Wolverine (Gulo gulo luscus)

Wolverine walking across snow
Photo by Steve Kroschel - U.S. Fish and Wildlife Service publication

Wolverine walking across snow.

Category: Mammals
State status: Candidate
Federal ESA status: Threatened
Vulnerability to climate change (More details)

High

If you see this species, please share your observation using the WDFW wildlife reporting form. Providing detailed information such as a photo and exact coordinates will improve the confidence and value of this observation to WDFW species conservation and management.

Washington's wolverine population occurs throughout the Cascade Mountain Range and appears to be connected to the population in southern British Columbia. The loss and fragmentation of habitat due to climate change is considered the greatest threat to wolverines in Washington. Vehicle collision (at least 3 documented carcass removals of wolverine on Washington roads between 2018-2022) and predation may also be important sources of mortality.

Description and Range

Physical description

The wolverine is the largest terrestrial member of the weasel family, with females weighing 18 to 27 pounds and males weighing 26 to 44 pounds. Wolverines are stocky with short, rounded ears, small eyes, a bushy tail, and large feet that are useful for travelling through snow. Their fur is dark brown, but has tawny colored bands that run down both sides of its body to its tail.

Ecology and life history

Wolverines commonly occur in boreal forest, taiga, and tundra ecosystems. In Washington, they occupy alpine and subalpine forest habitats. 

A wolverine in the wild looking straight ahead
Photo by Roy Anderson - U.S. Fish and Wildlife Service publication
A wolverine climbing over rocky terrain.

For an animal of their size, wolverines use extraordinarily large activity areas (from 40 to greater than 770 square miles).

Denning sites are commonly located in north and northeastern facing cirque habitats, where snow commonly persists through the spring and into the summer months.  Dens are typically associated with a passage through deep snow to a space within talus or under a fallen tree or other large woody debris.

Wolverines are prey generalists, and commonly feed on small and mid-sized mammals and ungulate carrion. They may opportunistically kill adult ungulates.

Predators include gray wolves, cougars, and other wolverines.

Geographic range

Wolverines occur in the remote mountainous areas of the Cascades and in northeastern Washington.  In the Cascade Range, wolverines occupy high-elevation landscapes from North Cascades National Park and Okanogan-Wenatchee National Forest south to Mount Adams on the Gifford Pinchot National Forest.  A population of 13 wolverines was studied in the North Cascades from 2005 to 2013  Wolverines were extirpated from Washington in the mid-1900s as a result of predator control and persecution, however they became reestablished in the North Cascades beginning in the 1990s and in the South Cascades (i.e., south of Interstate 90) by 2008. 

Reproduction has been documented in Northern Cascades since 2005, and litters of wolverine kits were photographed in the vicinity of Mount Rainier National Park in 2018 and 2020. The population in the Cascades is probably less than 25 individuals, however this population appears to be relatively stable.

For maps of range-wide distribution and conservation status of this species check out NatureServe Explorer and the International Union for Conservation of Nature Redlist. 

Climate vulnerability

Sensitivity to climate change

High

Wolverines exhibit sensitivity to temperature and declines in snowpack. The species is obligatorily associated with persistent spring snow cover, which provides critical thermal advantages such as predator refugia for denning females and young, preventing competition with other scavengers, and important prey caching/refrigeration areas. Temperature appears to play a role in fine-scale habitat selection and may affect prey caching success. Warming temperatures and declines in snowpack could lead to decreased habitat patch size, quality, and connectivity; reduced success of caching/refrigeration of carrion prey with subsequent impacts on survivorship and recruitment; limited den sites and/or loss of thermal refugia important for juvenile survival; and reduced dispersal abilities. Because wolverines are adapted to cooler temperatures, animals in the southern portions of the species’ geographic range (e.g., Washington) may experience greater physiological stress as summer temperatures increase in the coming decades.

Confidence: High

Exposure to climate change

High

  • Reduced snowpack
  • Increased temperatures
Confidence: Moderate

Conservation
This species is identified as a Species of Greatest Conservation Need (SGCN) under the State Wildlife Action Plan (SWAP). SGCN-classified species include both those with and without legal protection status under the Federal or State Endangered Species programs, as well as game species with low populations. The WDFW SWAP is part of a nationwide effort by all 50 states and five U.S. territories to develop conservation action plans for fish, wildlife and their natural habitats—identifying opportunities for species' recovery before they are imperiled and more limited.
This species is identified as a Priority Species under WDFW's Priority Habitat and Species Program. Priority species require protective measures for their survival due to their population status, sensitivity to habitat alteration, and/or recreational, commercial, or tribal importance. The PHS program is the agency's main means of sharing fish and wildlife information with local governments, landowners, and others who use it to protect priority habitats for land use planning.
Two WDFW biologists examine a wolverine for a winter project in Okanogan County
Photo by WDFW
WDFW biologists examine "Rocky" the wolverine for a winter project in Okanogan County.

Conservation Threats and Actions Needed 

  • Resource information collection needs
    • Threat: Information on abundance, movements, the effects of climate change on habitat quantity and configuration is lacking for the Cascade Mountain Range.
    • Action Needed: Continue monitoring activities throughout suitable habitat in the Cascade Mountain Range to reassess occupancy, changes in distribution, and possible responses to habitat loss and fragmentation.  
  • Habitat loss or fragmentation
    • Threat:  Barriers or impediments to movement across Interstate 90 in the central Washington Cascades may impede demographic support between the North and South Cascades.  Large highways are also a threat to wolverines that can be killed when trying to cross.
    • Action Needed: Continue surveys specifically to detect wolverine passage and continue development of passage structures and habitat corridors to facilitate successful crossings.
  • Climate change and severe weather
    • Threat: Loss of denning habitat and foraging habitat due to climate change.
    • Action Needed: Improve or maintain access to unoccupied denning and foraging habitat throughout the Cascade Mountain Range (as identified in “Habitat loss or fragmentation” above). See the Climate vulnerability section for more information about threats posed by climate change to this species.

 

Resources

References

Aubry, K. B., J. Rohrer, C. M. Raley, and S. H. Fitkin. 2013. Wolverine distribution and ecology in the North Cascades Ecosystem, 2013 annual report. Pacific Northwest Research Station, U.S. Forest Service, Olympia, Washington.

Copeland, J. P., and J. S.Whitman. 2003. Wolverine (Gulo gulo). Pages 672-682 in G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors. Wild mammals of North America: biology, management and conservation, 2nd edition. Johns Hopkins University Press, Baltimore, Maryland.

WDFW publications

Other resources