appear to be larger than it really is. Colors vary, but most animals are grayish brown, with whitish underparts and a bushy tail with a black tip. Captive coyotes have lived 18 years or more, but life expectancy is much shorter in the wild.
Behavior
When a coyote howls it is usually proclaiming its territory to other coyotes. Coyotes can be active at any time of the day or night, but are most often seen in the hours of dusk or dawn. Coyotes are predators capable of hunting alone, with a mate, or in a pack. Coyotes can hunt by stealth but are also capable of rapid pursuit. With a top speed of 40 miles (64 kilometers) per hour they are one of North America's fastest land animals.
The coyote's diet is typically based on rodents, rabbits, and hares, but packs may pursue larger prey, including sheep. In addition to live prey, coyotes also feed on carcasses of dead animals. Sometimes they eat plants as well.
Life cycle
The basic social unit of the coyote is the breeding pair. Pairs sometimes stay together for life. Mating takes place in the winter. Two months later a litter of about six pups is born in a den. The den is usually a burrow in the ground. The newborn pups are blind and helpless, just like the puppies of a domestic dog. Their parents feed them and soon teach them to hunt. Sometimes full-grown pups will stay with their parents and help with the care of the next year's litter. An individual leaving home may have to travel a long distance before it can establish its own territory.
Other issues
Coyotes have proved that they are adaptable by expanding their range in the face of persistent attacks by humans. Individuals frequently turn up in populated areas, even in the largest cities. Coyotes will mate readily with domestic dogs, producing hybrid offspring called coydogs.
The coyote is the most common and widespread native North American relative of the dog. An animal known for its swiftness and cunning, the coyote has also been called prairie wolf, brush wolf, and little wolf. The name coyote is taken from the word coyotl in the Aztec language.
Where coyotes live
Before the coming of settlers from the Old World, coyotes lived mostly in the grasslands of the western part of North America. The image of the howling coyote with its head upraised, silhouetted against the moon, has come to symbolize the Wild West. In recent times coyotes have moved into all regions of the continental United States, probably because few wolves remain to prey upon them or compete with them for food.
Physical characteristics
The coyote is smaller than the wolf. Most adults weigh 20–40 pounds (9–18 kilograms), stand 24 inches (60 centimeters) at the shoulder, and measure 48–60 inches (122–152 centimeters) nose to tail. Males tend to be larger than females. The coat is typically long and full and may make the animal appear to be larger than it really is. Colors vary, but most animals are grayish brown, with whitish underparts and a bushy tail with a black tip. Captive coyotes have lived 18 years or more, but life expectancy is much shorter in the wild.
Behavior
When a coyote howls it is usually proclaiming its territory to other coyotes. Coyotes can be active at any time of the day or night, but are most often seen in the hours of dusk or dawn. Coyotes are predators capable of hunting alone, with a mate, or in a pack. Coyotes can hunt by stealth but are also capable of rapid pursuit. With a top speed of 40 miles (64 kilometers) per hour they are one of North America's fastest land animals.
The coyote's diet is typically based on rodents, rabbits, and hares, but packs may pursue larger prey, including sheep. In addition to live prey, coyotes also feed on carcasses of dead animals. Sometimes they eat plants as well.
Life cycle
The basic social unit of the coyote is the breeding pair. Pairs sometimes stay together for life. Mating takes place in the winter. Two months later a litter of about six pups is born in a den. The den is usually a burrow in the ground. The newborn pups are blind and helpless, just like the puppies of a domestic dog. Their parents feed them and soon teach them to hunt. Sometimes full-grown pups will stay with their parents and help with the care of the next year's litter. An individual leaving home may have to travel a long distance before it can establish its own territory.
Other issues
Coyotes have proved that they are adaptable by expanding their range in the face of persistent attacks by humans. Individuals frequently turn up in populated areas, even in the largest cities. Coyotes will mate readily with domestic dogs, producing hybrid offspring called coydogs.
Scientist
05-12-2007, 12:08
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
There are about 4,500 species, or kinds, of the crustaceans known as crabs. Some types, including the blue crab, the Dungeness crab, and the king crab, are often eaten by humans. Crabs may be sold fresh to restaurants, or their meat may be canned.
Where crabs live
Crabs can be found in all oceans and in freshwater. Some crabs live on land, sometimes several miles from water. Species such as the fiddler crab live in burrows in the sand or mud, where they stay during winter and high tides. Others live within the shells of oysters or mussels.
Physical features
Crabs and other crustaceans have a hard covering known as the exoskeleton. Like its relative the lobster, a crab has five pairs of legs. The first pair has large pinching claws that help with feeding and defense. The last pair may be broad and flattened to serve as paddles for crabs that swim. The tail of a crab is curled under its midsection. Crabs breathe by using gills, but the gills of land crabs have developed in such a way that they act like lungs.
Crabs have broader bodies than other crustaceans. They come in a great range of sizes. Tiny pea crabs may measure less than an inch (2.5 centimeters) across. The giant crab of Japan, on the other hand, may be more than 1 foot (30 centimeters) across and measure 12 feet (4 meters) from tip to tip of its outstretched legs.
Behavior
Most crabs are scavengers, meaning they eat dead or decaying material. Some crabs may feed on vegetable matter, and others eat small living animals. The crab can see movement through its two large eyes, which extend from the head on movable stalks located above the two pairs of antennae. The mouth is on the underside of the head.
One group of crabs, the hermits, are known for their habit of taking over empty snail shells for shelter. A hermit crab drags the shell behind it as it walks about. As the crab grows larger, it seeks a larger shell.
Reproduction and growth
All female crabs, including land crabs, must return to the water to lay eggs. The eggs are carried on the female's body until they hatch. For the blue crab, this might mean carrying some 2 million eggs at a time. Although a few baby crabs leave the egg looking like small adults, most do not. Instead, a newly hatched crab is usually a tiny, see-through, legless creature that swims at the top of the water. At this stage the animal is called a zoea. As a result of a process called metamorphosis, during which it molts (sheds its outside covering) many times, the youngster becomes an adult crab.
There are about 4,500 species, or kinds, of the crustaceans known as crabs. Some types, including the blue crab, the Dungeness crab, and the king crab, are often eaten by humans. Crabs may be sold fresh to restaurants, or their meat may be canned.
Where crabs live
Crabs can be found in all oceans and in freshwater. Some crabs live on land, sometimes several miles from water. Species such as the fiddler crab live in burrows in the sand or mud, where they stay during winter and high tides. Others live within the shells of oysters or mussels.
Physical features
Crabs and other crustaceans have a hard covering known as the exoskeleton. Like its relative the lobster, a crab has five pairs of legs. The first pair has large pinching claws that help with feeding and defense. The last pair may be broad and flattened to serve as paddles for crabs that swim. The tail of a crab is curled under its midsection. Crabs breathe by using gills, but the gills of land crabs have developed in such a way that they act like lungs.
Crabs have broader bodies than other crustaceans. They come in a great range of sizes. Tiny pea crabs may measure less than an inch (2.5 centimeters) across. The giant crab of Japan, on the other hand, may be more than 1 foot (30 centimeters) across and measure 12 feet (4 meters) from tip to tip of its outstretched legs.
Behavior
Most crabs are scavengers, meaning they eat dead or decaying material. Some crabs may feed on vegetable matter, and others eat small living animals. The crab can see movement through its two large eyes, which extend from the head on movable stalks located above the two pairs of antennae. The mouth is on the underside of the head.
One group of crabs, the hermits, are known for their habit of taking over empty snail shells for shelter. A hermit crab drags the shell behind it as it walks about. As the crab grows larger, it seeks a larger shell.
Reproduction and growth
All female crabs, including land crabs, must return to the water to lay eggs. The eggs are carried on the female's body until they hatch. For the blue crab, this might mean carrying some 2 million eggs at a time. Although a few baby crabs leave the egg looking like small adults, most do not. Instead, a newly hatched crab is usually a tiny, see-through, legless creature that swims at the top of the water. At this stage the animal is called a zoea. As a result of a process called metamorphosis, during which it molts (sheds its outside covering) many times, the youngster becomes an adult crab.
Scientist
05-12-2007, 12:40
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
The crane is a tall, graceful, wading bird. It is also very cautious and can detect the faintest sound or sight of danger.
Where cranes live
Most cranes are migratory, which means they travel from one place to another depending on the season. Cranes live all over the world, including Europe, Asia, and Africa.
Physical features
Cranes are tall birds. For example, the whooping crane is more than 4 feet (1.2 meters) tall and has a wingspan of 7 feet (2.1 meters). It is white with black wing tips and has a red cap and face.
Cranes have feathers that grow close to their bodies and look smooth. They have three front toes and one back toe, with the back toe higher on the leg than the front toes. When a crane flies, it stretches its neck forward and holds it out in front. Cranes make a piercing, trumpetlike call that can be heard long after they have flown out of sight. This call comes from the crane's windpipe, which is coiled and twisted like a horn.
Behavior
Cranes eat a wide variety of food, such as small animals, fish, insects, frogs, salamanders, lizards, mice, grasshoppers, grass shoots, and even grains. They perform courtship dances by hopping and flapping their wings while making their calls.
Reproduction
Male cranes usually begin courting female cranes in the spring. Female cranes usually lay two or sometimes three shiny olive-gray eggs with brown spots. The nest is in the ground and lined with grass, reeds, rushes, or stems. The same nest may be used year after year. The young are covered with a full coat of soft, fluffy, brown down. They begin running around within a few hours of hatching. By autumn the young are strong enough to join the long flight to their winter grounds with the adults.
Threats to cranes
Many kinds of cranes are endangered because of hunting and habitat destruction. The North American whooping crane was quite common at the beginning of the 20th century but is now so rare that it is protected in a special sanctuary in Texas. Strict laws and protected areas for breeding have saved these birds.
The crane is a tall, graceful, wading bird. It is also very cautious and can detect the faintest sound or sight of danger.
Where cranes live
Most cranes are migratory, which means they travel from one place to another depending on the season. Cranes live all over the world, including Europe, Asia, and Africa.
Physical features
Cranes are tall birds. For example, the whooping crane is more than 4 feet (1.2 meters) tall and has a wingspan of 7 feet (2.1 meters). It is white with black wing tips and has a red cap and face.
Cranes have feathers that grow close to their bodies and look smooth. They have three front toes and one back toe, with the back toe higher on the leg than the front toes. When a crane flies, it stretches its neck forward and holds it out in front. Cranes make a piercing, trumpetlike call that can be heard long after they have flown out of sight. This call comes from the crane's windpipe, which is coiled and twisted like a horn.
Behavior
Cranes eat a wide variety of food, such as small animals, fish, insects, frogs, salamanders, lizards, mice, grasshoppers, grass shoots, and even grains. They perform courtship dances by hopping and flapping their wings while making their calls.
Reproduction
Male cranes usually begin courting female cranes in the spring. Female cranes usually lay two or sometimes three shiny olive-gray eggs with brown spots. The nest is in the ground and lined with grass, reeds, rushes, or stems. The same nest may be used year after year. The young are covered with a full coat of soft, fluffy, brown down. They begin running around within a few hours of hatching. By autumn the young are strong enough to join the long flight to their winter grounds with the adults.
