Endangered Species
Mountain-Prairie Region


Wolverine in snow

Photo Credit: Steve Kroschel

The wolverine is the largest terrestrial member of the family Mustelidae.  Adult males weigh 12 to 18 kilograms (26 to 40 pounds) and adult females weigh 8 to 12 kilograms (17 to 26 pounds).  The wolverine resembles a small bear with a bushy tail.  It has a broad, rounded head; short, rounded ears; and small eyes.  Each foot has five toes with curved, semi-retractile claws used for digging and climbing.

In North America, wolverines occur within a wide variety of habitats, primarily boreal forests, tundra, and western mountains throughout Alaska and Canada; however, the southern portion of the range extends into the contiguous United States.

Currently, wolverines are found in the North Cascades in Washington and the Northern Rocky Mountains in Idaho, Montana, Oregon (Wallowa Range), and Wyoming.  Individual wolverines have also moved into historic range in the Sierra Nevada Mountains of California and the Southern Rocky Mountains of Colorado, but have not established breeding populations in these areas. 

Research indicates that wolverines either did not exist as established populations or were extirpated prior to settlement and to the compilation of historical records in the Great Lakes region, possibly due to climate changes that occurred through the 1800s and 1900s.  The widely scattered records from this region are consistent with dispersing individuals from a Canadian population that receded north early in the 1800s.  The possibility that wolverines existed as established populations prior to the onset of trapping in this area cannot be ruled out, but we have no evidence that they did.  No evidence in the historical records suggests that wolverines were ever present as established populations in the Great Plains, Midwest, or Northeast.

The delineation of wolverine historical and present distribution is inherently difficult for several reasons.  Wolverines tend to live in remote and inhospitable places away from human populations.  Wolverines naturally occur at low densities and are rarely and unpredictably encountered where they do occur.  Wolverines often move long distances in short periods of time when dispersing from natal ranges, making it difficult or impossible to distinguish with confidence between occurrence records that represent established populations and those that represent short-term occupancy without the potential for establishment of home ranges and reproduction.  These natural attributes of wolverines make it difficult to determine their present range, or trends in range expansion or contraction that may have occurred in the past. 

Breeding generally occurs from late spring to early fall.  Females undergo delayed implantation until the following winter to spring, when active gestation lasts from 30 to 40 days.  Litters are born between February and April, containing one to five kits, with an average in North America of between 1 and 2 kits.

Female wolverines use natal (birthing) dens that are excavated in snow. Persistent, stable snow greater than 1.5 meters (5 feet) deep appears to be a requirement for natal denning, because it provides security for offspring and buffers cold winter temperatures.

Wolverines are opportunistic feeders and consume a variety of foods depending on availability.  They primarily scavenge carrion, but also prey on small animals and birds, and eat fruits, berries, and insects.  Wolverines have an excellent sense of smell that enables them to find food beneath deep snow.

Wolverines require a lot of space; the availability and distribution of food is likely the primary factor in determining wolverine movements and home range size.  Wolverines travel long distances over rough terrain and deep snow, and adult males generally cover greater distances than females.  Home ranges of wolverines are very large, but vary greatly depending on availability of food, gender, age, and differences in habitat.  These home range sizes are large for mammals of the size of wolverines and may indicate that wolverines occupy a relatively unproductive niche.

Recent Actions : On August 13, 2014, the U.S. Fish and Wildlife Service withdrew a proposal to list the North American wolverine in the contiguous United States as a threatened species under the Endangered Species Act (ESA). The wolverine, a large but elusive member of the weasel family found in the Mountain West, has made a steady recovery in the past half century after hunting, trapping and poisoning nearly extirpated the species from the lower 48 states in the early 1900s.

While it is clear that the climate is warming, after carefully considering the best available science, the Service has determined that the effects of climate change are not likely to place the wolverine in danger of extinction now or in the foreseeable future. As a result, the wolverine does not meet the statutory definition of either a “threatened species” or an “endangered species” and does not warrant protection under the ESA.

