Gulo Facts

For anyone who comes here looking for basic information about wolverine life history and ecology, I encourage you to visit The Wolverine Foundation, where you will find the best in-depth information about current research, as well as succinct summaries about the species’ habits and conservation needs.

You might also take a look at The Northern Rockies Conservation Cooperative’s Wolverine Ecology page – NRCC coordinated field operations for the Absaroka-Beartooth Wolverine Project for five years, and is currently facilitating cooperative research and monitoring of wolverines in Wyoming.

Here are brief discussions of questions that seem to commonly lead people to this blog:

Where do wolverines live? Visit The Wolverine Foundation’s page on distribution – there are two maps that show worldwide and North American distribution. Wolverines live in places with tundra habitat, and, since they are dependent on persistent spring snowpack to den, they cannot establish breeding populations unless there is deep snow through late April or mid-May. They are also generally found only where the maximum temperature in August is 70° F. Today, wolverines are found in Scandinavia, Mongolia, parts of northern China, Siberia, Canada and the U.S. The southernmost distribution of wolverines in the U.S is Wyoming (where there is a confirmed breeding population), though individual males have reached Colorado and California. Michigan is probably not home to a breeding population of wolverines.

Tell me about wolverine reproduction and baby wolverines: Wolverines mate in the summer, but hold the fertilized eggs in suspension until winter, in a process known as delayed implantation. If resources are too scant for a female to successfully raise kits, the fetuses break down without implanting. If resources are adequate, the fetuses implant and the babies, called kits, are born in February. They are born pure white and totally helpless, and remain dependent on their mother until mid-May. Most of the time, wolverines have two kits at a time. Usually, even with a lot of food available, female wolverines give birth only once every two years, and only after they are three or four years old. This means that wolverines have a very slow rate of reproduction. In a study in Glacier National Park, the mortality rate of studied animals was nearly 50%, which means that the average female wolverine produces only one surviving kit every two years. So a female wolverine, even if she lives for ten years, has low reproductive potential.

Do wolverines have social lives? Wolverines have a reputation for being solitary and hostile, but research by Jeff Copeland and other wolverine biologists suggests that these animals may have a stronger sense of sociability and kinship than we thought, albeit perhaps mediated by scarce resources scattered over huge territories. Wolverines are territorial towards unrelated wolverines of the same sex – so a female won’t tolerate an unrelated female in her territory, and the same with two males – but male territories and female territories overlap, and male and female wolverines will travel together even outside the breeding season. Father wolverines visit the dens of their kits, and juvenile wolverines may remain in their parents’ territory for up to two years, sometimes traveling with their mother, sometimes with their father, and sometimes alone. A male wolverine will kill unrelated kits; if a resident male dies or is killed, a new male may come into the territory and put the kits at risk. Ensuring a stable population could therefore be important to kit survival and long-term population health.

What does a wolverine den look like? Wolverines den in the snow, which helps keep kits insulated and also protects them from predators. Wolverine dens are located in areas with deep snow through spring, and in places where there is a substructure of talus or downfall which forms natural caves under the snow. A wolverine den would be relatively inconspicuous – just a hole in the snow – but should have multiple sets of tracks leading to and from it. After a few weeks, a mother wolverine moves her kits from the natal den, where they were born, to a series of maternal dens. She may do this because the dens become unhealthy, with too many parasites. If you think you have found a wolverine den, please let us know; this could be important to researchers. Leave a comment here or contact The Northern Rockies Conservation Cooperative.

What effects do wolverines have on the environment? Wolverines are primarily scavengers, although they are capable of killing reindeer and other ungulates, especially if the ungulates are weak. Wolverines are unlikely to have a strong effect on prey species numbers. Nor do they have a strong effect on vegetation or the abiotic environment. They have been known to cause trouble for humans by breaking into cabins, raiding traplines, and preying on small domestic livestock (reindeer in Scandinavia, reportedly sheep and goats in Mongolia) but generally they are self-sufficient and don’t cause large-scale conflicts.

Are wolves or bears having a negative effect on wolverines? Probably not. A wolverine in Glacier was killed by a black bear at a carcass site, but wolverines are generally capable of holding their own and are also probably pretty good at knowing when to beat a retreat. In the US Rockies, wolves and wolverines don’t overlap much, since wolverines tend to live at such high altitudes, but where they do, wolves are likely to provide a net benefit to wolverines by leaving ungulate carcasses on the landscape. Wolverines seem highly adapted to obtain nutrition from the most unyielding scraps of bone and skin, so even a carcass that had been picked clean by a wolf pack would offer something to wolverines.