Threats to cranes
Many kinds of cranes are endangered because of hunting and habitat destruction. The North American whooping crane was quite common at the beginning of the 20th century but is now so rare that it is protected in a special sanctuary in Texas. Strict laws and protected areas for breeding have saved these birds.
Scientist
05-12-2007, 12:45
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
The crocodile is a lizard-like, flesh-eating reptile. It is the largest and heaviest of all present-day reptiles. It is related to the alligator.
Where crocodiles live
Crocodiles live in swamps, lakes, and rivers in tropical and sub-tropical regions. They are found in Africa, Madagascar, India, Sri Lanka, southeast Asia, northern Australia, Mexico, the West Indies, and the Americas. The American crocodile is the only species that lives outside the tropics.
Physical features
Crocodiles have many interesting physical features that are useful for living in the water and catching their prey. Crocodiles have long snouts that vary in proportion and shape. They have a tough skin covered with large horny plates called scutes. Thick bony plates cover their back.
Because their eyes and nostrils are on top of their head, crocodiles can see and breathe even when their body is submerged in water. This helps them surprise and catch larger prey.
In addition, crocodiles have external ears that close when they dive in water. The third eyelid, or the nictitating membrane, is another feature that helps them to live in water. This clear membrane closes while the eyelids remain open, allowing the crocodile to see under water.
Crocodiles also have short and powerful legs. Their front legs have five toes, and their hind legs have four wholly or partially webbed toes.
Although crocodiles look like alligators, it is easy to tell them apart. The fourth tooth in the lower jaw of crocodiles always sticks out, whereas in alligators it fits into a socket in the upper jaw.
There are about a dozen known species of crocodiles, all of which vary greatly in size. The dwarf crocodile of the West African rain forests measures only 6 feet (1.8 meters) in length. The giant estuarine crocodile of tropical Asia and Australia, on the other hand, may grow to almost 30 feet (9 meters). This type of crocodile is the largest living reptile in the world.
Behavior
Young crocodiles feed on insects, frogs, and small fish. Adult crocodiles feed on larger fishes, turtles, and birds. Crocodiles capture water animals in their jaws with a sideways movement of the muzzle. To capture land animals, they wait motionless at waterhole edges. In a surprise attack, crocodiles seize their prey by the feet and drag it quickly toward the water. Sometimes they knock the prey off balance with their tails. When they cannot consume the whole prey, they store it in their burrows. Some crocodiles, such as the Nile crocodile and the estuarine crocodile, have been known to attack humans.
Among all reptiles, crocodiles have the most highly developed brains. They are very curious and can be tamed. If kept captive from birth, some crocodiles learn to recognize their keepers. In captivity, they do not show fear or aggression, they beg for food, and they accept being petted. In other words, they change their behavior to adapt to the environment of captivity.
Life cycle
Crocodiles reproduce by laying hard-shelled eggs. Some crocodiles can lay more than 100 eggs. The female builds nests of mud and dead leaves as shelter for the eggs. As the plants rot, they give off enough warmth to help the eggs hatch. The female remains close to the nest and protects the eggs from predators until the eggs hatch. While still in the egg, the baby crocodiles utter squeaking sounds, perhaps indicating that they are ready to be born. The female then removes the dirt or other debris from the eggs. After that, she does not provide any more care for them; they are on their own. In most species, the young move by instinct toward the water. However, the female Nile crocodile carries the hatchlings to the water in her mouth.
Newborn crocodiles are about 8–10 inches (20–25 centimeters) long. They remain hidden at the water's edge to escape predators, which include fish, birds, and larger crocodiles. During the first three to four years, the young increase in length by about 1 foot (about 30 centimeters) per year. The growth rate then gradually decreases, but growth can continue throughout life.
Environmental issues
The American crocodile and the mugger, or marsh crocodile, are endangered species. Their habitat changed because of city development, making it difficult to live. Also, they were killed for their skins.
The crocodile is a lizard-like, flesh-eating reptile. It is the largest and heaviest of all present-day reptiles. It is related to the alligator.
Where crocodiles live
Crocodiles live in swamps, lakes, and rivers in tropical and sub-tropical regions. They are found in Africa, Madagascar, India, Sri Lanka, southeast Asia, northern Australia, Mexico, the West Indies, and the Americas. The American crocodile is the only species that lives outside the tropics.
Physical features
Crocodiles have many interesting physical features that are useful for living in the water and catching their prey. Crocodiles have long snouts that vary in proportion and shape. They have a tough skin covered with large horny plates called scutes. Thick bony plates cover their back.
Because their eyes and nostrils are on top of their head, crocodiles can see and breathe even when their body is submerged in water. This helps them surprise and catch larger prey.
In addition, crocodiles have external ears that close when they dive in water. The third eyelid, or the nictitating membrane, is another feature that helps them to live in water. This clear membrane closes while the eyelids remain open, allowing the crocodile to see under water.
Crocodiles also have short and powerful legs. Their front legs have five toes, and their hind legs have four wholly or partially webbed toes.
Although crocodiles look like alligators, it is easy to tell them apart. The fourth tooth in the lower jaw of crocodiles always sticks out, whereas in alligators it fits into a socket in the upper jaw.
There are about a dozen known species of crocodiles, all of which vary greatly in size. The dwarf crocodile of the West African rain forests measures only 6 feet (1.8 meters) in length. The giant estuarine crocodile of tropical Asia and Australia, on the other hand, may grow to almost 30 feet (9 meters). This type of crocodile is the largest living reptile in the world.
Behavior
Young crocodiles feed on insects, frogs, and small fish. Adult crocodiles feed on larger fishes, turtles, and birds. Crocodiles capture water animals in their jaws with a sideways movement of the muzzle. To capture land animals, they wait motionless at waterhole edges. In a surprise attack, crocodiles seize their prey by the feet and drag it quickly toward the water. Sometimes they knock the prey off balance with their tails. When they cannot consume the whole prey, they store it in their burrows. Some crocodiles, such as the Nile crocodile and the estuarine crocodile, have been known to attack humans.
Among all reptiles, crocodiles have the most highly developed brains. They are very curious and can be tamed. If kept captive from birth, some crocodiles learn to recognize their keepers. In captivity, they do not show fear or aggression, they beg for food, and they accept being petted. In other words, they change their behavior to adapt to the environment of captivity.
Life cycle
Crocodiles reproduce by laying hard-shelled eggs. Some crocodiles can lay more than 100 eggs. The female builds nests of mud and dead leaves as shelter for the eggs. As the plants rot, they give off enough warmth to help the eggs hatch. The female remains close to the nest and protects the eggs from predators until the eggs hatch. While still in the egg, the baby crocodiles utter squeaking sounds, perhaps indicating that they are ready to be born. The female then removes the dirt or other debris from the eggs. After that, she does not provide any more care for them; they are on their own. In most species, the young move by instinct toward the water. However, the female Nile crocodile carries the hatchlings to the water in her mouth.
Newborn crocodiles are about 8–10 inches (20–25 centimeters) long. They remain hidden at the water's edge to escape predators, which include fish, birds, and larger crocodiles. During the first three to four years, the young increase in length by about 1 foot (about 30 centimeters) per year. The growth rate then gradually decreases, but growth can continue throughout life.
Environmental issues
The American crocodile and the mugger, or marsh crocodile, are endangered species. Their habitat changed because of city development, making it difficult to live. Also, they were killed for their skins.
Scientist
05-12-2007, 12:48
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Crows are named after their typical call, which sounds like “caw” or “crah.” These birds are also known for their shiny black feathers and great intelligence.
Where crows live
The common American crow can be found as far north as the Arctic Circle and as far south as Florida, the Gulf coast, and northern Mexico. This crow's habitat includes wooded areas, farmland, and even suburban areas. The fish crow, also from North America, is a coastal bird that lives along the Eastern seaboard, the Florida coast, and the Gulf of Mexico. Other well-known species include the carrion crow of Eurasia; the Indian house crow, which is found from India to Malaysia; and the pied crow of tropical Africa.
Crows often flock together in great numbers, but most species do not nest in colonies, or large groups. Each mating pair has its own nest. Crows do not migrate long distances, but thousands will sometimes spend the night together at a common place before leaving each morning to their various feeding grounds.
Physical characteristics
All true crows are glossy black and about 20 inches (50 centimeters) long. The pied crow of Africa has a white nape and breast. Crows have powerful beaks, which they use for catching small animals and for opening seeds. Males and females usually look alike.
Behavior
Because crows eat a wide variety of plant and animal foods, they are a big nuisance to farmers. They usually eat fruits, corn and other grains, and insects, including harmful pests. They have also been known to eat baby birds, rabbits, mice, and snakes. They feed mainly on the ground.
Life cycle
Crows mate in early spring and build large stick nests on the tops of tall trees. The female crow lays about four or six eggs. They are dull green with dark brown spots. While the female sits on the eggs, the male takes on the duty of providing her, and later their chicks, with food. Because crow chicks eat a lot, both parents are busy with feeding. Crows have a natural life span of about 13 years, but in captivity they can live up to 20 years or more.
Crows as pets
Crows are considered to be among the most intelligent birds. Young crows can be entertaining pets and can be taught to perform simple tricks. Pet crows have even been taught to talk like parrots. They are also thieves and will steal any little trinket or shiny object.
Crows are named after their typical call, which sounds like “caw” or “crah.” These birds are also known for their shiny black feathers and great intelligence.
Where crows live
The common American crow can be found as far north as the Arctic Circle and as far south as Florida, the Gulf coast, and northern Mexico. This crow's habitat includes wooded areas, farmland, and even suburban areas. The fish crow, also from North America, is a coastal bird that lives along the Eastern seaboard, the Florida coast, and the Gulf of Mexico. Other well-known species include the carrion crow of Eurasia; the Indian house crow, which is found from India to Malaysia; and the pied crow of tropical Africa.
Crows often flock together in great numbers, but most species do not nest in colonies, or large groups. Each mating pair has its own nest. Crows do not migrate long distances, but thousands will sometimes spend the night together at a common place before leaving each morning to their various feeding grounds.
Physical characteristics
All true crows are glossy black and about 20 inches (50 centimeters) long. The pied crow of Africa has a white nape and breast. Crows have powerful beaks, which they use for catching small animals and for opening seeds. Males and females usually look alike.
Behavior
Because crows eat a wide variety of plant and animal foods, they are a big nuisance to farmers. They usually eat fruits, corn and other grains, and insects, including harmful pests. They have also been known to eat baby birds, rabbits, mice, and snakes. They feed mainly on the ground.
Life cycle
Crows mate in early spring and build large stick nests on the tops of tall trees. The female crow lays about four or six eggs. They are dull green with dark brown spots. While the female sits on the eggs, the male takes on the duty of providing her, and later their chicks, with food. Because crow chicks eat a lot, both parents are busy with feeding. Crows have a natural life span of about 13 years, but in captivity they can live up to 20 years or more.