August 13, 2014 Federal Register Notice

On April 2nd and 3rd of 2014, the Service convened a panel of scientific experts to provide input on the potential effects of future climate changes on wolverines and their habitat. The panel was organized in response to peer review and state comments we received after publication of the proposed rule to list wolverines. We are posting the results here so that people may provide comments to us about these results prior to the end the of the comment period which closes on May 6th, 2014. Please go to regulations.gov and search for "wolverine" to send us your comments.

Wolverine Science Panel Workshop Report 4/2014

February 4, 2014 - The U.S. Fish and Wildlife Service published a Federal Register notice that will extend the deadline for our final decision on whether to list the wolverine under the Endangered Species Act. The Act allows for such an extension when there is substantial scientific disagreement regarding the sufficiency or accuracy of the available data relevant to the decision at issue. During the peer review process on our proposed rule to list the wolverine as threatened, we received a variety of opinions from the scientific community concerning the information we used to develop the proposed rules. In response, we will be extending the deadline for the final listing decision by 6 months to further evaluate areas of scientific disagreement and uncertainty as they relate to the wolverine listing decision.

The new deadline for a final rule or withdrawal of the proposal will be August 4, 2014. With the Federal Register notice announcing the 6-month extension we are also reopening the comment period for the wolverine listing until May 6, 2014, details on the kinds of information the Service is seeking is available in the 6-month extension notice.

February 4, 2013: Wolverines were nearly extirpated from the contiguous United States in the early 20th century due to broad-scale predator trapping and poisoning programs.  Since that time they have made a remarkable recovery. Unfortunately, climate warming over the next century is likely to significantly reduce wolverine habitat, to the point where persistence of wolverines in the contiguous United States, without intervention, is in doubt.  Endangered Species Act (ESA) protection and actions by Federal and State agencies in partnership with private landowners and nongovernmental organizations can help protect the wolverine from extinction by increasing its ability to persist in the face of climate change. 

We are, therefore, proposing to protect the North American wolverine as a threatened species under the ESA. 

We are also proposing a special rule that would limit protections of the ESA only to those necessary to address the threats to the species. In the case of the wolverine, human activities in wolverine habitat such as snowmobiling, backcountry skiing, and land management activities like timber harvest and infrastructure development, which do not constitute threats to the species, would not be prohibited or regulated.  However, intentional killing of wolverines would be prohibited.   We are seeking input on whether or not it is appropriate to prohibit incidental take of wolverine in the course of legal trapping activities directed at other species, if states have programs in place to minimize the chances of this occurring.

A 90-day comment period, beginning February 4, 2013, is being provided to allow the public and stakeholders an opportunity to comment on these proposals.  During that time, we will also seek peer review from qualified members of the scientific community to ensure that our final decision is based on solid science.

The Service will make a final determination a year from now on whether to add the wolverine to the Federal List of Endangered and Threatened Wildlife based on the best available science. The Service will also decide whether or not it is prudent to designate critical habitat for the wolverine, and whether such a designation would be beneficial to this species given the threat to its habitat is climate change.

Information on how to submit public comments, including information on the public meetings and hearings that we will hold on the proposed rulemakings is provided below.

Scientific information regarding these proposals will be accepted until May 6, 2013 and can be submitted electronically via the Federal eRulemaking Portal at http://www.regulations.gov. Follow the instructions for submitting comments; or mailed or hand delivered to: Public Comments Processing, Attn: FWS-R6-ES-2012-0107; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, Suite 222; Arlington, VA 22203.

Public Hearings: Three informational sessions and public hearing will be held on this proposed rule.

  • Boise, Idaho:  March 13, 2013 at the Boise Centre on the Grove, 850 West Front Street, Boise, ID 83702.
  • Lakewood, Colorado: March 19, 2013 at the Hampton Inn, 137 Union Boulevard, Lakewood, CO 80228.  
  • Helena, Montana: March 27, 2013 at the Red Lion Colonial Inn, 2301 Colonial Drive, Helena, MT 59601.  

At all three locations the public informational session will run from 2:00 PM to 5:00 PM, followed by public speaker registration at 6:00 PM, and then the public hearing for oral testimony from 7:00 PM to 9:00 PM. 

Photos on Flickr


More information can be found at the Environmental Conservation Online System and the Information, Planning and Conservation System

Last updated: August 25, 2014