Wolverine Facts and Video - Defenders of Wildlife

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Called "skunk bear" by the Blackfeet Indians, the wolverine is the largest terrestrial member of the weasel family. It has a broad head, small eyes and short rounded ears. The wolverines have glossy dark brown fur, a light face mask and a stripe running down both sides of its body. It is powerfully built and has short legs with wide feet for traveling across the snow.

Fast Facts

Male wolverines are typically 30-40% larger than females.
Height: 16 inches (.41m) (males); 14 inches (.36m) at shoulders (females)
Length: 31-44 inches (.8 - 1.1m) (including its bushy tail)
Weight: 25-55 lbs (11-18 kg) (males), 15-30 lbs (7-14 kg) (females). Exceptionally large males can weigh over 70 lbs (31 kg)
Lifespan: 10-12 years.

Diet

Wolverines are known for scavenging dead animals like caribou or moose but are also very capable of killing their own meal, including ground squirrels and snowshoe hares.

Population

Fewer than 500 wolverines remain in the lower 48 states, according to the latest estimate by the U.S. Fish and Wildlife Service, possibly far fewer. Only 32 wolverines in the U.S. appear to be successfully breeding and getting their genes into the gene pool according to analyses by the U.S. Forest Service.

Range

Did You Know?

Wolverine fur is thick, oily, and hydrophobic, which means it's resistant to frost, water and snow.

To blend in with their snowy environment, wolverine kits (young) are white when they are born.

Wolverines prefer scattered trees at high elevations. Historically they occurred from Maine to Washington down to the Rocky Mountains and Sierra/Cascade Mountains. In the lower 48 states, wolverines now occur only in Wyoming, Idaho, Montana, Washington and may still occur in the Great Lakes region. Wolverines were believed to be extirpated from California, but a remote camera caught one on film in February 2008! See a wolverine range map >>

Behavior

Wolverines have been documented traveling great distances, often going right over mountains instead of taking the easy way around. One male wolverine near Yellowstone traveled more than 500 miles in 42 days.

Watch a Wolverine at Play

Reproduction
Mating Season May through August
Gestation Egg implantation is delayed, following which is a 30-40-day gestation period
Litter Size 2-3 kits
The females dig dens eight feet or deeper into the snow in the middle of winter, often in remote alpine cirques at or above treeline.

Climate Change and Other Threats

Wolverine habitat is being threatened by climate change. As temperatures rise, more of the wolverine’s snowy mountainous habitat is being lost. This will shrink their range to higher elevations and more northerly latitudes. The impacts of climate change are also seen in the female wolverine’s denning. Wolverines need areas that maintain deep snow from February to early May for their dens so they can provide protection for their kits. With less snow and smaller areas of cool, mountainous habitat, food and denning areas are decreasing.

Defenders at Work

Wolverines still survive in the western U.S. but are at risk due to low breeding numbers. They face threats from habitat loss and habitat fragmentation and more and more areas of wolverine denning habitat are disturbed by snowmobiles and helicopter skiing. Further, Montana and Alaska still allow wolverines to be trapped.

Reducing or reversing the effects of global climate change is one of the most important things that can be done to maintain wolverines and their snowy habitats. Equally important now, we can reduce other stressors on wolverines. Noisy and polluting snowmobiles are now powerful enough to access the previously pristine mountain snowfields where mother wolverines birth and raise their kits from February through May. Defenders is working with wolverine biologists and the U.S. Forest Service to ensure sufficient wolverine denning habitat is protected from harmful disturbance by motorized recreation. Defenders also works to reduce and eventually end trapping of wolverines in Montana.

Learn more >>

Reasons For Hope

Wolverines all but disappeared in the lower 48 states by the early 1900s due to poisoning and trapping targeted at wolves, coyotes and other predators, to the point that the wolverine’s known range was reduced to Glacier National Park in northwestern Montana. Since that time they have expanded their range to include much of western Montana, northwestern Wyoming, north-central Idaho and north-central Washington. During the past few years, dispersing wolverines have been documented in Oregon, California and Colorado, giving hope that they may be able to recolonize much of their former range in the American West.

Defenders challenged the March 2008 decision by the Fish and Wildlife Service to not protect wolverines under the Endangered Species Act (ESA). In a settlement agreement filed with the court in June 2009, the Fish and Wildlife Service agreed to reconsider whether to add the wolverine population in the lower-48 states to the list of species protected by the ESA. The new listing determination is due by December 2010, and will follow an updated status review of the wolverine. Learn more >>

Legal Status/Protection

On the International Union for the Conservation of Nature Red List, the wolverine is currently listed as a species of least concern.
In March 2008, the Fish and Wildlife Service decided not to protect wolverines under the Endangered Species Act. FWS said that the United States does not need to protect wolverines in the lower-48 states, because wolverines are not endangered in Canada. Defenders of Wildlife is now challenging this decision, because we believe that America should protect its own wildlife, not rely on other countries to save them. We are optimistic that we will succeed, and soon gain wolverines the protections they need and deserve.
The wolverine is legally trapped in Montana and Alaska.
Learn more about legal status and protection for wolverines >>

How You Can Help

Help wolverines and other wildlife by adopting an animal at our Wildlife Adoption Center.
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