Crows as pets
Crows are considered to be among the most intelligent birds. Young crows can be entertaining pets and can be taught to perform simple tricks. Pet crows have even been taught to talk like parrots. They are also thieves and will steal any little trinket or shiny object.
Scientist
05-12-2007, 12:53
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Crustaceans are animals with hard shells. Crabs, lobsters, shrimp, and wood lice are among some of the best-known crustaceans.
Where crustaceans live
Crustaceans are found throughout the world, mainly in water. There are freshwater and saltwater crustaceans. For example, some species live in the open waters of lakes and oceans. Other species live at the bottom of the sea, in places as deep as 32,808 feet (10,000 meters). Some can be found in rocky, sandy, and muddy areas. Some are so small that they live in the spaces between sand grains. Others tunnel in the leaves of seaweeds or into wooden structures.
Crustaceans inhabit even high mountain lakes at altitudes of 16,404 feet (5,000 meters). A number of crabs are amphibious, meaning that they live in both land and water. The most terrestrial, or land-inhabiting, crustaceans are the wood lice. Most of them live in damp places, though a few species can survive even in deserts. Some crustaceans are found among damp leaves on forest floors, particularly in the tropics.
Physical features
The basic crustacean body consists of a number of segments. At the front end of the body there is a region called the acron, which is the head on most crustaceans. The tail ends of crustacean bodies differ greatly in form. In many crustaceans the tail is short, but in some it may be as long as the rest of the body.
The shell is a common crustacean feature. This shell is occasionally shed because its hard structure does not allow growth. Adult crustaceans have two pairs of antennae. Crustaceans may also have other features such as legs or gills.
The largest crustaceans include the American lobster, which can reach a weight of 44 pounds (20 kilograms), and the giant Japanese spider crab, which has legs that can span up to 12 feet (3.7 meters). At the other end of the scale, some water fleas reach lengths of less than 0.009 inch (0.25 millimeter).
Life cycle
In crustaceans the male and female sexes are normally, but not always, separate. The marine crustacean called a barnacle has male and female reproductive organs in one individual. Some types of shrimp change their --- during their lifetime. They begin life as males but change into females after about 13 months.
Some crustaceans lay their eggs freely in the water. Others carry the eggs attached to part of their body until the eggs are ready to hatch. In some crustaceans, the young resemble adults when they hatch from the eggs. This trait is found in many species of crabs and crayfish.
Uses
Crustaceans are valuable sources of food. People in many parts of the world capture shrimp, prawns, lobsters, crayfish, and crabs. In Japan, barnacles are allowed to settle and grow on bamboo stakes. Later these barnacles are scraped off and crushed for use as fertilizer.
Crustaceans are animals with hard shells. Crabs, lobsters, shrimp, and wood lice are among some of the best-known crustaceans.
Where crustaceans live
Crustaceans are found throughout the world, mainly in water. There are freshwater and saltwater crustaceans. For example, some species live in the open waters of lakes and oceans. Other species live at the bottom of the sea, in places as deep as 32,808 feet (10,000 meters). Some can be found in rocky, sandy, and muddy areas. Some are so small that they live in the spaces between sand grains. Others tunnel in the leaves of seaweeds or into wooden structures.
Crustaceans inhabit even high mountain lakes at altitudes of 16,404 feet (5,000 meters). A number of crabs are amphibious, meaning that they live in both land and water. The most terrestrial, or land-inhabiting, crustaceans are the wood lice. Most of them live in damp places, though a few species can survive even in deserts. Some crustaceans are found among damp leaves on forest floors, particularly in the tropics.
Physical features
The basic crustacean body consists of a number of segments. At the front end of the body there is a region called the acron, which is the head on most crustaceans. The tail ends of crustacean bodies differ greatly in form. In many crustaceans the tail is short, but in some it may be as long as the rest of the body.
The shell is a common crustacean feature. This shell is occasionally shed because its hard structure does not allow growth. Adult crustaceans have two pairs of antennae. Crustaceans may also have other features such as legs or gills.
The largest crustaceans include the American lobster, which can reach a weight of 44 pounds (20 kilograms), and the giant Japanese spider crab, which has legs that can span up to 12 feet (3.7 meters). At the other end of the scale, some water fleas reach lengths of less than 0.009 inch (0.25 millimeter).
Life cycle
In crustaceans the male and female sexes are normally, but not always, separate. The marine crustacean called a barnacle has male and female reproductive organs in one individual. Some types of shrimp change their --- during their lifetime. They begin life as males but change into females after about 13 months.
Some crustaceans lay their eggs freely in the water. Others carry the eggs attached to part of their body until the eggs are ready to hatch. In some crustaceans, the young resemble adults when they hatch from the eggs. This trait is found in many species of crabs and crayfish.
Uses
Crustaceans are valuable sources of food. People in many parts of the world capture shrimp, prawns, lobsters, crayfish, and crabs. In Japan, barnacles are allowed to settle and grow on bamboo stakes. Later these barnacles are scraped off and crushed for use as fertilizer.
Scientist
05-12-2007, 12:56
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The birds known as cuckoos are named for the sounds they make. Because of their shy personality, these birds are more often heard than seen.
Where cuckoos live
Cuckoos are found throughout the world. They tend to hide in thick vegetation. Two kinds of cuckoos in North America are the black-billed cuckoo and the yellow-billed cuckoo. These birds migrate to the tropics for the winter. The common cuckoo is found throughout Europe and most of Asia. This bird migrates to Africa for the winter.
Physical characteristics
Cuckoos range in length from about 612 to 36 inches (17 to 91 centimeters). Most are drab gray and brown, but a few have bright patches of red or white. One kind of cuckoo, called the glossy cuckoo, has a shining emerald green color. Some of the cuckoos that live in tropical areas have blue feathers on their backs and wings. Most cuckoos are short-winged. All have long tails, usually with the individual feathers tipped with white. The legs are medium to rather long in size. The outer toes on the feet are reversed, which means they point backward. The bill is short and curves down a bit.
Behavior
Cuckoos feed on insects, including the hairy caterpillar. Because hairy caterpillars are poisonous, most birds will not touch them. However, cuckoos have a special way of eating them so they do not eat the poison.
Cuckoos are best known for their habit of laying eggs in the nests of certain other kinds of birds. The other birds keep the cuckoo's eggs warm and care for the young cuckoos.
The birds known as cuckoos are named for the sounds they make. Because of their shy personality, these birds are more often heard than seen.
Where cuckoos live
Cuckoos are found throughout the world. They tend to hide in thick vegetation. Two kinds of cuckoos in North America are the black-billed cuckoo and the yellow-billed cuckoo. These birds migrate to the tropics for the winter. The common cuckoo is found throughout Europe and most of Asia. This bird migrates to Africa for the winter.
Physical characteristics
Cuckoos range in length from about 612 to 36 inches (17 to 91 centimeters). Most are drab gray and brown, but a few have bright patches of red or white. One kind of cuckoo, called the glossy cuckoo, has a shining emerald green color. Some of the cuckoos that live in tropical areas have blue feathers on their backs and wings. Most cuckoos are short-winged. All have long tails, usually with the individual feathers tipped with white. The legs are medium to rather long in size. The outer toes on the feet are reversed, which means they point backward. The bill is short and curves down a bit.
Behavior
Cuckoos feed on insects, including the hairy caterpillar. Because hairy caterpillars are poisonous, most birds will not touch them. However, cuckoos have a special way of eating them so they do not eat the poison.
Cuckoos are best known for their habit of laying eggs in the nests of certain other kinds of birds. The other birds keep the cuckoo's eggs warm and care for the young cuckoos.
Scientist
05-12-2007, 13:00
Deep within the world's seas and oceans is an area called the abyssal zone. It lies more than 6,000 feet (1,800 meters) below the surface of the water. It is totally dark there, and the water is almost motionless. Yet even in these conditions various forms of life survive. These range from tiny microorganisms to more complex animals such as fish and crustaceans.
Habitat
For a long time it was believed that there could be no plants in the dark bottom of the ocean because they require light. It was also thought that without plant life there could be no animal life. However, scientists descended to the bottom of the Atlantic Ocean's Puerto Rico Trench in 1964 and reported plenty of life even at the depth of 27,498 feet (8,381 meters).
In 1977 scientists discovered ocean-floor communities of previously unknown forms of life. They also discovered that these were grouped around fissures, or cracks, on the ocean floor. The cracks are gaps between two of the plates making up the Earth's crust. When the plates separate, the volcanic activity underneath the crust is exposed and hot minerals are released into the ocean. The forms of life gathered around the cracks are known as rift communities. They are able to survive in the harsh environment of the bottom of the sea because of the nutrients and warmth that seeps through the cracks.
Forms of life
Other than the rift communities, very little is known about the environment and behavior of most deep-sea species. It is difficult to observe and study animals at such depths. Several animal species in the deep-sea zone are related to groups that are found in shallower seas. Deep-sea species of squids, octopuses, worms, and mollusks have been found in these regions. Many fish families are also found at extreme depths. Because competition is less intense in the deep sea than in shallower waters, primitive types of fish still exist there.
The life forms around the rifts can be very large in size. Newly discovered clams are among the largest clams known, with some more than 10 inches (25 centimeters) long. Tubeworms are another discovery. They are large red worms encased upright in white tubes anchored to the ocean floor. They measure up to 5 feet (1.5 meters) in length, and are typically found in colonies.
Adaptation
Animal life in the deep seas has adapted itself in order to survive the constant cold, darkness, and strong pressure of the water. Some fish that survive in the deep sea have small, soft bodies with minimal bone structure to adapt to these conditions.
Many deep-sea fishes are able to generate their own light. This ability of living organisms to generate light is called bioluminescence. Their light-producing organs attract both prey and potential mates. Deep-sea angler fish, for example, have long filaments with a light on the end dangling over the top of their head. Other fishes mistake the light for small prey and swim into the angler's enormous mouth, where they are quickly eaten by the angler.
Habitat
For a long time it was believed that there could be no plants in the dark bottom of the ocean because they require light. It was also thought that without plant life there could be no animal life. However, scientists descended to the bottom of the Atlantic Ocean's Puerto Rico Trench in 1964 and reported plenty of life even at the depth of 27,498 feet (8,381 meters).
In 1977 scientists discovered ocean-floor communities of previously unknown forms of life. They also discovered that these were grouped around fissures, or cracks, on the ocean floor. The cracks are gaps between two of the plates making up the Earth's crust. When the plates separate, the volcanic activity underneath the crust is exposed and hot minerals are released into the ocean. The forms of life gathered around the cracks are known as rift communities. They are able to survive in the harsh environment of the bottom of the sea because of the nutrients and warmth that seeps through the cracks.
Forms of life
Other than the rift communities, very little is known about the environment and behavior of most deep-sea species. It is difficult to observe and study animals at such depths. Several animal species in the deep-sea zone are related to groups that are found in shallower seas. Deep-sea species of squids, octopuses, worms, and mollusks have been found in these regions. Many fish families are also found at extreme depths. Because competition is less intense in the deep sea than in shallower waters, primitive types of fish still exist there.
