dog, carnivorous, domesticated wolf wolf, carnivorous mammal of the genus Canis in the dog family. Once distributed over most of the Northern Hemisphere, wild wolves are now confined to the wilder parts of a reduced range.
..... Click the link for more information. (Canis lupus familiaris) of the family Canidae, to which the jackal jackal, name for several Old World carnivorous mammals of the genus Canis, which also includes the dog and the wolf . Jackals are found in Africa and S Asia, where they inhabit deserts, grasslands, and brush country.
..... Click the link for more information. and fox fox, carnivorous mammal of the dog family, found throughout most of the Northern Hemisphere. It has a pointed face, short legs, long, thick fur, and a tail about one half to two thirds as long as the head and body, depending on the species.
..... Click the link for more information. also belong. The family Canidae is sometimes referred to as the dog family, and its characteristics, e.g., long muzzle, large canine teeth, and long tail, as canine traits. However, the unmodified term dog usually refers only to the domestic subspecies Canis lupus familiaris.

Two characteristics distinguish the dog from other canids and, indeed, from all other animal species. The first is its worldwide distribution in close association with humans, encompassing both hemispheres from the tropics to the Arctic. The second is the enormous amount of variability found within the subspecies. For example, the Irish wolfhound may stand as high as 39 in. (99.1 cm) at the shoulder, while the Chihuahua's shoulder is usually no more than 6 in. (15.2 cm) from the ground; the silky coat of the Yorkshire terrier may be 2 ft (61 cm) long, while a few breeds of dog (such as the Mexican hairless) are entirely without hair. The evolution of such widely differing breeds has been heavily influenced by conscious human selection, in addition to natural evolution.

Dogs have been selectively bred through the centuries for special purposes, notably to pursue and retrieve game, as draft animals, as guides (e.g., for the blind), and as companions. Although dogs possess hearing abilities far superior to humans', their acute sense of smell is probably the sense most utilized. In addition to traditional hunting and tracking, the dog's sense of smell has been put to such diverse uses as the location of exotic foods and the detection of drugs and explosives, e.g., in luggage and packages.

Dogs can be protected against serious diseases for which vaccines are available; these include distemper distemper, in veterinary medicine, highly contagious, catarrhal, often fatal disease of dogs. It also affects wolves, foxes, mink, raccoons, and ferrets. Distemper is caused by a filtrable virus that is airborne; it is also spread by infected utensils, brushes, and
..... Click the link for more information. , canine hepatitis, leptospirosis leptospirosis (lĕp'təspīrō`sĭs), febrile disease caused by bacteria of the genus Leptospirae.
..... Click the link for more information. , and rabies rabies (rā`bēz, ră`–) or hydrophobia
..... Click the link for more information. .

Early Dogs

The dog is descended from the wolf. True wolves appeared in Europe about one million years ago and in the Americas some 700,000 years later. Dog remains estimated to be about 14,000 years old have been found in Germany, and younger remains have been found in Israel (about 13,500 years old) and Idaho (about 10,500 years old). It is probable that the dog was the first animal to be domesticated, most likely around 15,000 years ago. Domestication may have occurred independently in a number of different areas of the world, but genetic tests show that all dogs are descended from an Eurasian stock, even the now extinct pre-Columbian dogs of the Americas.

It is thought that the earliest domesticated dogs resembled the present-day dingo dingo (dĭng`gō), wild dog (Canis lupus dingo
..... Click the link for more information. , the wild dog of Australia. The dingo is believed to have come to Australia as a domestic dog with the aborigines from Southeast Asia. Although more historical information exists on the forerunners of European dogs (such as the British hounds, terriers, and shepherd dogs) than on those of other areas, there is evidence that dogs have existed in most areas of the world throughout the period of recorded history. One of the oldest known breeds is the basenji basenji (bəsĕn`jē)
..... Click the link for more information. , which originated in central Africa and is still used as a hunter by certain tribes in that region. Several distinct breeds were known in ancient Egypt and a mastifflike breed (resembling the Kurdish dog in present-day Iraq) is found in Babylonian illustrations of c.2200 B.C.

