views updated




The domestic dog


Canines are species in the carnivore family, Canidae, including the wolves, coyote, foxes, dingo, jackals, and several species of wild dog. The family also includes the domestic dog, which is believed to have descended from the wolf. The Canidae includes 1014 genera with 3035 species, depending on the taxonomic treatment.

Canines originated in North America during the Eocene era (3854 million years ago); from there they spread throughout the world. The social behavior of canines varies from solitary habits to highly organized, cooperative packs. Canines range in size from the fennec fox, about 16.5 in (41 cm) long including the tail, and weighing about 2.23 lb (11.5 kg), to the gray or timber wolf, which is more than 6 ft (2 m) in length and weighs up to 175 lb (87.5 kg).

Canid skulls have a long muzzle, well-developed jaws, and a dental formula of 42 teeth. Most canines species live in packs, which offer several benefits including group defense of territory, communal care of the young, and the ability to catch large prey species.


Wolves are found in North America, Europe, and Asia. The gray wolf (Canis lupus ) is the largest member of the dog family, and is a widely distributed species. It lives in a variety of habitats, including forest, prairie, mountains, tundra, and desert. The red wolf (Canis rufus ) is found only in southeastern Texas and southern Louisiana. The red wolf is smaller than the gray wolf, and it may be a hybrid between the gray wolf and coyote (Canis latrans ).

The gray wolf lives in packs and is a territorial species. Territories are scent marked, and range from 50 to 5,000 sq mi (12812,800 sq km) in area. Pack size is usually about eight members, consisting of a mature male and female, their offspring, and close relatives. A system of dominance hierarchy is established within the pack. The dominant male leader of the pack is called the alpha male, and the dominant female is the alpha female. Hierarchy is acknowledged among pack members through submissive facial expressions and body postures.

Only the dominant male and female breed. Gestation is about two months and the average litter size is four to seven pups, which are born blind. The young are weaned within five weeks and reach physical maturity within the year, but do not become sexually mature until the end of their second year. The non-breeding members of a pack will help to protect and feed the young. The prey species of the wolf include deer, moose, elk, caribou, and beavers.

Besides scent marking, wolves communicate by howling. It is believed that howling lets dispersed pack members know each others position, and warns other packs off the territory. During the spring and summer, the wolf pack has a stationary phase and remains within its territory. It is during this period that the pups are raised. During the nomadic phase in autumn and winter, wolf packs travel widely, often following the migration of prey species.


There are 21 species of foxes in four genera. Foxes range in size from the 3 lb (1.5 kg) fennec fox (Vulpes zerda ) to the 20 lb (10 kg) red fox (Vulpes vulpes ). The gray fox (Urocyon cinereoargenteus ) and arctic fox (Alopex lagopus ) are highly valued for their pelts. Color phases of the arctic fox include the silver fox and blue fox. Species found in the United States are the kit fox (Vulpes macrotis ) and the swift fox (V. velox ), which live on the western plains. Other species of Central or South America include the crab-eating fox (Cerdocyon thous ), the sand fox (Vulpes rueppelli ), and the Corsac fox (Vulpes corsac ).

Foxes have a pointed muzzle, large ears, a slender skull, and a long bushy tail. They are territorial and scent-mark their territories. They use stealth and dash-and-grab hunting techniques to catch their prey. Foxes are generally solitary hunters and most species feed on rabbits, rodents, and birds, as well as beetles, grasshoppers, and earthworms. Foxes mate in winter, having a litter of one to six pups after a gestation period of 5060 days. Besides scent marking, foxes proclaim their territory by vocalizations such as yapping, howling, barking, whimpering, and screaming.

Foxes are heavily hunted for their pelts. They also may be killed to prevent the spread of the viral disease rabies. Some efforts at oral vaccination for rabies have been successful in Switzerland and Canada.

Coyotes, jackals, the dingo, and species of wild dog comprise the rest of the canine family. Coyotes are found from Alaska to Central America. Coyote populations have flourished as wolves have been eliminated. Coyotes have interbred with wolves and with domestic dogs. They prey on small animals, but will also feed on carrion, insects, and fruit. Coyotes reach maturity within a year and produce a litter of about six pups. While the basic social unit of coyotes is the breeding pair, some coyotes form packs similar to wolves and scent-mark territory. In the United States, coyotes have been responsible for considerable losses of sheep.

There are four species of jackals. In warmer parts of the world, jackals fill the same ecological niche as wolves and coyotes do in temperate and colder regions. Jackals are found throughout Africa, southeastern Europe, and southern Asia as far east as Myanmar. The four species are the golden jackal (Canis aureus ), the simien jackal (C. simensis ), the black-backed jackal (C. mesomelas ), and the side-striped jackal (C. adustus ). The golden jackal prefers arid grasslands, and is the most widely distributed of the four species. The black-backed jackal prefers brushy woodlands, the simien jackal the high mountains of Ethiopia, and the side-striped jackal moist woodland. Jackals have a varied diet of fruit, reptiles, birds, and small mammals.