The life forms around the rifts can be very large in size. Newly discovered clams are among the largest clams known, with some more than 10 inches (25 centimeters) long. Tubeworms are another discovery. They are large red worms encased upright in white tubes anchored to the ocean floor. They measure up to 5 feet (1.5 meters) in length, and are typically found in colonies.
Adaptation
Animal life in the deep seas has adapted itself in order to survive the constant cold, darkness, and strong pressure of the water. Some fish that survive in the deep sea have small, soft bodies with minimal bone structure to adapt to these conditions.
Many deep-sea fishes are able to generate their own light. This ability of living organisms to generate light is called bioluminescence. Their light-producing organs attract both prey and potential mates. Deep-sea angler fish, for example, have long filaments with a light on the end dangling over the top of their head. Other fishes mistake the light for small prey and swim into the angler's enormous mouth, where they are quickly eaten by the angler.
Scientist
05-12-2007, 13:03
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The only animals with antlers on their heads are deer. Deer are hoofed mammals that belong to the scientific family Cervidae. There are more than 30 different species, or kinds, of deer. Among them are the moose, wapiti, and reindeer, or caribou.
Where deer live
Deer are native to Europe, Asia, North America, South America, and northern Africa. They have been introduced into such areas as the Hawaiian Islands, Australia, and New Zealand. They live in a wide variety of places, including forests, swamps, deserts, and tundra.
Physical features
Deer range in shoulder height from about 12 inches (30 centimeters) in the South American pudu to 7 feet (2.1 meters) or more in the moose. In most species females are somewhat smaller than males. Deer typically have compact bodies and short tails. The ears are large but usually slender. The legs are usually long and slender with paired hooves.
Deer are usually a shade of brown, often with white on the chest and throat. Generally the fur is slightly rough but has a smooth appearance. Some deer have a shaggier coat, especially in the cold seasons.
Except for female reindeer, only male deer grow antlers. The antlers are shed each year. Male deer use their antlers as weapons during the mating season to win the chance to mate with females. A buck, or male, develops a pair of spiked antlers by the fall of its second year. Between January and April, after mating, the buck sheds his antlers and grows a larger set.
Behavior
Deer are very cautious animals with a keen sense of smell and hearing. Most deer live in small family groups, though the males generally spend some time alone. Deer are most active in early morning and late afternoon, resting at midday and at night. Some types travel a long way from place to place for different seasons.
Deer eat only plant material such as grass, young shoots, twigs, and bark. They are ruminants, meaning that they digest their food in stages. Deer chew their food, swallow it, and then bring it back up from the stomach in a form called cud. After chewing the cud, they swallow again so the stomach can finish digestion.
In warm climates deer mate at any time of the year. In colder climates they breed in autumn or winter. Female deer give birth to one or two young or, occasionally, to triplets. The offspring nurse for several months. Most deer reach adulthood in one to three years.
Deer and humans
In colonial times the deer of North America were one of the most important wild game animals. Their meat, called venison, was a major food source for early settlers. Deerskin was used to make jackets, moccasins, and other leather goods. White-tailed deer are still the most popular large game animal in the eastern United States.
White-tailed deer are considered nuisances in some areas because there are so many of them. They destroy shrubs and plants and carry ticks that spread Lyme disease. Deer also cause thousands of traffic accidents each year. Some experts believe that hunting is the best way to control white-tailed deer populations.
For some deer species, however, hunting is a serious threat to survival. Another great danger for deer is the loss of their natural homes. People have cleared much of the land where deer lived for farmland and for other purposes. To protect the remaining deer, many places have banned deer hunting and set aside land where deer can live safely.
The only animals with antlers on their heads are deer. Deer are hoofed mammals that belong to the scientific family Cervidae. There are more than 30 different species, or kinds, of deer. Among them are the moose, wapiti, and reindeer, or caribou.
Where deer live
Deer are native to Europe, Asia, North America, South America, and northern Africa. They have been introduced into such areas as the Hawaiian Islands, Australia, and New Zealand. They live in a wide variety of places, including forests, swamps, deserts, and tundra.
Physical features
Deer range in shoulder height from about 12 inches (30 centimeters) in the South American pudu to 7 feet (2.1 meters) or more in the moose. In most species females are somewhat smaller than males. Deer typically have compact bodies and short tails. The ears are large but usually slender. The legs are usually long and slender with paired hooves.
Deer are usually a shade of brown, often with white on the chest and throat. Generally the fur is slightly rough but has a smooth appearance. Some deer have a shaggier coat, especially in the cold seasons.
Except for female reindeer, only male deer grow antlers. The antlers are shed each year. Male deer use their antlers as weapons during the mating season to win the chance to mate with females. A buck, or male, develops a pair of spiked antlers by the fall of its second year. Between January and April, after mating, the buck sheds his antlers and grows a larger set.
Behavior
Deer are very cautious animals with a keen sense of smell and hearing. Most deer live in small family groups, though the males generally spend some time alone. Deer are most active in early morning and late afternoon, resting at midday and at night. Some types travel a long way from place to place for different seasons.
Deer eat only plant material such as grass, young shoots, twigs, and bark. They are ruminants, meaning that they digest their food in stages. Deer chew their food, swallow it, and then bring it back up from the stomach in a form called cud. After chewing the cud, they swallow again so the stomach can finish digestion.
In warm climates deer mate at any time of the year. In colder climates they breed in autumn or winter. Female deer give birth to one or two young or, occasionally, to triplets. The offspring nurse for several months. Most deer reach adulthood in one to three years.
Deer and humans
In colonial times the deer of North America were one of the most important wild game animals. Their meat, called venison, was a major food source for early settlers. Deerskin was used to make jackets, moccasins, and other leather goods. White-tailed deer are still the most popular large game animal in the eastern United States.
White-tailed deer are considered nuisances in some areas because there are so many of them. They destroy shrubs and plants and carry ticks that spread Lyme disease. Deer also cause thousands of traffic accidents each year. Some experts believe that hunting is the best way to control white-tailed deer populations.
For some deer species, however, hunting is a serious threat to survival. Another great danger for deer is the loss of their natural homes. People have cleared much of the land where deer lived for farmland and for other purposes. To protect the remaining deer, many places have banned deer hunting and set aside land where deer can live safely.
Scientist
05-12-2007, 13:07
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For 183 million years, during a period of the Earth's history called the Mesozoic era, dinosaurs were the main land animals on Earth. Dinosaurs were so dominant that the Mesozoic era was called the Age of Dinosaurs. Their name comes from the Greek words deinos, meaning “fearfully great,” and sauros, meaning “lizard.” The dinosaurs died out at the end of the Mesozoic era, some 65 million years ago. They were reptiles, but they are believed to be the ancestors of modern birds.
Dinosaur fossils, or remains, were first discovered in the early 19th century. After studying several of these remains a scientist named Richard Owen realized that the bones represented a group of large reptiles that were unlike any living varieties. In a report written in 1841 he called them Dinosauria. Since these early finds, more than 1,000 different sites containing dinosaur fossils have been uncovered around the world.
Where and when dinosaurs lived
The Mesozoic era began about 248 million years ago and ended about 65 million years ago. It was divided into three different periods: the Triassic period (248 to 206 million years ago); the Jurassic period (206 to 144 million years ago); and the Cretaceous period (144 to 65 million years ago). The oldest known dinosaur, the Eoraptor, lived during the Triassic period in what is now South America. (See also geologic time.)
Different species of dinosaurs lived and died out during different periods. For example, some dinosaurs living in the Triassic period did not exist in the Jurassic or Cretaceous periods. Therefore, all species of dinosaurs did not live together at the same time, nor did they all become extinct together. Only a few species of dinosaurs were living on the Earth at the time they all died out.
Dinosaurs were terrestrial, or land, animals that inhabited all parts of the Earth. They adapted to different environments and climates. Their habitat covered a range of ecosystems, including tropical forests and drier desert regions. Fossils of dinosaurs have been found in China, Mongolia, Argentina, the United States, Canada, North Africa, Antarctica, Europe, and India. Fossils are the impressions or remains of a plant or animal of the geologic past, preserved or buried in the Earth's crust.
Physical features
Dinosaurs were a diverse group of creatures that came in all sizes and shapes. They all had hairless bodies like modern-day reptiles, but most dinosaurs were not scaly. For the most part, their skin had a bumpy, pebbly surface, instead of scales. Dinosaurs are often pictured as a dull gray in color, like modern elephants and rhinoceroses. Scientists now believe that dinosaurs may actually have been quite colorful, however. One reason for this belief is that modern birds, which are living relatives of the dinosaurs, can see color. The scientists know that modern animals that can see color are often colorful themselves. The colors help them attract mates since many different species live together and each species needs a unique way to advertise for mates. Because their relatives can see color and are colorful, dinosaurs may have had the same features. Dinosaurs were also not completely cold-blooded, like modern reptiles, nor were they completely warm-blooded. They had their own unique way of controlling their temperature.
Some types of dinosaurs stood upright and walked on their two back legs, while others walked on all fours. Usually, dinosaurs that walked upright on two legs had long, muscular back legs and short front legs. They also had short necks and tails and powerful jaws. Their fingers and toes ended in long, sharp claws. They were built to hunt and eat meat. Dinosaurs that walked on all fours had thick, sturdy legs and elephant-like feet. The necks and tails of some of these dinosaurs were very long. They were built to eat plants.
The skeletons of dinosaurs were quite different, too. Large, four-legged dinosaurs, like Apatosaurus (Brontosaurus), had very heavy bones to support their massive weight. Dinosaurs that walked or ran on two legs usually had hollow bones, like those of modern birds. Some larger species even had large holes in their skulls to make them lighter. Lighter bones helped these dinosaurs to either chase prey or to escape from enemies more quickly.
Generally, dinosaurs are divided into two major groups, or orders: the Ornithischia, or “bird-hipped” dinosaurs, and the Saurischia, or “lizard-hipped” dinosaurs. The way the pelvis is shaped determines the order into which a particular dinosaur fits. Some dinosaurs had a pelvis like that of a modern bird, and some had a pelvis like that of a modern lizard. The Saurischian dinosaurs were further dived into the meat-eating theropods and the plant-eating prosauropods and sauropods. The Ornithischian dinosaurs were plant eaters.
Different species of dinosaurs each had different types of teeth. Some teeth were large and had sawlike edges made for tearing apart flesh. Other teeth were small and flat like molars. These were used for grinding tough plant material.
Dinosaurs varied greatly in size. One of the largest creatures was the Seismosaurus, a plant-eating dinosaur that is believed to have been as long as 140 feet (43 meters). The Compsognathus, a predator that walked on two legs, was probably the smallest at less than 3 feet (1 meter) in length.
Certain dinosaurs had unusual features. Some had horns like a modern rhinoceros. Another dinosaur had a huge club for a tail. Some had bony neck frills or crests on their heads. Still others had large, triangular bony plates sticking out of their backs. (See also Stegosaurus; Triceratops.)
