Dog Information

Dogs are carnivorous mammals, generally considered the first domesticated animal. The domesticated dog (Canis familiaris) has coexisted with human beings as a working partner and household pet in all eras and cultures since the days of the cave dwellers. It is generally believed that the direct ancestor of the domestic dog is the wolf, originally found throughout Europe, Asia, and North America. Remains of a dog, estimated to be 10,500 years old, have been found in Idaho.

Like other members of the dog family, C. familiaris exhibits great genetic variability; selective breeding by humans and the process of natural evolution have resulted in the development of hundreds of breeds found throughout the world today.

The breeds differ sharply in appearance, function, and size. Weights vary from that of the smallest companion dogs (680 g/1.5 lb) to that of the huge working breeds (90 kg/200 lb); heights, usually measured from the shoulder, range from 20 cm (8 in) to 94 cm (37 in). Litter sizes vary correspondingly. Gestation time in all breeds is nine weeks; although toy dogs produce no more than two puppies, the larger breeds may have litters of more than ten.

The breeds can be conveniently classified in groups; such classifications, and the breeds recognized within them, vary slightly from country to country. In the U.S., the American Kennel Club, or AKC, officially recognizes 138 breeds classified in 7 groups, as shown in the accompanying table; from time to time, as certain unofficially recognized breeds become established, they are promoted from a miscellaneous class to official status.