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Dog Family, group of at least 36 species of
carnivorous mammals that includes the wolf,
coyote, jackal, fox, common zorro, dingo, dhole (red
dog), and domestic dog.
Dogs, also called canids, have large canine teeth, long muzzles, and blunt, nonretractable claws; all but the African hunting dog have five toes on the forefeet and four toes on the hind feet. They vary in size from the tiny desert-dwelling fennec, which weighs 1.5 kg (3.2 lb), to the gray or timber wolf, which weighs 20 to 80 kg (44 to 175 lb). Canids are found throughout all the continents except Antarctica and in nearly every climatic zone; the arctic fox lives on ice floes and above timberlines, while the rare bush dog inhabits savannas of equatorial South America.
Canids show remarkable genetic plasticity; that is, strains or varieties of species rapidly adapt their size and other physical characteristics to different climates and habitats. The Australian dingo has probably adapted twice, first to become domesticated in prehistoric Asia and then to become a wild species in Australia when it was introduced there about 10,000 years ago.
Canids have highly developed senses of smell and hearing, enabling them to hunt by night as well as in the daytime. They work territories, usually at a tireless trot or canter, breaking into a gallop to pursue prey. The long red fox leaps into the air to spot mice, then pounces on them. Canids are essentially carnivorous, but many species will also eat fruit and other vegetable matter to tide them through prey-scarce periods. They feed mainly on mice, voles, and larger rodents, especially rabbits, and will also eat large insects and carrion. Large canids also prey on hoofed animals, such as antelope, caribou, and deer.
Some species of canids work primarily in relays or packs. Relay hunters, such as the African hunting dog, take turns running down hoofed animals. Wolves and Indian dholes hunt in packs. Dhole packs, which consist of several families and number up to 30 members, have been known to take on tigers and Himalayan bears. Few if any reports exist of unprovoked wolf or dhole attacks on humans.
Canids have territories, or home ranges, which they mark off by urine or scent posts. The range of the gray wolf varies from 18 to 13,000 sq km (7 to 5000 sq mi), whereas that of a fox may be only 5 to 50 sq km (2 to 20 sq mi). In more solitary canids such as foxes, the range may depend on gender, age, and food availability.
Barks, growls, yelps, whimpers, and howls are associated with different behaviors such as greeting, submission, play, or courtship. The raising or lowering of the ears or tail and the ruffling the neck hairs are also forms of communication among canids.
The gestation period of most canids ranges from 50 to 70 days and occurs once a year. Canids produce from 2 to 13 offspring, which usually are reared in a burrow. The pups are born blind, and those of some foxes are suckled for as long as ten weeks. Canids become sexually mature in one or two years.
Members of the dog family, like other carnivores, evolved from a genet-like, tree-climbing carnivorous mammal of the Eocene Epoch (55 million to 38 million years ago). Although dogs were once grouped with carnivores such as the bears and raccoons, they are now considered to be more closely linked in their evolution with cats. During the early Oligocene Epoch (34 million to 24 million years ago), as many as 50 dog-like animals appeared, with good running legs and well-developed, blunt-clawed toes. They were probably the most successful line of the carnivores, and remained so until about 1.6 million years ago. The first wolves and foxes appeared at about the upper Pliocene Epoch (5 million to 1.6 million years ago). The African hunting dog, the dhole, and the South American bush dog probably developed along separate lines that branched off from the Eocene Epoch dog at about the same time as hyenas.
Until recent decades, most wild canids were hunted for bounties and considered scourges to livestock and other wildlife. The elimination of coyotes and foxes from some areas, however, has resulted in huge increases in rodent populations that eat vegetation intended for desirable livestock and wildlife. Because wolves, coyotes, and foxes usually eliminate the weaker, less adaptable members of rodent and ungulate (hoofed-mammal) species, some wildlife biologists consider these predators necessary to maintain the genetic strength of such prey species.
Dogs and Wolves
The eight species of dogs and wolves include the well-known gray wolf. This animal, which formerly ranged throughout Europe, Asia, and North America, has been driven in reduced numbers to wilderness areas of these continents. The red wolf, once found from Pennsylvania to Texas and Florida, is now an endangered species. The coyote, on the other hand, has expanded its population into the eastern United States and is now found in every state except Hawaii. Three species of jackal, also a true canid, primarily inhabit Africa. Until recently the jackal was thought to be an ancestor of the domestic dog, but because the jackal is less social than the domestic dog, has a narrower, fox-like head, and howls unlike any domestic dog, this possibility is now doubted. The gray wolf appears to be the only ancestor of the modern domestic dog.
The red fox is the best known of the 21 fox species. Red foxes can live in close proximity to humans, and their wariness and keen senses of sight, smell, and hearing have earned them the reputation of cleverness. They have good endurance and run gracefully, reaching a speed of 48 km/h (30 mph). Foxes emit a strong "foxy" odor from the caudal glands near the tail. When seen in strong light, the pupils of their eyes are elliptical, or oval shaped; those of wolves are round.
The raccoon dog, named for its masked facial markings, lives in eastern Siberia, Japan, and parts of China. A long-haired, bushy-tailed animal, it is one of the least dog-like canids. In northern climates it hibernates through much of the winter.
The maned wolf of Brazil and northern Argentina looks like a stilt-legged red fox with an erect mane on the back of the neck and top of the shoulders. Although it is close to the height of the gray wolf, it has a much slighter build and is not a true wolf. Maned wolves are nocturnal and usually solitary; they are not swift-running, and stalk then pounce on prey.
By contrast the South American bush dog is a stocky, short-legged, short-eared, and short-tailed canid that lives in forests and savannas. Bush dogs hunt by night in packs of ten or less and have been observed pursuing pacas (large South American rodents) into water. One bush dog in captivity acted much like a domestic dog except that it could dive and even swim under water.