Behavior
Some dinosaurs were solitary animals, living and hunting alone. Some species of dinosaurs lived and roamed in groups. The food habits of dinosaurs are still much discussed among scientists. The size, form, and number of teeth of a particular species give some idea of their diet. The study of fossilized dinosaur droppings, called coprolites, also reveals what dinosaurs ate. Studies show that some species were herbivores, or plant eaters. Others were carnivores, or meat eaters.
Herbivorous dinosaurs usually had a small head and teeth. The smaller species often fed on soft, low-growing plants, such as ferns and horsetails. The tall and long-necked dinosaurs, such as Brachiosaurus, probably fed on high branches and treetops. These types of dinosaurs usually stood and walked on four legs and lived together in groups. They are the most massive of all dinosaurs, and are known as sauropods.
Carnivorous dinosaurs had sharp teeth and sharp, curved claws. They ate mainly smaller, herbivorous dinosaurs. Carnivores normally hunted alone, and they often stalked their prey. Sometimes they hunted in packs to bring down larger dinosaurs. The most ferocious in this group was the predator Tyrannosaurus rex. Some of the carnivorous dinosaurs are thought to have been scavengers that fed mainly on dead animals. These types of dinosaurs usually walked or ran on their two back legs. Carnivorous dinosaurs belonged to the theropod group of the lizard-hipped dinosaurs.
Life cycle
Scientists believe that all dinosaurs reproduced by laying eggs. Some dinosaurs built vast nesting colonies to take care of their young. Baby dinosaurs grew very fast, and many reached adult size in seven or eight years. Dinosaurs exhibited courtship behavior much in the way modern animals do. Rival male dinosaurs may have used their natural weapons, such as horns or spikes, in combat against one another during the breeding season. They also may have used these features as a display to attract females. Scientists have not been able to determine how long individual dinosaurs lived, though they believe that large dinosaurs, like Apatosaurus, could live to be almost 100 years old.
Extinction
The dinosaurs died out at the end of the Cretaceous period, about 65 million years ago. The reasons for their extinction are still debated by scientists. Fossil studies provide some clues to the puzzle. Some scientists believe that dinosaurs died out because of a gradual change in climate. A slow cooling of the earth and a fall in global temperatures may have made survival difficult for these animals. Most scientists now believe, however, that dinosaurs died out suddenly.
One of the possible reasons is that a massive meteorite, asteroid, or comet may have collided with the Earth. The dust thrown up in such a collision may have blocked the light from the sun. This would have resulted in a cold and dark period. The loss of sunlight would have caused plants to die. The herbivores would have then died because they had nothing to eat. Their predators, the carnivores, would also have died as a result. An interesting fact that has puzzled scientists is that some animals survived beyond the period when the dinosaurs disappeared. If a disastrous collision did take place it is not clear why some animals were not hurt by it. The ancestors of such modern animals as frogs, turtles, lizards, and snakes found a way to survive. Birds, which are said to be descendants of dinosaurs, also survived. Perhaps these survivors will give scientists the clues they need to find out what exactly happened to the dinosaurs.
For 183 million years, during a period of the Earth's history called the Mesozoic era, dinosaurs were the main land animals on Earth. Dinosaurs were so dominant that the Mesozoic era was called the Age of Dinosaurs. Their name comes from the Greek words deinos, meaning “fearfully great,” and sauros, meaning “lizard.” The dinosaurs died out at the end of the Mesozoic era, some 65 million years ago. They were reptiles, but they are believed to be the ancestors of modern birds.
Dinosaur fossils, or remains, were first discovered in the early 19th century. After studying several of these remains a scientist named Richard Owen realized that the bones represented a group of large reptiles that were unlike any living varieties. In a report written in 1841 he called them Dinosauria. Since these early finds, more than 1,000 different sites containing dinosaur fossils have been uncovered around the world.
Where and when dinosaurs lived
The Mesozoic era began about 248 million years ago and ended about 65 million years ago. It was divided into three different periods: the Triassic period (248 to 206 million years ago); the Jurassic period (206 to 144 million years ago); and the Cretaceous period (144 to 65 million years ago). The oldest known dinosaur, the Eoraptor, lived during the Triassic period in what is now South America. (See also geologic time.)
Different species of dinosaurs lived and died out during different periods. For example, some dinosaurs living in the Triassic period did not exist in the Jurassic or Cretaceous periods. Therefore, all species of dinosaurs did not live together at the same time, nor did they all become extinct together. Only a few species of dinosaurs were living on the Earth at the time they all died out.
Dinosaurs were terrestrial, or land, animals that inhabited all parts of the Earth. They adapted to different environments and climates. Their habitat covered a range of ecosystems, including tropical forests and drier desert regions. Fossils of dinosaurs have been found in China, Mongolia, Argentina, the United States, Canada, North Africa, Antarctica, Europe, and India. Fossils are the impressions or remains of a plant or animal of the geologic past, preserved or buried in the Earth's crust.
Physical features
Dinosaurs were a diverse group of creatures that came in all sizes and shapes. They all had hairless bodies like modern-day reptiles, but most dinosaurs were not scaly. For the most part, their skin had a bumpy, pebbly surface, instead of scales. Dinosaurs are often pictured as a dull gray in color, like modern elephants and rhinoceroses. Scientists now believe that dinosaurs may actually have been quite colorful, however. One reason for this belief is that modern birds, which are living relatives of the dinosaurs, can see color. The scientists know that modern animals that can see color are often colorful themselves. The colors help them attract mates since many different species live together and each species needs a unique way to advertise for mates. Because their relatives can see color and are colorful, dinosaurs may have had the same features. Dinosaurs were also not completely cold-blooded, like modern reptiles, nor were they completely warm-blooded. They had their own unique way of controlling their temperature.
Some types of dinosaurs stood upright and walked on their two back legs, while others walked on all fours. Usually, dinosaurs that walked upright on two legs had long, muscular back legs and short front legs. They also had short necks and tails and powerful jaws. Their fingers and toes ended in long, sharp claws. They were built to hunt and eat meat. Dinosaurs that walked on all fours had thick, sturdy legs and elephant-like feet. The necks and tails of some of these dinosaurs were very long. They were built to eat plants.
The skeletons of dinosaurs were quite different, too. Large, four-legged dinosaurs, like Apatosaurus (Brontosaurus), had very heavy bones to support their massive weight. Dinosaurs that walked or ran on two legs usually had hollow bones, like those of modern birds. Some larger species even had large holes in their skulls to make them lighter. Lighter bones helped these dinosaurs to either chase prey or to escape from enemies more quickly.
Generally, dinosaurs are divided into two major groups, or orders: the Ornithischia, or “bird-hipped” dinosaurs, and the Saurischia, or “lizard-hipped” dinosaurs. The way the pelvis is shaped determines the order into which a particular dinosaur fits. Some dinosaurs had a pelvis like that of a modern bird, and some had a pelvis like that of a modern lizard. The Saurischian dinosaurs were further dived into the meat-eating theropods and the plant-eating prosauropods and sauropods. The Ornithischian dinosaurs were plant eaters.
Different species of dinosaurs each had different types of teeth. Some teeth were large and had sawlike edges made for tearing apart flesh. Other teeth were small and flat like molars. These were used for grinding tough plant material.
Dinosaurs varied greatly in size. One of the largest creatures was the Seismosaurus, a plant-eating dinosaur that is believed to have been as long as 140 feet (43 meters). The Compsognathus, a predator that walked on two legs, was probably the smallest at less than 3 feet (1 meter) in length.
Certain dinosaurs had unusual features. Some had horns like a modern rhinoceros. Another dinosaur had a huge club for a tail. Some had bony neck frills or crests on their heads. Still others had large, triangular bony plates sticking out of their backs. (See also Stegosaurus; Triceratops.)
Behavior
Some dinosaurs were solitary animals, living and hunting alone. Some species of dinosaurs lived and roamed in groups. The food habits of dinosaurs are still much discussed among scientists. The size, form, and number of teeth of a particular species give some idea of their diet. The study of fossilized dinosaur droppings, called coprolites, also reveals what dinosaurs ate. Studies show that some species were herbivores, or plant eaters. Others were carnivores, or meat eaters.
Herbivorous dinosaurs usually had a small head and teeth. The smaller species often fed on soft, low-growing plants, such as ferns and horsetails. The tall and long-necked dinosaurs, such as Brachiosaurus, probably fed on high branches and treetops. These types of dinosaurs usually stood and walked on four legs and lived together in groups. They are the most massive of all dinosaurs, and are known as sauropods.
Carnivorous dinosaurs had sharp teeth and sharp, curved claws. They ate mainly smaller, herbivorous dinosaurs. Carnivores normally hunted alone, and they often stalked their prey. Sometimes they hunted in packs to bring down larger dinosaurs. The most ferocious in this group was the predator Tyrannosaurus rex. Some of the carnivorous dinosaurs are thought to have been scavengers that fed mainly on dead animals. These types of dinosaurs usually walked or ran on their two back legs. Carnivorous dinosaurs belonged to the theropod group of the lizard-hipped dinosaurs.
Life cycle
Scientists believe that all dinosaurs reproduced by laying eggs. Some dinosaurs built vast nesting colonies to take care of their young. Baby dinosaurs grew very fast, and many reached adult size in seven or eight years. Dinosaurs exhibited courtship behavior much in the way modern animals do. Rival male dinosaurs may have used their natural weapons, such as horns or spikes, in combat against one another during the breeding season. They also may have used these features as a display to attract females. Scientists have not been able to determine how long individual dinosaurs lived, though they believe that large dinosaurs, like Apatosaurus, could live to be almost 100 years old.
Extinction
The dinosaurs died out at the end of the Cretaceous period, about 65 million years ago. The reasons for their extinction are still debated by scientists. Fossil studies provide some clues to the puzzle. Some scientists believe that dinosaurs died out because of a gradual change in climate. A slow cooling of the earth and a fall in global temperatures may have made survival difficult for these animals. Most scientists now believe, however, that dinosaurs died out suddenly.
One of the possible reasons is that a massive meteorite, asteroid, or comet may have collided with the Earth. The dust thrown up in such a collision may have blocked the light from the sun. This would have resulted in a cold and dark period. The loss of sunlight would have caused plants to die. The herbivores would have then died because they had nothing to eat. Their predators, the carnivores, would also have died as a result. An interesting fact that has puzzled scientists is that some animals survived beyond the period when the dinosaurs disappeared. If a disastrous collision did take place it is not clear why some animals were not hurt by it. The ancestors of such modern animals as frogs, turtles, lizards, and snakes found a way to survive. Birds, which are said to be descendants of dinosaurs, also survived. Perhaps these survivors will give scientists the clues they need to find out what exactly happened to the dinosaurs.
Scientist
21-01-2008, 07:37
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The most commonly displayed dinosaur in museums is Diplodocus. This dinosaur was longer than a tennis court and is the longest complete dinosaur that scientists have discovered. The name Diplodocus means “double beam.” This name comes from a special feature of its tail bones. Diplodocus belongs to a group of enormous dinosaurs called sauropods. The sauropods were large, plant-eating dinosaurs with long necks, massive bodies, and four pillarlike legs to support the body.