Dog Breeds

The Purebred Dog

A breed of dog is produced by selecting and mating dogs with certain desired characteristics. The offspring of such matings are then inbred, i.e., mated with litter mates or close relatives. After about eight generations, the line usually breeds true, i.e., most offspring resemble each other. Then standard traits can be established for the new breed. A purebred dog is one that conforms to the standards of a certain breed and whose lineage, or pedigree, has been recorded for a certain period of time.

One of the principal functions of a kennel club is to maintain the records of lineage of individual purebred dogs in order to preserve breed standards. The stud books of the AKC contain entries for all purebred dogs whose owners have elected to register their dog's pedigree. Other stud books, such as those of the United Kennel Club, often record dogs of breeds not recognized by the AKC but which have a considerable following in the United States. Dogs of mixed origin or whose parentage is unknown are called mongrels.

Classification of Breeds

Attempts to classify dogs probably date from the time when humans discovered that certain canine traits were more useful than others. The earliest known system of classification, that of the Romans, included categories for house dogs, shepherd dogs, sporting dogs, war dogs, dogs that ran by scent, and dogs that ran by sight. Today there are systems of classification and breeding in most countries of Western Europe and in North America, many using a variation of the standard British system.

In the United States, the classification system most frequently encountered is that employed by the American Kennel Club (AKC), which recognizes more than 150 of the more than 200 known breeds. The breeds are grouped into six classes. In the sporting dog sporting dog, classification used by breeders and kennel clubs to designate dogs bred for pointing, flushing, and retrieving game. These dogs hunt by air scent—as opposed to most hounds, which are ground scenters—and their quarry is primarily game birds.
..... Click the link for more information. group are pointers pointer, breed of large sporting dog developed in England more than 300 years ago. It stands between 23 and 26 in. (58.4–66.4 cm) high at the shoulder and weighs between 50 and 60 lb (22.7–27.2 kg).
..... Click the link for more information. , retrievers, setters, and spaniels. These dogs hunt by air scent as opposed to those of the hound hound, classification used by breeders and kennel clubs to designate dogs bred to hunt animals. Most of the dogs in this group hunt by scent, their quarry ranging from such large game as bear or elk to small game and vermin; ground scenters trail slowly with the head
..... Click the link for more information. group, e.g., beagles beagle, breed of small, compact hound developed over centuries in England and introduced into the United States in the 1870s. It stands between 10 and 15 in. (25.4–38.1 cm) high at the shoulder and weighs between 20 and 40 lb (9.1–18.1 kg).
..... Click the link for more information. , foxhounds, and bloodhounds bloodhound, breed of large hound whose ancestors were known in the Mediterranean region before the Christian era. It stands about 25 in. (63.5 cm) high at the shoulder and weighs between 80 and 110 lb (36.3–49.9 kg).
..... Click the link for more information. , which track their prey by ground scent. Also classified as hounds are those dogs of the greyhound greyhound, breed of tall, swift, sight hound developed nearly 5,000 years ago in Egypt. It stands about 26 in. (66 cm) high at the shoulder and weighs about 65 lb (29.5 kg).
..... Click the link for more information. type, e.g., whippets whippet, breed of small, slender hound developed in England in the mid-18th cent. It stands between 18 and 22 in. (45.7–55.8 cm) high at the shoulder and weighs about 20 lb (9 kg). Its close-lying, smooth coat may be any color but is usually white, tan, or gray.
..... Click the link for more information. , borzois borzoi (bôr`zoi), breed of tall, swift hound developed in Russia in the early 17th cent., also called Russian wolfhound.
..... Click the link for more information. , and Salukis Saluki (səl
..... Click the link for more information. , which hunt mainly by sight. The many breeds of terrier terrier, classification used by breeders and kennel clubs to designate dogs originally bred to start small game and vermin from their burrows or, in the case of several breeds in this group, to go to earth and kill their prey.
..... Click the link for more information. go to earth after their burrowing prey. Among the working dog working dog, classification used by breeders and kennel clubs to designate dogs raised by humans to herd cattle and sheep, as draft animals, as message dispatchers in wartime, in police and rescue work, as guardians of persons and property, or as guides (see guide
..... Click the link for more information. group, used as guards, guides, and herders, are the collie collie, breed of large, agile working dog developed in Scotland during the 17th and 18th cent. It stands from 22 to 26 in. (55.9–66 cm) high at the shoulder and weighs from 50 to 75 lb (22.7–34 kg).
..... Click the link for more information. , the German shepherd German shepherd, breed of large, muscular working dog perfected in Germany at the turn of the 20th cent. It stands about 25 in. (64 cm) high at the shoulder and weighs from 60 to 85 lb (27.2–38.5 kg).