The Falkland Island dog, now extinct, was reportedly an unwary and curious animal, which followed early explorers through these islands off the southern coast of Argentina. When the islands were settled, the dogs were killed for fur or to protect sheep herds, and by 1876 they had been exterminated.
Scientific classification: Canids make up the family Canidae, of the order Carnivora. The African hunting dog is classified as Lycaon pictus, the fennec fox as Fennecus zerda, the gray wolf as Canis lupis, and the arctic fox as Alopex lagopus. The bush dog is classified as Speothos venaticus, the dhole as Cuon alpinus, the red wolf as Canis rufus, and the coyote as Canis latrans. Jackals belong to the genus Canis. The domestic dog is classified as Canis familiaris, and the red fox as Vulpes vulpes. The raccoon dog is classified as Nyctereutes procyonoides, the maned wolf as Chrysocyon brachyurus, and the Falkland Island dog as Dusicyon australis.
Dog, Domestic, carnivorous mammal, 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.
Recognizing Established Breeds
Standards of desired sizes, colors, and conformation for each breed are drawn up by committees elected by members of the various kennel clubs specializing in each breed. In the U.S. these standards are then approved by the AKC. The standards, issued since 1929, represent an ideal dog and are used as guides for breeders and dog-show judges in evaluating the degree of quality of each dog. Standards may differ from country to countrynot all dogs are developed to serve the same purposes or are judged according to the same rules.
Care and Training of Family Pets
Proper food, a dry bed, sufficient exercise, and affectionate care are necessary to keep a dog a happy, healthy member of the family. To make certain it will please everyone and fit into the familys life-style, a dog should be selected only after a family conference has determined the desired size and possible function of the dog, and whether it is to be long-haired or short-haired, male or female, mixed breed or purebred.
The New Puppy
Reputable kennels will inform prospective buyers if a puppy is healthy and has had its preliminary shots, and will also guarantee pedigree. In general, puppies should be acquired at the age of between six and eight weeksafter they have been weaned and have attained full psychological developmentso that a bond with human beings can effectively be made.
Food, dishes, toys, a collar and leash, and a bed should be purchased before the arrival of a new puppy. Owners should learn how to pick up a dog correctly: one hand under the front legs and the other supporting the hindquarters. Puppies require daily supplementary feedings up to the age of about 4 months. (Dogs reach full maturity at about 2 years of age and generally live to be 12 or 13 years old.)
All members of the family should share equally in feeding, walking, and playing with the new dog so that it will not become too attached to any one member of the household. All states require that dogs wear licenses; the fee required is minimal. A license attests that a dog has had rabies and distemper shots and states when they were administered, and it ensures identification if a dog is lost.
Role of the Veterinarian
A veterinary checkup within two or three days of purchase is necessary to confirm a dogs health and to set up a schedule for vaccinations against the devastating viral diseases most common to canines: canine distemper and rabies, which affect the nervous system; infectious canine hepatitis, which attacks the liver; and the highly contagious intestinal disease caused by the parvo virus, first detected in the United States in 1978. Inoculations against leptospirosis, a bacterial infection, are also essential. At the initial visit the veterinarian will also check the dog for any anatomical defects that might interfere with proper development, usefulness, or future breeding and for internal and external parasites (worms, fleas, ticks, or lice). Annual checkups are as essential for dogs as they are for humans.
Veterinarians recommend that owners decide before their dogs reach sexual maturity (within the first year) whether pets are to be bred. If dogs are not to be bred, females should be spayed (surgical removal of the ovaries) and males should be neutered (surgical removal of the testes).
Training Your Dog
There are few things a dog would rather do than please its owner. Obedience training ensures good manners, and when correctly taughtusing the reward system and never punishmentdogs enjoy working on the obedience exercises. Many books and manuals describe proper basic training with step-by-step instructions. Dog-training classes, sponsored by local kennel clubs and various community organizations, are also available. The ideal source of instruction and information concerning all phases of responsible dog ownership is a kennel club, where members share their interest in and knowledge of dogs.
Showing and Judging Dogs
Purebred dogs are eligible for competition at dog shows, which rate appearance, and field trials, which test hunting skills. In the U.S. the AKC records pedigrees and litter registrations on each of the recognized breeds and records points earned toward championship titles based on wins in the conformation classes at dog shows throughout the country. Although quarantine laws prevent dogs from other parts of the world from competing in Great Britain, dogs may attain international and world championships elsewhere under the rules and regulations of the Fédération Cynologique Internationale, the ruling body for dogs and dog shows in many countries. See Dog Shows and Trials.
The Relationship Between Human Beings and Dogs
The first dogs that joined forces with the cave dwellers were used for their keen hunting instincts and abilities, as a means of procuring food and skins for clothing, and for protection against predators. Civilizations that subsequently developed in both the eastern and western hemispheres depended on dogs and their cunning in the struggle for survival. Asians, Egyptians, Assyrians, Greeks, and Romans used dogs as guards, companions, and hunters and in times of war. Archaeological discoveriescave drawings and wall paintings, ancient artifacts and written recordsverify the role of dogs in early cultures in all parts of the world. Native Americans, both in North and South America, had several distinct dog breeds of their own before the first Europeans arrived.
Dogs in Art and Literature
Many great painters and sculptors managed to capture and reproduce the beauty and spirit of dogs in their masterpieces. The English artists Thomas Gainsborough, William Hogarth, and Sir Edwin Landseer, perhaps the greatest of all animal painters, are notable among the masters who routinely included pets in their family portraits and working dogs in their outdoor hunting or pastoral scenes.
Legends and myths based on the versatility and heroism of dogs abound; the subject of dogs is one of the most popular in world literature from the classics to modern comic strips.