Where and when Diplodocus lived
Diplodocus lived about 159 to 144 million years ago during a period of the Earth's history called the Jurassic. Remains of this dinosaur have been found in North America, especially in Colorado, Montana, Utah, and Wyoming. Diplodocus lived in meadows where plants grew thick and at the edges of forests and other areas where many trees grew.
Physical features
Scientists refer to Diplodocus as a walking suspension bridge. Its four legs were built like supporting pillars, and its spine held up its body, just as a bridge with cables holds up a road. Diplodocus measured up to 90 feet (27 meters) long and stood about 15 feet (4.6 meters) tall at the hips. A lightweight among the sauropod dinosaurs, Diplodocus weighed only about 30 tons. The unique, hollow structure of its backbones helped this animal to be so light. It had a long neck and a very long tail. Diplodocus had a small, horselike head and a very small brain. It had peg-shaped teeth in the front of its mouth. Its back legs were slightly longer than its front legs, making the animal slope downward from its hips to its head. Diplodocus had elephantlike feet with three claws on each back foot. One section of its tail bones featured a pair of anvil-shaped projections on the underside of each bone in that section. Scientists believe that these bones served as protection for the blood vessels and tissues of the tail. These are the “double beams” for which the dinosaur is named. Scientists once thought that Diplodocus dragged its tail along the ground. They now agree that this dinosaur held its tail high off the ground. It may have used its tail as a whip in self-defense.
Behavior
Diplodocus was a plant eater. It may have fed on low-lying ferns, though its long neck also allowed it to browse the tops of trees. Some scientists think that Diplodocus actually stood up on its back legs to reach the treetops. Its specially designed tail with the “double beam” bones may have acted as an extra leg for the animal to lean back on. Diplodocus had no back teeth to chew with, so it swallowed small stones to help grind up the plants in its stomach. Diplodocus lived and traveled in herds. It reproduced by laying eggs.
The most commonly displayed dinosaur in museums is Diplodocus. This dinosaur was longer than a tennis court and is the longest complete dinosaur that scientists have discovered. The name Diplodocus means “double beam.” This name comes from a special feature of its tail bones. Diplodocus belongs to a group of enormous dinosaurs called sauropods. The sauropods were large, plant-eating dinosaurs with long necks, massive bodies, and four pillarlike legs to support the body.
Where and when Diplodocus lived
Diplodocus lived about 159 to 144 million years ago during a period of the Earth's history called the Jurassic. Remains of this dinosaur have been found in North America, especially in Colorado, Montana, Utah, and Wyoming. Diplodocus lived in meadows where plants grew thick and at the edges of forests and other areas where many trees grew.
Physical features
Scientists refer to Diplodocus as a walking suspension bridge. Its four legs were built like supporting pillars, and its spine held up its body, just as a bridge with cables holds up a road. Diplodocus measured up to 90 feet (27 meters) long and stood about 15 feet (4.6 meters) tall at the hips. A lightweight among the sauropod dinosaurs, Diplodocus weighed only about 30 tons. The unique, hollow structure of its backbones helped this animal to be so light. It had a long neck and a very long tail. Diplodocus had a small, horselike head and a very small brain. It had peg-shaped teeth in the front of its mouth. Its back legs were slightly longer than its front legs, making the animal slope downward from its hips to its head. Diplodocus had elephantlike feet with three claws on each back foot. One section of its tail bones featured a pair of anvil-shaped projections on the underside of each bone in that section. Scientists believe that these bones served as protection for the blood vessels and tissues of the tail. These are the “double beams” for which the dinosaur is named. Scientists once thought that Diplodocus dragged its tail along the ground. They now agree that this dinosaur held its tail high off the ground. It may have used its tail as a whip in self-defense.
Behavior
Diplodocus was a plant eater. It may have fed on low-lying ferns, though its long neck also allowed it to browse the tops of trees. Some scientists think that Diplodocus actually stood up on its back legs to reach the treetops. Its specially designed tail with the “double beam” bones may have acted as an extra leg for the animal to lean back on. Diplodocus had no back teeth to chew with, so it swallowed small stones to help grind up the plants in its stomach. Diplodocus lived and traveled in herds. It reproduced by laying eggs.
Scientist
21-01-2008, 07:44
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The dog is one of the most popular animals in the world. It was among the first animals to be domesticated, or trained for use by humans. It is characterized by loyalty, friendship, protectiveness, and affection. Therefore, dogs are also known as man's best friend.
Physical characteristics
Domestic dogs vary in size depending on their breeds. A small Mexican Chihuahua can weigh just over 1 pound (around 500 grams), whereas the Great Dane can weigh as much as 130 pounds (60 kilograms). Dogs grow to various heights. The Irish wolfhound stands about 32 inches (81 centimeters) high at the top of its shoulders. The chihuahua stands about 5 inches (12 centimeters) high.
Dogs, like humans, have five senses. Their sense of smell is very sharp. A dog continually sniffs the air, the ground, and nearby objects to learn what is happening around it. Some breeds, such as the German shepherd and the bloodhound, have a much sharper sense of smell than others. Because of this, these breeds are used to track explosives, drugs, and missing persons. Dogs also have a fine sense of hearing. They can detect noises well beyond what people can hear.
The eyesight of a dog is not as keen as its sense of smell. It is generally thought that dogs are poor at identifying color differences. Dogs can generally see better in dim light than humans but not as well in bright light. They have a wider range of vision than humans because their eyes are set further toward the sides of their heads. However, dogs are not as good at focusing on objects at close range or at judging distances.
The dog's foot, or paw, has five toes. One of them, the dewclaw, is too high to be of any use. A toenail, or claw, emerges from the end of each toe. The foot also has cushiony pads for each toe and two larger pads farther up the paw.
The thin tongue of the dog is used mainly for guiding food to the throat, for licking the coat clean, and for perspiration. When a dog is overheated, it cools off by hanging its tongue out and panting. As it pants, the perspiration evaporates from its tongue and cools the animal. The dog also sweats through the pads on its paws and slightly through its skin.
Behavior
The dog is a social creature. It prefers the company of people and of other dogs. Therefore, it is considered to be a pack animal. Dogs claim territory and mark it as its own. Dogs indicate their area by urinating and rubbing their scent on the ground or on trees as a sign of their presence.
Dogs are capable of a wide range of responses to their environment. For example, when a dog meets another dog and its ears are erect, it is concentrating on the other dog. If its ears are pointing forward, it is on the alert. If a dog holds its tail high and wags it, the animal is happy and confident. If it drops its tail and remains still, the dog is anxious. If it pulls its tail between its legs, the dog is afraid. If on meeting a person or another dog it pulls back its lips and growls, it is making a threat.
Breeds
It is estimated that there are about 400 purebred dogs worldwide. For a puppy to be purebred, father and mother must be of the same breed. A mongrel dog is one with many breeds in its background.
Throughout the years, dogs have been bred for the purposes of hunting, herding, and guarding. Dogs such as the Doberman pinscher and the German shepherd serve as alert and aggressive watchdogs. Others, such as the beagle and the cocker spaniel, are playful family pets, even though they were originally bred for hunting. Some others, such as the collie and the Welsh corgi, can herd farm animals.
The American Kennel Club recognizes seven groups according to their original functions. These groups are sporting dogs, hounds, working dogs, terriers, toys, non-sporting dogs, and herding dogs. Sporting dogs hunt, locate, and retrieve game birds. Hounds hunt all game except birds. Working dogs can do jobs such as water rescues, pulling sleds and carts, and guarding life and property. Herding dogs control the movement of other animals. Terriers were once bred to hunt rodents but are now bred as house pets. Toys are tiny dogs bred mainly as pets. Non-sporting dogs are those purebreds that do not fit in the other categories.
Of the wild dogs one of the most important is the dingo, found in Australia. However, dingoes are rarely seen outside of zoos. Efforts are being made to protect them in the wild. Another, the dhole of India, is said to be a fierce, untamable dog.
Life cycle
The puppy grows inside the mother for 63 days before its birth. Puppies are born blind and deaf. They are totally dependent on the mother for warmth and nourishment. Between 10 and 14 days after birth, their eyes and ear canals open. The puppies then begin to move around actively. As they grow, they become more curious and start to investigate their surroundings. Between 12 and 16 weeks, the puppy becomes independent of its mother and starts exploring new territories.
The average life span of a small- and a medium-sized dog is 15 years. A large dog lives only up to the age of 10.
Dogs and humans
Dogs have been with humans since prehistoric times. Over the years they have performed various services. Dogs have also served as a source of food. In the past, dogs have even been worshiped as gods.
The ancient Romans relied on watchdogs. So many dogs were kept in the larger Roman cities that any house with a watchdog was required to have a warning sign, “Cave Canem,” or Beware of the Dog. The Romans also used dogs for military purposes, sometimes as attack dogs and sometimes as messengers.
Toy dogs were popular among the ancient Chinese. The little animals were used to provide warmth when carried in the wide sleeves of the gowns.
Recently, dogs have been used in drug research and scientific experimentation. Soviet scientists launched dogs into space to test the ability of mammals to survive there. Specially trained dogs serve as the “eyes” of the blind, guiding the steps of their sightless masters around obstacles and hazards.
The dog is one of the most popular animals in the world. It was among the first animals to be domesticated, or trained for use by humans. It is characterized by loyalty, friendship, protectiveness, and affection. Therefore, dogs are also known as man's best friend.
Physical characteristics
Domestic dogs vary in size depending on their breeds. A small Mexican Chihuahua can weigh just over 1 pound (around 500 grams), whereas the Great Dane can weigh as much as 130 pounds (60 kilograms). Dogs grow to various heights. The Irish wolfhound stands about 32 inches (81 centimeters) high at the top of its shoulders. The chihuahua stands about 5 inches (12 centimeters) high.
Dogs, like humans, have five senses. Their sense of smell is very sharp. A dog continually sniffs the air, the ground, and nearby objects to learn what is happening around it. Some breeds, such as the German shepherd and the bloodhound, have a much sharper sense of smell than others. Because of this, these breeds are used to track explosives, drugs, and missing persons. Dogs also have a fine sense of hearing. They can detect noises well beyond what people can hear.
The eyesight of a dog is not as keen as its sense of smell. It is generally thought that dogs are poor at identifying color differences. Dogs can generally see better in dim light than humans but not as well in bright light. They have a wider range of vision than humans because their eyes are set further toward the sides of their heads. However, dogs are not as good at focusing on objects at close range or at judging distances.
The dog's foot, or paw, has five toes. One of them, the dewclaw, is too high to be of any use. A toenail, or claw, emerges from the end of each toe. The foot also has cushiony pads for each toe and two larger pads farther up the paw.
The thin tongue of the dog is used mainly for guiding food to the throat, for licking the coat clean, and for perspiration. When a dog is overheated, it cools off by hanging its tongue out and panting. As it pants, the perspiration evaporates from its tongue and cools the animal. The dog also sweats through the pads on its paws and slightly through its skin.
