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.
October 31, 2013: The Service announced that we are reopening the comment period on the proposal to protect the North American wolverine as a threatened species under the ESA and the proposed special rule. The reopened comment period will last until December 2, 2013.
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.
- Federal Register Notice: February 4, 2013 Threatened Status for the Distinct Population Segment of the North American Wolverine Occurring in the Contiguous United States
- Federal Register Notice: February 4, 2013 Establishment of a Nonessential Experimental Population of the North American Wolverine in Colorado, Wyoming, and New Mexico
- Press Release: February 1, 2013 U.S. Fish and Wildlife Service Proposes to List Wolverines as Threatened under the Endangered Species Act
- Draft Recovery Outline
- Wolverine Proposed 10(j) Rule Literature Cited
- Wolverine Proposed Listing and 4(d) Literature Cited
- Modeled Wolverine Habitat Map
- Peer Review Plan
- Fact Sheet
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.
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