Jackals are unusually stable in their breeding relationships, forming long-lasting partnerships. They also engage in cooperative hunting. Jackals are territorial and engage in scent marking, usually as a male and female pair that tends to remain monogamous. Jackals communicate by howling, barking, and yelping. In Ethiopia, the simien jackal is an endangered species primarily due to habitat loss.

Other wild canines include the Asiatic wild dog or dhole (Cuon alpinus ) of Southeast Asia and China, the maned wolf (Chrysocyon brachyurus ) of Central Asia, the bush dog (Speothos venaticus ) of Central America and northern South America, the dingo (Canis dingo ) of Australia, and the raccoon dog (Nyctereutes procyonoides ) of eastern Asia. In Africa, the African wild dog (Lycaon pictus ) hunts in packs which can overpower large mammal species.

The domestic dog

Kennel societies in the United States recognize 130 breeds of domestic dog, while those in Britain recognize 170 breeds, and the Federation Cynologique Internationale (representing 65 countries) recognizes 335 breeds. The size range of domestic dogs is from about 3 lb (2 kg) to 200 lb (100 kg). Some breeds, such as the dachshund, have short legs; while others, such as the greyhound, have long legs.

For dog owners, these animals can serve a number of different purposes. Pet dogs provide companionship and protection, while working dogs may herd sheep or cattle, or work as sled dogs. Police use dogs to sniff out illegal drugs and to help apprehend criminals. Dogs are also used for hunting and for racing. Guide dogs help blind people find their way around.

Female dogs may reproduce at an age of seven to 18 months. Gestation lasts about two months, and the size of a litter is from three to six puppies. Born unable to see, like other canines, domestic dog puppies develop all their senses by 21 days. Around the age of two months, puppies are less dependent on their mother and begin to relate more to other dogs and people. Typical vocalizations of domestic dogs include barking and yelping.

About 10, 000 years ago human civilization changed from a hunting and gathering society to a farming culture, and the domestication of the dog began. However, dogs probably also associated with humans before this time. It is believed that all breeds of domestic dogs, whether small or large, long-haired or short-haired, are descended from a wolf-like animal. Breeds of domestic dogs have been produced through selective breeding. One distinguishing feature between domestic dogs and wolves is the orbital angle of the skull. Dogs have a larger angle, which is measured from lines at the top of the skull and at the side of the skull at the eye socket.


Alpha male or female The dominant male or female in a pack of wolves.

Dominance hierarchy Rank-ordering among animals, with dominant and submissive ranks.

Opportunistic predator An animal that eats what is available, either killing its own prey, stealing food from other predators, or eating plant material, such as berries.

Stationary or nomadic phase Seasonal periods in which animals may remain within a specific area, usually during the breeding season, as compared to nomadic periods when the group moves extensively to follow prey.

The dog, sometimes known as mans best friend, is treasured by humans. Dog stories abound in childrens literature, from Lassie to Rin Tin Tin, and many politicians, including Presidents Franklin D. Roosevelt and Richard Nixon, used dogs to enhance their personal image.

Excessive hunting for their fur or as pests, often coupled with the destruction of habitat, have endangered some species of canines. Their reputation as predators has added to efforts to eradicate them from areas where livestock is raised or where they live close to human settlements. Some of the rare wild dogs, for instance the simien jackal of Ethiopia, are very few in number. The Asiatic wild dog has a population of fewer than 2, 500 mature individuals, and the African wild dog is found in similarly low numbers. A successful effort has been made to reintroduce the gray wolf into Yellowstone National Park in the United States, but this has been opposed by many local ranchers.



Alderton, David. Foxes, Wolves and Wild Dogs of the World. New York: Facts on File, 2004.

Carey, Alan. Twilight Hunters: Wolves, Coyotes, and Foxes. Flagstaff, Arizona: Northland Press, 1987.

Creel, Scott, and Nancy M. Creel. The African Wild Dog: Behavior, Ecology and Conservation. Princeton, NJ: Princeton University Press, 2002.

Nowak, Ronald M. Walkers Mammals of the World. 6th ed. Baltimore: The Johns Hopkins University Press, 1999.

Olsen, Stanley John. Origins of the Domestic Dog: The Fossil Record. Tucson, Arizona: University of Arizona Press, 1985.

Sheldon, Jennifer W. Wild Dogs: The Natural History of the Non-Domestic Canidae. San Diego: Academic Press, 1992.

Wolves. San Francisco: Sierra Club Books, 1990.

Vita Richman