Dog Family

I

Introduction

Dog Family, group of 38 species of carnivorous (meat-eating) mammals that includes the wolf, coyote, jackal, fox, zorro, dingo, dhole, and domestic dog. Dogs, also called canids, have large canine teeth, long muzzles, and blunt, non-retractile 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 northern timber or grey 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 far out on ice floes and above timberlines. The rare bush dog inhabits savannahs of equatorial South America.

Canids show remarkable genetic plasticity—that is, strains or varieties of species rapidly adapt their size and build to different climates and physical conditions. 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 3,500 years ago.

II

General Behaviour

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 fox leaps into the air to locate its prey by sound and smell and then pounces on it. Canids are essentially carnivorous, but many species also eat fruit and other vegetable matter to tide them through periods when prey is scarce. They feed mainly on mice, voles, larger rodents, and especially rabbits, and also eat large insects and carrion. Large canids also prey on hoofed animals.

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 are made up 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 human beings.

Canids have territories, or home ranges, which they mark off by urine or scent posts. The range of the grey wolf varies from 18 to 13,000 sq km (7 to 5,000 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. Wolves will not tolerate coyotes in their territories, and some authorities believe that should grey wolves return to the forested areas of the eastern United States, they would drive out the coyotes.

Barks, growls, yelps, whimpers, and howls are associated with different modes of behaviour such as greeting, submission, play, or courtship. The raising or lowering of the ears or tail and the ruffling the neck hairs are also used as forms of communication—particularly submission or threat—among canids (seeAnimal Behaviour).

III

Reproduction

The gestation period of most canids ranges from 50 to 70 days and oestrus (heat) 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.

IV

Evolution

Members of the dog family, like other carnivores, evolved from a genet-like, tree-climbing carnivorous mammal of the Eocene epoch (56.5 million to 35.4 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, about 35.4 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 carnivores, and remained so right up to the Holocene epoch. The first wolves and foxes appeared at about the upper Pliocene (5.2 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.