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.