Behavior
The dog is a social creature. It prefers the company of people and of other dogs. Therefore, it is considered to be a pack animal. Dogs claim territory and mark it as its own. Dogs indicate their area by urinating and rubbing their scent on the ground or on trees as a sign of their presence.
Dogs are capable of a wide range of responses to their environment. For example, when a dog meets another dog and its ears are erect, it is concentrating on the other dog. If its ears are pointing forward, it is on the alert. If a dog holds its tail high and wags it, the animal is happy and confident. If it drops its tail and remains still, the dog is anxious. If it pulls its tail between its legs, the dog is afraid. If on meeting a person or another dog it pulls back its lips and growls, it is making a threat.
Breeds
It is estimated that there are about 400 purebred dogs worldwide. For a puppy to be purebred, father and mother must be of the same breed. A mongrel dog is one with many breeds in its background.
Throughout the years, dogs have been bred for the purposes of hunting, herding, and guarding. Dogs such as the Doberman pinscher and the German shepherd serve as alert and aggressive watchdogs. Others, such as the beagle and the cocker spaniel, are playful family pets, even though they were originally bred for hunting. Some others, such as the collie and the Welsh corgi, can herd farm animals.
The American Kennel Club recognizes seven groups according to their original functions. These groups are sporting dogs, hounds, working dogs, terriers, toys, non-sporting dogs, and herding dogs. Sporting dogs hunt, locate, and retrieve game birds. Hounds hunt all game except birds. Working dogs can do jobs such as water rescues, pulling sleds and carts, and guarding life and property. Herding dogs control the movement of other animals. Terriers were once bred to hunt rodents but are now bred as house pets. Toys are tiny dogs bred mainly as pets. Non-sporting dogs are those purebreds that do not fit in the other categories.
Of the wild dogs one of the most important is the dingo, found in Australia. However, dingoes are rarely seen outside of zoos. Efforts are being made to protect them in the wild. Another, the dhole of India, is said to be a fierce, untamable dog.
Life cycle
The puppy grows inside the mother for 63 days before its birth. Puppies are born blind and deaf. They are totally dependent on the mother for warmth and nourishment. Between 10 and 14 days after birth, their eyes and ear canals open. The puppies then begin to move around actively. As they grow, they become more curious and start to investigate their surroundings. Between 12 and 16 weeks, the puppy becomes independent of its mother and starts exploring new territories.
The average life span of a small- and a medium-sized dog is 15 years. A large dog lives only up to the age of 10.
Dogs and humans
Dogs have been with humans since prehistoric times. Over the years they have performed various services. Dogs have also served as a source of food. In the past, dogs have even been worshiped as gods.
The ancient Romans relied on watchdogs. So many dogs were kept in the larger Roman cities that any house with a watchdog was required to have a warning sign, “Cave Canem,” or Beware of the Dog. The Romans also used dogs for military purposes, sometimes as attack dogs and sometimes as messengers.
Toy dogs were popular among the ancient Chinese. The little animals were used to provide warmth when carried in the wide sleeves of the gowns.
Recently, dogs have been used in drug research and scientific experimentation. Soviet scientists launched dogs into space to test the ability of mammals to survive there. Specially trained dogs serve as the “eyes” of the blind, guiding the steps of their sightless masters around obstacles and hazards.
Scientist
21-01-2008, 07:48
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
Known for their intelligence, playfulness, and friendliness toward humans, dolphins can often be seen swimming alongside boats or performing at aquariums. Dolphins look like large fish, but they are actually small whales. Like whales and other mammals, they breathe through lungs instead of gills and give birth to live young, among other typical traits.
Dolphins are closely related to another group of small whales, the porpoises. Because dolphins and porpoises look so much alike, the two are often confused with one another. In fact, the names dolphin and porpoise are sometimes used as if they are one and the same. In general, however, dolphins can be told apart from porpoises by their larger size and their snouts. A dolphin has a long, sharp snout that is flattened like a beak. A porpoise's snout is short and blunt (see porpoise). The name dolphin is also sometimes used for a large fish known as the mahimahi or dorado. As a fish, the mahimahi differs from the mammals more commonly thought of as dolphins.
Where dolphins live
Dolphins can be found throughout the world in either salt water or freshwater. The most widespread species, or kinds, are the common and bottle-nosed dolphins. Both live in warm and temperate oceans and seas worldwide. River dolphins are found only in South America and Asia. They prefer freshwater.
Physical features
The larger dolphins, including the bottle-nosed species, can reach a length of 13 feet (4 meters). Most dolphins, however, are 7 to 10 feet (2 to 3 meters) long. They have smooth, rubbery skin and are usually colored in some mixture of black, white, and gray. A layer of fat beneath the skin, known as blubber, helps keep them warm in the water. Dolphins have two flippers, which are fins that serve as forelimbs, as well as a triangular fin on the back.
Like other mammals, dolphins are warm-blooded. This means that they keep their body temperature about the same even when the temperature of their surroundings changes. Because a dolphin breathes through lungs, it must come up to the water's surface to breathe. A single nostril, called a blowhole, on the top of a dolphin's head lets air move in and out.
Behavior
Dolphins are social animals, meaning that they generally live in schools, or groups. Sometimes these schools are made up of as many as 1,000 individuals. Dolphins use a range of sounds to communicate with each other and often act together to achieve a goal, such as trapping fish to eat. They have been known to help an injured dolphin by pushing it to the surface so it can breathe.
Dolphins also use sounds to find objects underwater. A dolphin lets out whistles and squeaks that are too high-pitched to be heard by humans. These sounds reflect off solid surfaces and then travel back to the dolphin's sensitive ears. The time it takes for a reflected sound to return tells the dolphin how far away something is. This process is called echolocation. It is especially helpful for river dolphins, many of which live in muddy water.
Dolphins are intelligent animals with great learning abilities. They have been trained to perform impressive tricks in aquariums, including high leaps above the water. Their speedy and graceful swimming adds to their appeal as performers.
Reproduction in dolphins usually takes place in the warm months. After a pregnancy of about 10–12 months, a female dolphin gives birth to a single offspring. A newborn dolphin, called a calf, looks like a smaller version of its parents. Just after birth the mother nudges the calf toward the surface of the water so that it can take its first breath of air. Dolphin mothers provide milk for their young for a year or longer. The length of time a dolphin lives varies by species, but some have survived more than 30 years.
Survival issues
Bottle-nosed dolphins and other species used to be hunted in large numbers for their meat and for other reasons. Many countries have banned dolphin hunting, but the practice continues in some places. Nets set in the ocean to catch tuna and other fish are another threat to dolphins. Dolphins swim into these nets and become trapped. To prevent dolphins from being injured or drowning in the nets, some of them are now made with exits that allow dolphins, but not fish, to escape. Another danger is pollution of the world's oceans. The dumping of chemicals and other wastes into the water may poison the dolphins' food supply and make the dolphins sick.
Known for their intelligence, playfulness, and friendliness toward humans, dolphins can often be seen swimming alongside boats or performing at aquariums. Dolphins look like large fish, but they are actually small whales. Like whales and other mammals, they breathe through lungs instead of gills and give birth to live young, among other typical traits.
Dolphins are closely related to another group of small whales, the porpoises. Because dolphins and porpoises look so much alike, the two are often confused with one another. In fact, the names dolphin and porpoise are sometimes used as if they are one and the same. In general, however, dolphins can be told apart from porpoises by their larger size and their snouts. A dolphin has a long, sharp snout that is flattened like a beak. A porpoise's snout is short and blunt (see porpoise). The name dolphin is also sometimes used for a large fish known as the mahimahi or dorado. As a fish, the mahimahi differs from the mammals more commonly thought of as dolphins.
Where dolphins live
Dolphins can be found throughout the world in either salt water or freshwater. The most widespread species, or kinds, are the common and bottle-nosed dolphins. Both live in warm and temperate oceans and seas worldwide. River dolphins are found only in South America and Asia. They prefer freshwater.
Physical features
The larger dolphins, including the bottle-nosed species, can reach a length of 13 feet (4 meters). Most dolphins, however, are 7 to 10 feet (2 to 3 meters) long. They have smooth, rubbery skin and are usually colored in some mixture of black, white, and gray. A layer of fat beneath the skin, known as blubber, helps keep them warm in the water. Dolphins have two flippers, which are fins that serve as forelimbs, as well as a triangular fin on the back.
Like other mammals, dolphins are warm-blooded. This means that they keep their body temperature about the same even when the temperature of their surroundings changes. Because a dolphin breathes through lungs, it must come up to the water's surface to breathe. A single nostril, called a blowhole, on the top of a dolphin's head lets air move in and out.
Behavior
Dolphins are social animals, meaning that they generally live in schools, or groups. Sometimes these schools are made up of as many as 1,000 individuals. Dolphins use a range of sounds to communicate with each other and often act together to achieve a goal, such as trapping fish to eat. They have been known to help an injured dolphin by pushing it to the surface so it can breathe.
Dolphins also use sounds to find objects underwater. A dolphin lets out whistles and squeaks that are too high-pitched to be heard by humans. These sounds reflect off solid surfaces and then travel back to the dolphin's sensitive ears. The time it takes for a reflected sound to return tells the dolphin how far away something is. This process is called echolocation. It is especially helpful for river dolphins, many of which live in muddy water.
Dolphins are intelligent animals with great learning abilities. They have been trained to perform impressive tricks in aquariums, including high leaps above the water. Their speedy and graceful swimming adds to their appeal as performers.
Reproduction in dolphins usually takes place in the warm months. After a pregnancy of about 10–12 months, a female dolphin gives birth to a single offspring. A newborn dolphin, called a calf, looks like a smaller version of its parents. Just after birth the mother nudges the calf toward the surface of the water so that it can take its first breath of air. Dolphin mothers provide milk for their young for a year or longer. The length of time a dolphin lives varies by species, but some have survived more than 30 years.
Survival issues
Bottle-nosed dolphins and other species used to be hunted in large numbers for their meat and for other reasons. Many countries have banned dolphin hunting, but the practice continues in some places. Nets set in the ocean to catch tuna and other fish are another threat to dolphins. Dolphins swim into these nets and become trapped. To prevent dolphins from being injured or drowning in the nets, some of them are now made with exits that allow dolphins, but not fish, to escape. Another danger is pollution of the world's oceans. The dumping of chemicals and other wastes into the water may poison the dolphins' food supply and make the dolphins sick.
Scientist
21-01-2008, 07:52
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
A descendant of the African wild ass, the donkey belongs to the horse family. The words donkey and ass are used to identify the same animal. However, the term ass is more often used when the animal is wild, and the term donkey is used when the animal is domesticated, or tamed so that it is useful for humans.
Where donkeys live
The donkey is believed to be originally from Southern and Central Asia, but it is now used as a working animal around the world. For example, donkeys are used in the mountains of Ethiopia and other parts of Northeast Africa, the high plains of Tibet, and the dry regions of Mongolia.
