The Wolverine: a Stealthy, Enigmatic Beast

Wolverine (Gulo gulo) in snow, Montana, USA (Animal model)
Mike Hill / Getty Images

The wolverine is a stealthy, mysterious beast haunting the wildest corners of the continent, and just as interesting (if not more) than the Marvel comic book character named after it.

Ecology and Environment

The wolverine is one of the largest members of the mustelid family, which includes weasels, martens, badgers, mink, and otters. It can weigh over 50 lbs -- the only larger members of the family are the ​sea otter and the tropical giant otter.

All mustelids are carnivores, but perhaps more than others wolverines have included carrion as an important part of their diet. Especially in winter, they will feed on the carcasses of large mammals like moose or mountain goats. Their jaws are powerful enough to break large bones to access the rich marrow inside. Wolverines are also opportunistic hunters and they will kill a wide range of mammals, from small rodents to deer and caribou.

To acquire all the resources they need, wolverines have very large home ranges, in the order of hundreds of square kilometers. Because of that, they occur at a very low density and are rarely seen. The vast territories add to the difficulties encountered to conserve the species, as protected areas rarely cover the entire territory of one or two animals.

Where Are Wolverines Found?

The geographic range of wolverines is very wide, reaching across the boreal forest biome, and reaching into the tundra. In North America, they occupy much of western and northern Canada, at least the portions with lowest human densities. They have been documented in the northern portions of Ontario and Quebec, but are now extremely rare there. In the United States, wolverines are found in Alaska, Washington, Idaho, Montana, Wyoming, and Oregon. Recent sightings suggest some individuals occasionally moving south into California and Colorado.

Wolverines are not unique to North America -- they have a circumpolar distribution, which means they are found in northern regions around the globe. In Europe and Asia, they used to roam widely but centuries of persecution have pushed them to the more remote parts of Scandinavia and Russia, including Siberia. There are some isolated populations in the mountains of northeast China and in Mongolia.

Threats to Wolverines

There was a time when wolverines were hunted and trapped (Montana allowed wolverine trapping until just a few years ago), but the observed declines in populations have mostly been attributed to a loss of habitat. Road development, mining activity, oil and gas development, forestry operations, and recreational activities (like snowmobiling) has contributed significantly to habitat fragmentation and disturbance.

In parts of Norway, Sweden, and Finland wolverines frequently prey on livestock like sheep and domesticated reindeer. When pursuing these animals, the predators run a high risk of being killed, legally or not, in an effort by ranchers to control losses. Efforts to minimize predation conflicts have been deployed, including incentives for ranchers to return to the traditional approach of using large livestock guardian dogs.

With their broad feet, wolverines are adapted to moving efficiently on snow, allowing them to forage for food in the long northern winter nights and high up in the mountains. Climate change is reducing the depth of the snowpack, and shortening the amount of time snow lingers in the spring, negatively affecting wolverine habitat. Most troublesome is the decline in availability of den locations: females dig dens out of the snow to give birth to one to five kits, needing a stable snowpack at least 5 feet deep to provide a well-insulated home for the newborns.

The wolverine is not currently protected under the U.S. Endangered Species Act, but soon might be. Conservation groups have long pushed the federal government to protect the species, and they have come close in 2013 when a threatened status was granted, but then withdrawn a year later. In 2016 a federal judge ruled that the effects of climate change were not properly considered in the decision to withdraw protection. The U.S. Fish & Wildlife Service is slated to announce the outcome of a new review.