Fact Sheet
Wolverine

Basic Facts About Wolverines

Called "skunk bear" by the Blackfeet Indians, the wolverine (Gulo gulo) is the largest terrestrial member of the weasel family and currently roams the rugged and beautiful Rocky Mountains and North Cascades in the western U.S.

A larger cousin to otters, weasels and mink, the wolverine has a broad head, small eyes and short rounded ears with dark brown fur, and often has a lighter-colored face mask and stripe running down both sides of its body. Typically weighing less than 35 pounds, the wolverine is powerfully built and has short legs with wide feet for traveling across the snow.

Did You Know?

Wolverines have unique coloration patterns on their face, neck, and chest that can allow researchers to identify individual animals based on photos showing the patterns.

These animals are a vital part of ecosystems in northern climes, and a great ambassador of the wild places they inhabit and the melting snow they require. Wolverines are also exceedingly rare, with scientists estimating that fewer than 300 wolverines may live in the lower 48 states, possibly fewer.

Diet

Wolverines are opportunistic feeders and eat a variety of foods depending on availability. In the winter they primarily scavenge dead animals, while in the summer their diet consists mainly of smaller mammals such as porcupines, hares, marmots and ground squirrels. They can also take down much larger animals, including caribou and moose, when circumstances such as deep snow are in their favor.

Did You Know?

It is easy to mistake other animals as a wolverine. Other species that may be commonly misidentified as wolverines include the American badgers, hoary marmots, small black bears or cubs, fishers, and dark colored red foxes.

Population

Based on current knowledge of wolverine habitat and wolverine densities in this habitat, scientists estimate that the wolverine population in the contiguous United States numbers approximately 250 to 300 individuals. Far fewer are successfully contributing to the gene pool in any given year.

Range & Habitat

Wolverines in the Lower 48 live in rugged, remote country, spending most of their time in high elevations near or above timberline. Further north in Alaska and Canada, wolverines occur within a wide variety of elevations in alpine, boreal and arctic habitats, including boreal forests, tundra and western mountains.  

Historically, wolverines once lived in the northern and southern Rocky Mountains, Sierra Nevada Mountains, and North Cascades Mountains, as well as in parts of the Midwest and the Northeast. Today, wolverines in the Lower 48 can be found in portions of the North Cascades Mountains in Washington and the northern Rocky Mountains in Montana, Idaho and Wyoming (this area also includes the Wallowa Range in Oregon). There have been lone individuals found in Michigan’s forests, the southern Rocky Mountains in Colorado, and the Sierra Nevada Mountains in California.

Did You Know?

While many carnivores eschew feeding on bones, wolverines have extremely strong teeth and jaws that can break and eat meat and the bones - fresh or frozen!

Behavior

Wolverines do not hibernate and are well-adapted for winter existence, with extremely dense fur, large snowshoe-like paws that allow them to stay on top of deep snow, and crampon-like claws that enable them to climb up and over steep cliffs and snow-covered peaks.

Wolverines are highly effective scavengers, with their keen sense of smell, strong teeth that crunch up bones, and their legendary ability to travel year-round through extreme alpine environments and over extraordinary distances. Wolverines have been documented traveling great distances, often going right over mountains instead of taking the easy way around. Individual wolverines may move more than 18 miles in one night. One male wolverine near Yellowstone traveled more than 500 miles in 42 days!

Wolverines are territorial animals and defend large, gender-exclusive territories. They naturally occur at low population densities. Yet, surprisingly, wolverines have a social side. Male and female territories overlap each other, and they have strong family bonds. A male wolverine will interact with his kits even after they have struck out on their own.

Reproduction

Female wolverines give birth in winter in dens that provide security and a buffer to cold winter temperatures. These dens are generally tunneled through snow and are associated with uprooted trees, avalanche debris, and boulders, often in remote alpine cirques at or above tree line. Young wolverines are called kits, and are born white as snow.

Mating Season: Late spring to late summer
Gestation: Egg implantation is delayed until the following winter or spring, followed by a 30 to 45-day gestation period.
Litter Size: 1 - 5 kits, with an average in North America of 1 - 2 kits

More on Wolverine: Threats to Wolverines »

You may also be interested in:

Hammerhead Shark, © Tui De Roy / Minden Pictures
In the Magazine
New Hope for Hammerheads; From Doves to Condors; Wolverine Woes
Polar bear, © Tom Schneider
Conservation Issue
Climate change is now one of the leading threats to wildlife. Find out what Defenders is doing to help animals around the country survive in a warming planet.
How You Can Help
Tell Secretary Jewell to stop ignoring threats to wolverines and give them full protection before it’s too late!