Physical features
The average donkey stands 40 inches (102 centimeters) at the shoulder, but different breeds vary greatly in size and shape. The Sicilian donkey reaches only about 24 inches (61 centimeters), while the large ass of Majorca stands at about 62 inches (158 centimeters). The American ass can reach a height of about 66 inches (168 centimeters). Donkeys range from white to gray or black in color. They usually have a dark stripe from the mane to the tail and a crosswise stripe on the shoulders. The mane is short and upright and the tail has long hair only at the end. The very long ears are dark at the base and tip.
Although the names donkey and burro can be used to mean the same thing, the term burro is widely used in the southwestern United States to describe small donkeys. Burro is the word for donkey in Spanish.
Behavior
The donkey usually feeds on coarse food. It is a patient and hardworking animal. The donkey responds to gentle treatment with affection and shows attachment to its master. Although considered stubborn and slow, a donkey can carry heavy loads over rough land. The donkey can handle the uneven ground of the mountains better than a horse can.
The male donkey, also called a jack, can be mated with a mare (female horse) to produce the sturdy mule. The female donkey, or jennet, can be mated with a stallion (male horse) to produce the hinny. Mules and hinnies cannot reproduce. The mule is used for farm work and as a baggage animal for carrying equipment on expeditions. In subtropical and tropical countries mules are used because of their ability to withstand heat and irregular feeding.
A descendant of the African wild ass, the donkey belongs to the horse family. The words donkey and ass are used to identify the same animal. However, the term ass is more often used when the animal is wild, and the term donkey is used when the animal is domesticated, or tamed so that it is useful for humans.
Where donkeys live
The donkey is believed to be originally from Southern and Central Asia, but it is now used as a working animal around the world. For example, donkeys are used in the mountains of Ethiopia and other parts of Northeast Africa, the high plains of Tibet, and the dry regions of Mongolia.
Physical features
The average donkey stands 40 inches (102 centimeters) at the shoulder, but different breeds vary greatly in size and shape. The Sicilian donkey reaches only about 24 inches (61 centimeters), while the large ass of Majorca stands at about 62 inches (158 centimeters). The American ass can reach a height of about 66 inches (168 centimeters). Donkeys range from white to gray or black in color. They usually have a dark stripe from the mane to the tail and a crosswise stripe on the shoulders. The mane is short and upright and the tail has long hair only at the end. The very long ears are dark at the base and tip.
Although the names donkey and burro can be used to mean the same thing, the term burro is widely used in the southwestern United States to describe small donkeys. Burro is the word for donkey in Spanish.
Behavior
The donkey usually feeds on coarse food. It is a patient and hardworking animal. The donkey responds to gentle treatment with affection and shows attachment to its master. Although considered stubborn and slow, a donkey can carry heavy loads over rough land. The donkey can handle the uneven ground of the mountains better than a horse can.
The male donkey, also called a jack, can be mated with a mare (female horse) to produce the sturdy mule. The female donkey, or jennet, can be mated with a stallion (male horse) to produce the hinny. Mules and hinnies cannot reproduce. The mule is used for farm work and as a baggage animal for carrying equipment on expeditions. In subtropical and tropical countries mules are used because of their ability to withstand heat and irregular feeding.
Scientist
21-01-2008, 07:56
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
In the wild or raised by people, ducks are familiar birds around the world. About 40 species, or types, live in North America alone. Ducks, geese, and swans are known as waterfowl in North America and wildfowl in Europe. Ducks are the smallest of the waterfowl.
Where ducks live
Ducks live on the water or close to it. They are found on and around all continents except Antarctica. There are freshwater ducks and saltwater ducks, ducks of coastal waters and ducks of the open sea. Many ducks are migratory, meaning that they travel long distances for different seasons. Northern ducks, for example, fly south for the winter.
Physical features
Ducks are like geese and swans in many ways. All three kinds of waterfowl have large bills and webbed feet. Their bodies are protected from cold by soft inner feathers called down. Their outer feathers are protected from water by oil that comes from a gland near the tail. But ducks are smaller than the other waterfowl, and they have shorter necks in proportion to their bodies. The legs of ducks are positioned to move the bird smoothly through water, which is why ducks waddle comically on land.
Ducks vary in size and color. The familiar mallard of North America, Europe, and Asia is about 24 inches (61 centimeters) long, including the tail. Mallards usually weigh less than 3 pounds (1.4 kilograms). Male ducks, known as drakes, are often much more colorful than the females. The males of the wood duck and mandarin duck species have especially splendid feathers.
Behavior
Ducks can be grouped according to their feeding and nesting behavior. Those that feed by dipping the head below the surface while tipping up the tail are called dabbling ducks. Dabbling ducks live in marshes, shallow ponds, and slow-moving streams. They feed on the water plants, shellfish, and insects that they find in the shallows. Some of them also feed on land. The mallard is the best known of the dabbling ducks. The black duck of North America and the teals, wigeons, pintails, and shovelers are also dabbling ducks. Dabbling ducks that nest in trees are called perching ducks. The wood duck of North America, the mandarin duck of China, and the big muscovy duck of South America are perching ducks.
Ducks that dive far below the surface are known as diving ducks. Some diving ducks are sea ducks. These ducks feed mostly on fish and sometimes sleep on the water. Mergansers, scoters, goldeneyes, and eiders are among the sea ducks. Other diving ducks stay close to the shore and are called bay ducks, or pochards. The canvasback is a bay duck that eats mostly water plants. Other bay ducks, such as the scaup, prefer shellfish. Not all diving ducks are saltwater birds. The stifftail group includes many freshwater divers. The ruddy duck is the most familiar North American stifftail.
Dabbling ducks nest mostly in northern regions and fly south in autumn. They are fast fliers. By contrast, some of the diving ducks of South America cannot fly at all. They are called steamer ducks because they run on the water with their wings churning like the paddles of old-fashioned steamboats. Other diving ducks, such as the ruddy duck, find it almost impossible to walk on land.
Life cycle
Most ducks make their nests on the ground, near water. They use plants, grass, and down from their own bodies to line the nest. Once the eggs are laid, the drake has nothing more to do with raising the family. The female tends the 6 to 12 eggs, keeping them covered with down while she is away from the nest. The eggs hatch into fluffy ducklings in about 20 to 25 days.
The ducklings can feed themselves and swim soon after birth. Within a day or so, their mother leads them to the water in a little parade. She stays close to the ducklings and protects them until their flight feathers grow in. By the time the young ducks make their first long flight to their wintering grounds, they are completely on their own.
The parents and other adults lose their flight feathers as their breeding season ends. For a few weeks afterward they are unable to fly. At this time drakes usually grow a duller coat of feathers, which they keep for a few months before the more colorful feathers grow back in at breeding time. Ducks kept by people have lived 20 years, but the average life span in the wild is much shorter.
Ducks and people
Ducks have been domesticated—kept and bred by humans—for thousands of years. Many people value ducks for the meat, eggs, and down they provide. The down is used to make warm clothing and bedding.
The duck is a popular game animal. Largely because of hunting, the Labrador duck became extinct in the late 1800s, and other ducks are now rare. Governments in some countries now keep track of wild ducks and control hunting. People who want to hunt waterfowl in the United States are required to buy a special stamp. Some of the money the government gets from selling the stamp is used to maintain breeding habitats.
In the wild or raised by people, ducks are familiar birds around the world. About 40 species, or types, live in North America alone. Ducks, geese, and swans are known as waterfowl in North America and wildfowl in Europe. Ducks are the smallest of the waterfowl.
Where ducks live
Ducks live on the water or close to it. They are found on and around all continents except Antarctica. There are freshwater ducks and saltwater ducks, ducks of coastal waters and ducks of the open sea. Many ducks are migratory, meaning that they travel long distances for different seasons. Northern ducks, for example, fly south for the winter.
Physical features
Ducks are like geese and swans in many ways. All three kinds of waterfowl have large bills and webbed feet. Their bodies are protected from cold by soft inner feathers called down. Their outer feathers are protected from water by oil that comes from a gland near the tail. But ducks are smaller than the other waterfowl, and they have shorter necks in proportion to their bodies. The legs of ducks are positioned to move the bird smoothly through water, which is why ducks waddle comically on land.
Ducks vary in size and color. The familiar mallard of North America, Europe, and Asia is about 24 inches (61 centimeters) long, including the tail. Mallards usually weigh less than 3 pounds (1.4 kilograms). Male ducks, known as drakes, are often much more colorful than the females. The males of the wood duck and mandarin duck species have especially splendid feathers.
Behavior
Ducks can be grouped according to their feeding and nesting behavior. Those that feed by dipping the head below the surface while tipping up the tail are called dabbling ducks. Dabbling ducks live in marshes, shallow ponds, and slow-moving streams. They feed on the water plants, shellfish, and insects that they find in the shallows. Some of them also feed on land. The mallard is the best known of the dabbling ducks. The black duck of North America and the teals, wigeons, pintails, and shovelers are also dabbling ducks. Dabbling ducks that nest in trees are called perching ducks. The wood duck of North America, the mandarin duck of China, and the big muscovy duck of South America are perching ducks.
Ducks that dive far below the surface are known as diving ducks. Some diving ducks are sea ducks. These ducks feed mostly on fish and sometimes sleep on the water. Mergansers, scoters, goldeneyes, and eiders are among the sea ducks. Other diving ducks stay close to the shore and are called bay ducks, or pochards. The canvasback is a bay duck that eats mostly water plants. Other bay ducks, such as the scaup, prefer shellfish. Not all diving ducks are saltwater birds. The stifftail group includes many freshwater divers. The ruddy duck is the most familiar North American stifftail.
Dabbling ducks nest mostly in northern regions and fly south in autumn. They are fast fliers. By contrast, some of the diving ducks of South America cannot fly at all. They are called steamer ducks because they run on the water with their wings churning like the paddles of old-fashioned steamboats. Other diving ducks, such as the ruddy duck, find it almost impossible to walk on land.
Life cycle
Most ducks make their nests on the ground, near water. They use plants, grass, and down from their own bodies to line the nest. Once the eggs are laid, the drake has nothing more to do with raising the family. The female tends the 6 to 12 eggs, keeping them covered with down while she is away from the nest. The eggs hatch into fluffy ducklings in about 20 to 25 days.
The ducklings can feed themselves and swim soon after birth. Within a day or so, their mother leads them to the water in a little parade. She stays close to the ducklings and protects them until their flight feathers grow in. By the time the young ducks make their first long flight to their wintering grounds, they are completely on their own.
The parents and other adults lose their flight feathers as their breeding season ends. For a few weeks afterward they are unable to fly. At this time drakes usually grow a duller coat of feathers, which they keep for a few months before the more colorful feathers grow back in at breeding time. Ducks kept by people have lived 20 years, but the average life span in the wild is much shorter.
Ducks and people
Ducks have been domesticated—kept and bred by humans—for thousands of years. Many people value ducks for the meat, eggs, and down they provide. The down is used to make warm clothing and bedding.
The duck is a popular game animal. Largely because of hunting, the Labrador duck became extinct in the late 1800s, and other ducks are now rare. Governments in some countries now keep track of wild ducks and control hunting. People who want to hunt waterfowl in the United States are required to buy a special stamp. Some of the money the government gets from selling the stamp is used to maintain breeding habitats.
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