U.S. Fish & Wildlife Service Wolverine Gulo Gulo luscus Roy Andersen ©

Wolverine Species Description The wolverine is the largest Deep, persistent, spring snow is suitable wolverine habitat in the terrestrial mustelid (a member of required for successful wolverine Great Lakes area (such as year- the weasel family). Adult males reproduction because female round cold and persistent spring typically weigh 26 to 40 pounds, wolverines dig elaborate dens in the snow), we have concluded that this while adult females average 17 to snow for their offspring. These den region, as well as areas further east, 26 pounds. The wolverine resembles structures are thought to protect likely did not support resident a small bear with a bushy tail, a wolverine kits from predators and wolverines in the past and does not broad head, small eyes, and short, the harsh conditions of alpine provide climatic conditions suitable rounded ears. Wolverines have winters. for wolverine occupancy and glossy, dark-brown fur, a light face reproduction today. mask, and stripes running down Range both sides of their bodies. They are Wolverines live in remote and powerfully-built animals, with short inhospitable places, at high legs and wide feet built for traveling elevations away from human across deep snow. Each foot has five populations. They naturally occur at toes with curved, semi-retractile low densities, and are rarely claws used for digging and climbing. encountered where they do occur. In the contiguous United Habitat States, wolverines currently occur The North American wolverine in the North Cascades Range in

inhabits arctic, boreal, (northern, Washington and the Northern Roy Andersen sub-arctic forest) and alpine Rocky Mountains of Montana, © habitats in Alaska, western Canada, Idaho, and Wyoming. Wolverines and the western contiguous United once existed in the Sierra Nevada Diet States. South of the Canadian Mountains of California and the Wolverines, while primarily border, wolverines are restricted to Southern Rocky Mountains in carnivorous scavengers, are high mountain environments near Colorado. However, at least one opportunistic feeders that consume the treeline, where conditions are individual wolverine is currently a variety of foods, depending on cold year-round and snow cover known to inhabit each of these availability. They are known for persists well into the month of May. areas, and these animals are scavenging the carrion of large thought to be recent migrants. animals like elk, deer, and moose, but they are also capable of killing A small number of historical records small mammals and birds. confirm that wolverines once Wolverines prey upon pikas, occurred in the Great Lakes region marmots, ground squirrels, of the United States and Canada. porcupines, and snowshoe hares. However, based on the low number Occasionally, wolverines also

Steve Kroschel of records and the current lack of consume insects, eggs, berries, and © roots. Wolverine in snow

Region 6 Mountain Prairie Region Reproduction Wolverines breed from late spring increasing rates of loss of genetic the scientific information currently to early fall. Females give birth diversity and making the retention available, the U.S. Fish and Wildlife between February and April to of small populations more difficult. Service has determined that litters containing one to five young, Other threats have the potential to protection for the contiguous with an average of between 1 and 2 act in concert with climate change United States distinct population kits. to exacerbate impacts on segment of the North American wolverines. Recreation, especially wolverine is warranted under the Wolverine reproduction is food- during the denning season, is one Endangered Species Act (ESA). limited, meaning that females often such threat, as mother wolverines However, we have determined that are not able to bear and raise young tend to move their kits to alternate proposing the species for protection to adulthood due to lack of denning areas once humans have is precluded at this time by the need nutritional resources. Female been detected nearby. Recreational to take action on other species wolverines only reproduce every activities such as snowmobiling and facing more immediate and severe other year on average, enabling backcountry skiing have the extinction threats. As a result, the them to conserve energy and potential to affect wolverines. wolverine has been placed on the improve the odds of success in However, further research is list of species that are candidates for breeding years. This erratic needed to confirm whether these ESA Protection. We will review the reproduction pattern, combined activities have measurable impacts status of the species annually, as we with small litter sizes, makes the on the species. do for all candidate species, and will reproductive rate for wolverines propose the species for protection one of the lowest known for when funding and workload mammals. priorities for other listing actions allow. Population Scientists estimate that 250 to 300 More Information wolverines inhabit the contiguous To learn more about the North United States, while 15,000 to American wolverine, please visit 20,000 animals are thought to live in the following site: Canada. http://www.fws.gov/mountain- prairie/species/mammals/wolverine/ Threats Climate change is the threat with the greatest potential to impact the North American wolverine. A U.S. Fish and Wildlife Service warming climate will likely result in Region 6, NWRS Roy Andersen

a loss of suitable habitat due to © increased summer temperatures Wolverine profile U.S. Fish and Wildlife Service and a reduced incidence of PO Box 25486 persistent spring snowpack. Denver Federal Center While recreation has the potential Denver, Colorado 80225 According to analyses completed by to affect the wolverine, it does not 308 / 382 6468 the University of Washington’s currently seem to be suppressing Climate Impacts Group and the populations. Similarly, the primary For State relay service USDA Forest Service’s Rocky threat of climate change has not so TTY / Voice: 711 Mountain Research Station, far resulted in any detectable wolverine habitat in the contiguous U.S. Fish & Wildlife Service population-level effects to the http://www.fws.gov United States is likely to decrease species. Therefore, we have in aerial extent by 23% by 2045 and concluded that these threats are not December 2010 63% by 2099. With lower elevation imminent to wolverines at this time. habits becoming unsuitable, remaining wolverine habitat is Legal Status under the Endangered likely to become more fragmented. Species Act Connectivity between remaining After thoroughly evaluating all of wolverine habitats will be reduced,

Region 6 Mountain Prairie Region