..... Click the link for more information. , and the St. Bernard Saint Bernard, breed of massive working dog developed in Switzerland in the 18th cent. and perfected by British breeders during the 19th cent. It stands from 25 to 29 in. (64–74 cm) high at the shoulder and weighs from 140 to 170 lb (64–77 kg).
..... Click the link for more information. . Such diminutive pet dogs as the Pekingese Pekingese (pē'kĭnēz`), breed of small toy dog developed over many centuries in China. It stands from 6 to 9 in. (15.3–22.
..... Click the link for more information. , the Pomeranian Pomeranian (pŏm'ərā`nēən), breed of small, sturdy toy dog descended from the sledge dogs of Iceland and Lapland.
..... Click the link for more information. , and the pug pug, breed of sturdy, compact toy dog that became popular in England during the 19th cent. It stands about 11 in. (27.9 cm) high at the shoulder and weighs from 14 to 18 lb (6.4–8.2 kg).
..... Click the link for more information. belong to the toy dog toy dog, classification used by breeders and kennel clubs to designate very small breeds of dogs kept as pets. Some are selectively bred diminutive forms of larger breeds and others are naturally small.
..... Click the link for more information. class. The nonsporting dog nonsporting dog, classification used by breeders and kennel clubs to designate dogs that may formerly have been bred to hunt or work but that are now raised chiefly as house pets and companions.
..... Click the link for more information. group is a class of dogs bred principally as pets and companions and includes the Boston terrier Boston terrier, breed of small, lively nonsporting dog developed in the United States in the second half of the 19th cent. It stands between 14 and 17 in. (35.6–43.2 cm) high at the shoulder and weighs from 13 to 25 lb (5.9–11.3 kg).
..... Click the link for more information. , the bulldog bulldog, breed of thick-set nonsporting dog developed in the British Isles many centuries ago. It stands from 13 to 15 in. (33–38.1 cm) high at the shoulder and weighs from 40 to 50 lb (18.1–22.7 kg).
..... Click the link for more information. , the chow chow chow chow, breed of powerful nonsporting dog whose origins are obscure but whose development was accomplished many centuries ago in China. It stands from 18 to 20 in. (45.7–50.8 cm) high at the shoulder and weighs from 50 to 60 lb (22.7–27.2 kg).
..... Click the link for more information. , the Dalmatian Dalmatian (dălmā`shən)
..... Click the link for more information. , and the poodle poodle, popular breed of dog probably originating in Germany but generally associated with France, where it has been raised for centuries. There are three varieties, differing in size only.
..... Click the link for more information. . In addition to the breeds in the above classes, the AKC currently places additional breeds in a miscellaneous group; breeds recently recognized by the club are placed in this class until they become established. Included are the Akita Akita (äkē`tə), breed of large dog developed in Japan from ancient ancestry and used originally as a hunter of such game as
..... Click the link for more information. of Japan, the Australian cattle dog Australian cattle dog, breed of medium-sized herding dog developed in Australia. It stands from 18 to 20 in. (45.7–50.8 cm) high at the shoulder and weighs about 33 lb (15 kg).
..... Click the link for more information. , the Australian kelpie Australian kelpie, breed of medium-sized sheepherding dog originating in Australia c.1870. It stands from 17 to 20 in. (43.2–50.8 cm) high at the shoulder and weighs from 25 to 30 lb (11.3–13.6 kg).
..... Click the link for more information. , the Bichon Frise Bichon Frise (bēshôN` frēs), breed of small dog developed in France after World War I. It stands from 8 to 12 in.
..... Click the link for more information. (a French descendant of the water spaniel), the border collie border collie, breed of medium-sized, sheepherding dog developed in the British Isles. It stands about 18 in. (45.7 cm) high at the shoulder and weighs from 30 to 45 lb (13.6–20.4 kg).
..... Click the link for more information. (an English shepherd dog), the cavalier King Charles spaniel cavalier King Charles spaniel, breed of small dog developed in the early 20th cent. from the English toy spaniel. It stands about 12 in. (30 cm) high at the shoulder and weighs from 13 to 18 lb (6–8 kg).
..... Click the link for more information. , the Ibizan hound Ibizan hound (ēbē`zŏn, ĭb`ə–)
..... Click the link for more information. (of Spanish origin), the miniature bull terrier miniature bull terrier, breed of small, muscular dog developed in England in the early 19th cent. It stands up to 14 in. (35.6 cm) high at the shoulder and weighs about 17 lb (7.7 kg). Its short, flat, harsh coat is glossy white or white with brindle patches.
..... Click the link for more information. , the soft-coated wheaten terrier soft-coated wheaten terrier, breed of medium-sized dog developed and perfected in Ireland. It stands from 17 to 19 in. (43.1–48.3 cm) high at the shoulder and weighs from 30 to 45 lb (13.6–20.4 kg).
..... Click the link for more information. (from Ireland), the Spinone Italiano Spinone Italiano (spĭnō`nē ĭtălēä`nō, Ital.
..... Click the link for more information. , and the Tibetan terrier Tibetan terrier, breed of medium-sized dog originating in Tibet probably several thousand years ago. It stands from 14 to 16 in. (35.6–40.6 cm) high at the shoulder and weighs from 15 to 30 lb (6.8–13.6 kg).
..... Click the link for more information. .

