Wolverine is a powerful carnivore of the weasel family (Mustelidae). The wolverine (Gulo gulo) formerly inhabited an area ranging from Scandinavia and Germany to northeastern Siberia. In North America it was found throughout Alaska and Canada and as far south as central California, southern Colorado, Indiana, and Pennsylvania.
Having disappeared from much of its previous territory, in Europe the wolverine is presently found only in parts of Scandinavia and the northern part of the former Soviet Union. The species has almost entirely disappeared from eastern and south-central Canada. It belongs to the order Carnivora, class Mammalia.
The wolverine has a combined head-and-body length ranging from 26 to 41 inches (65 to 105 cm) and a tail that is 7 to 10 inches (17 to 26 cm) long. It weighs between 15 and 70½ pounds (7 to 32 kg).
The animal has a heavy build; an arched back; a bearlike head; massive limbs; large feet; long hair; relatively small, round ears; and a short, bushy tail. It is mostly blackish brown, with a yellowish brown strip from shoulder to rump on each side. The forehead is white, and the undersurface, face, and tail tip are black.
In North America the species is found mainly in the tundra areas and coniferous forests of Alaska and British Columbia. In parts of Canada that are above the 55th parallel, it lives in forests, mountains, and open plains. The wolverine constructs a bed of grass or leaves in a cave or rock crevice, in the burrow of another animal, or under fallen trees. Maternal dens in Finland are often dug into the snow.
Reproduction, Development, and Longevity
The wolverine's mating season lasts from late April to July. However, the implantation of the fertilized egg into the uterus is delayed until sometime between November and March, after which the gestation period continues usually for 30 to 40 days. There are normally two to four young with each litter. Newborns weigh between 3 and 31/2 ounces (90 to 100 grams).
Females give birth approximately every two years. The young are weaned after eight to ten weeks and leave their mother in autumn, attaining adult size by the end of their first year. Sexual maturity is reached at 2 to 3 years of age. One captive wolverine lived for 17 years and 4 months.
Behavior and Diet
The wolverine is primarily solitary, not associating with other members of its species except during mating season. Exhibiting considerable strength for a mammal of its size, it is an excellent climber and swimmer and is capable of traveling great distances without rest. Although G. gulo is mainly nocturnal, it is sometimes active during the day.
The species' diet includes large mammals, such as reindeer, roe deer, and wild sheep. These are obtained usually as carrion, but wolverines will hunt their own prey as well. In both cases G. gulo will cover the dead animal with earth or snow or wedge it in the fork of a tree. It also feeds on lemmings, berries, and the eggs of ground-nesting birds.
The wolverine is valued for its coat, which accumulates less frost than other types of fur. However, the species is apparently more often hunted because of fears that it will attack livestock or interfere with fur trappers who are seeking other types of animals. By the early 20th century wolverines were almost extinct in the contiguous United States. The population has since grown, however, and small numbers of G. gulo have subsequently been reported from northern California to western Montana.
The World Conservation Union has classified the wolverine populations of Canada, the United States, Estonia, Finland, Mongolia, Norway, Russia, and Sweden as vulnerable. This designation means that the species is not yet considered endangered but is at risk of falling into that category in the future.