Photo by Daniel J. Cox/NaturalExposures.com
At a Glance
The wolverine is known for its incredible strength and intelligence. The bear-like member of the weasel family is adapted for survival in harsh winter conditions and deep snow.
Range: Northern Rockies and Northern Cascades, Alaska and Canada
Habitat Type: High-elevation habitats at and around treeline
Primary Diet: Carrion, small animals and birds, berries and insects
Estimated Population(in contiguous US): Fewer than 500 in the northern Rockies; an unknown, small number in the Cascades. The “effective population” size – those that breed and contribute to the gene pool – is estimated to be fewer than 50.
States with Current Habitat
Wolverines in the lower 48 states are threatened by the low number of individuals contributing to their genetic diversity, as well as the low overall population number; relative isolation from populations in Canada; global warming (which reduces the snow pack wolverines rely on for den sites); winter recreation in denning areas; and trapping in Montana.
Why Protection is Needed
Low populations - The lower 48 population of wolverines is reduced to a perilously low number. Their breeding population is estimated at fewer than 50 individuals. Compounding the problem, wolverines in the western U.S. are segmented into subpopulations effectively separated by low valleys, altered land uses or other obstacles. This has resulted in decreased genetic exchange and decreased ability for self-sustaining populations or repopulation of areas that may be suitable for recovery, such as the Southern Rockies and Sierra Nevada.
Global warming - Wolverines rely on snow packs that last into late spring to successfully raise young kits. Global warming is resulting in a loss of springtime snow pack and this loss may accelerate. The result may be further isolation of different populations as the vital alpine habitat becomes restricted more and more to higher elevations.
Human disturbances and trapping - Resource extraction, roads, winter recreation (such as snowmobiling and helicopter skiing) and other disturbances near denning sites may negatively impact the ability of wolverines to reproduce. In addition, Montana continues to maintain an annual trapping season for wolverines, despite their low population number and the risk it poses to maintaining a self-sustaining population.
In March, 2008 the U.S. Fish and Wildlife Service (FWS) refused a petition to list wolverines in the contiguous 48 states as endangered, despite their own recognition that the wolverines in the Northern Rockies and Cascades are facing serious threats. FWS used a controversial interpretation of the Endangered Species Act to justify its decision, declaring the species safe due to larger populations in Canada and Alaska. If this interpretation had been used throughout the Act’s 35 years as law, species such as the Bald Eagle would likely never have recovered in the lower 48. In September 2008, a group of ten conservation organizations filed suit to challenge the FWS’ decision not to protect wolverines in the lower 48.