Dogs registered by the AKC and other registry associations compete regularly in dog shows and field trials. In dog shows, the various breeds are judged solely on appearance, while in field trials they are rated according to their hunting skills.

See articles on individual dog breeds.

Reproduction

Female dogs, or bitches, will mate only when in heat, or estrus, which occurs about every six months and lasts from 18 to 22 days. Whelping (giving birth) occurs after a gestation period of about nine weeks. The size of the litter varies to some extent with the size of the dog: toy dogs rarely bear more than 2 puppies, while the largest breeds average closer to 10.

Bibliography

See E. Schneider-Leyer, Dogs of the World (1960); American Kennel Club, The Complete Dog Book (1968); E. H. Hart, Encyclopedia of Dog Breeds (1968); H. P. Davis, ed., The New Dog Encyclopedia (rev. ed. 1973).

dog

Any member of the canine genus Canis, particularly the domestic species, Canis familiaris. Domestic dogs seem to have decended from the wolf or a wolflike ancestor. Dogs were apparently the first animals to be domesticated, and domestication seems to have begun in various parts of the world at roughly the same time. Selective breeding by humans has resulted in myriad domestic breeds that vary widely in size (from the tiny Chihuahua to the huge mastiff), physical form (e.g., the short-legged dachshund and the flat-faced bulldog), coat texture and length (e.g., the sleek Doberman pinscher and the long-haired Afghan hound), and behavioral patterns (e.g., sporting dogs, toy dogs, and working dogs). The American Kennel Club now recognizes almost 150 breeds; other clubs, such as the United Kennel Club, recognize many more.

dog

a. a domesticated canine mammal, Canis familiaris, occurring in many breeds that show a great variety in size and form

b. (as modifier): dog biscuit

a. any other carnivore of the family Canidae, such as the dingo and coyote

b. (as modifier): the dog family

a. the male of animals of the dog family

b. (as modifier): a dog fox

4. a mechanical device for gripping or holding, esp one of the axial slots by which gear wheels or shafts are engaged to transmit torque

5. any of various atmospheric phenomena

dog

ever pictured at feet of saints; “man’s best friend.” [Medieval Art: Brewer Dictionary, 332; Western Folklore: Misc.]

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