Wolverine

As opportunistic hunters, the wolverine diet ranges from small eggs to large ungulates (mammals with hooves) and can vary by season. Throughout the year, they feed on small and medium-sized animals like voles, squirrels, hares, and birds. In the winter, they generally rely on the remains of moose and caribou killed by other predators or animals that have died of natural causes. They can bring down prey that is five times larger than themselves, including reindeer and elk, when the animal is weakened or when the snow is deep enough to slow the prey down.

At the Zoo, the wolverines receive a prepared ground carnivore diet, fish, rats, bones, and other food-based enrichment.

In North America, wolverines are found in Alaska, northern Canada, and some of the northern states in the western U.S. Populations are also found in northern Europe and Eurasia, including Scandanavia and Russia.

Historically, the species was found in more southernly regions of Europe and United States. These populations were eliminated from these areas during the 19th century due to hunting and other human activities.

Found in alpine forests, tundra, and transition zone habitats at or above timberline. They prefer large, undisturbed areas with low human development. The species is found exclusively in areas with cold climates.

Wolverines have very few, if any, natural predators. They are impressively fierce and can defend themselves against animals several times their size. However, wolves, bears, mountain lions, and golden eagles can be threats to young or inexperienced wolverines.

Humans and human activity play the biggest threat to wolverines. Human encroachment, overhunting of both wolverines and their large prey, habitat fragmentation, and global warming all play a role in decreased wolverine populations.

Wolverine fur is usually darker brown with a yellowish stripe extending from the crown of the head, splitting over the shoulders and back end, then meeting back together at the tail. Their fur is long and dense for warmth in the cold environments they inhabit. They have stocky bodies with short, strong limbs. This keeps them low to the ground and they move in a loping gallop. The semi-retractable claws are long and curved, allowing them to climb and grip well. Large “snowshoe” feet enable them to walk on top of deep snow, rather than sinking.

Males and females come together briefly for mating, usually in the summer. Wolverines have delayed implantation, meaning the fertilized embryo is not implanted into the uterus to begin developing until early winter. This allows a female to become pregnant when food supplies are best and when she is in good physical condition. The abundance of resources determines whether a pregnancy will be maintained and the number of young that will be born -- females will often not produce young if food is scarce.

During the winter, females construct dens to store food and hide young. They will collect grasses and leaves to line nests in caves, rock crevices, burrows made by other animals, and hollows inside or under trees. They occasionally construct burrows under packed snow. Kits are born inside the den between January and April. The average litter size is 2 to 4 kits and they are born blind, weighing less than one pound, and with white fur. Kits are weaned at about 8 weeks and begin foraging on their own around 6 months, when they become independent.

Because of their scavenging lifestyle over very large ranges, wolverines have an excellent sense of smell. They generally communicate via scent glands and urine marking. They are rarely vocal, except for the occasional grunts and growls when irritated.

Wolverines are generally solitary and territorial. Their territories are vast: adult males can claim up to 240 square miles and females up to 100 square miles. Individuals will travel up to 25 miles in a day inside this territory in search of food. Wolverines tolerate snow well and do not hibernate or migrate to avoid cold weather conditions. The wolverine can be active at any time during the day or night, year-round. Although generally found on the ground, they can climb trees quickly and are excellent swimmers.