What are the threats to wolverines? North of the 54th parallel, wolverines are widespread and the population appears robust. As suitable habitat becomes more isolated further to the south, wolverines face greater challenges. If you think of mountain ranges as islands of wolverine habitat surrounded by an ocean of lower-altitude, unsuitable habitat, you begin to understand why maintaining connectivity and genetic diversity might become more difficult. It takes a lot of energy to travel 500 miles on foot through sagebrush desert from Wyoming to Colorado, as M56 did in 2009, in order to find a suitable territory in the nearest mountains. Along the way, a dispersing wolverine faces risks in the form of highways, and perhaps housing developments, traps set for other animals, or even someone mistaking it for a coyote and shooting it. Since each individual is so important to the population, the success or failure of a juvenile in reaching suitable habitat might have long-term effects.

Since wolverines are snow dependent in order to den, they are also facing the prospect of diminished habitat due to climate change, which would make the distances that a dispersing wolverine would have to travel even longer, while also limiting the amount of territory available to denning females.

Some people think that logging might threaten habitat, and others are concerned about winter recreation. There is no scientific evidence for the logging and recreation claims, but a research project in Idaho is currently trying to asses the risk of den disturbance from snowmobilers and backcountry skiers.

Montana is the only state in the Lower 48 that permits wolverine trapping. They have reduced their quota over the past three years, so that they now issue only 5 permits statewide, with a female subquota for each region (meaning that if a female is trapped in a region, the season automatically ends even if the quota hasn’t been filled.) The effects of trapping on the population have not been thoroughly quantified, but trapping is a concrete source of mortality which reduces the stability of the population. As mentioned above, this could have effects on kit mortality if males are removed from the population, and certainly on reproduction if an adult female is removed.

Animosity towards wolves has increased in the past few months in western states, and there is some evidence that anti-wolf groups have started leaving poisoned bait lying around in hopes of killing wolves. This stupid and irresponsible ploy has already resulted in death and illness for people’s pet dogs. Poisoned bait would also be tempting for a wolverine; in fact, the demise of the wolverine in its historic range in the Rockies was probably tied to wolf poisoning programs in the early 20th century.

What’s the status of wolverine conservation? In the US, environmental groups have petitioned for listing the wolverine under the Endangered Species Act three times, and in each case they were found not warranted for listing. In December of 2010, the wolverine was deemed “warranted but precluded,” meaning that the US Fish and Wildlife Service determined that wolverines in the Lower 48 do face substantial threats (primarily from climate change), but the government currently lacks the funding to implement a recovery plan. A group of environmental groups sued the USFWS to hasten decisions on species on the warranted-but-precluded list, some of which had been awaiting a status determination for more than 20 years. As a result of this lawsuit, a decision on wolverine status is anticipated by 2013.

Listing under the ESA is not a conservation solution, so much as a recognition of the need for further action. Because wolverines are dependent on snow, global warming constitutes a potential threat that will be hard to deal with under the current mandate of the ESA. Similarly, we know so little about wolverines that it will be difficult to determine what conservation or management strategies would best protect the species. If the wolverine is listed, it’s a step that acknowledges that threats exist, but the conservation community needs to be prepared to back and fund more research to address pressing questions about management strategies. Since wolverines in the Rockies exist as part of a wide-ranging, interconnected meta-population, conservation strategies will have to be both local and regional at the same time. Wolverine conservation will, of necessity, be ecosystem-level conservation.

How can I help the wolverine? Great question! First, you should learn more – an informed, scientifically literate constituency is important for any species, so indulge your interest, and then share it with others. A great introduction to wolverine biology and research is Doug Chadwick’s The Wolverine Way, about the research project in Glacier National Park. A PBS Nature documentary, Wolverine: Chasing the Phantom aired in 2010 and is a fun introduction too. And the Wolverine Foundation has the best collection of online material on wolverines.

Second, if you live in the Rockies, become a citizen scientist – if you see a wolverine, wolverine tracks, or other sign, report it by leaving a comment here or contacting NRCC, the Wolverine Foundation, or your state wildlife agency. NRCC and several other conservation groups have citizen science projects to help document wolverines; for an ID card that will tell you how to document and report a sighting so that it is considered verified, download an ID card from NRCC’s website.

Third, contribute directly to wolverine research by donating to NRCC’s project. Specify ‘wolverine’ in your comments. Wolverine research is logistically challenging and therefore expensive, but it is essential if we are going to understand how to conserve the species. When you become a part of this effort, you directly contribute to our work with F3, M57, and the other wolverines that you read about on this blog. If you can’t afford to contribute, encourage decision-makers to support wolverine conservation with research money.

Fourth, think about the wolverine and its ecosystem when you make your own day-to-day decisions. I’m not a fan of the apocalyptic panic-button variety of environmental narrative, but climate change is real, and it’s a real threat. So get creative and get active in the way you live your life – walk, run, or bike instead of driving; think about what you eat and what you wear and how those things have an effect on ecosystems and climate; vote the environment so that we have a system that recognizes and respects the intrinsic right of all creatures to exist, and of all humans to live in a healthy world; and – politely, with humor and creativity – encourage friends and family to make similar choices. In this sense, you are part of the wolverine’s ecosystem even if you live in a flat, hot place – say, Florida – and you can be directly beneficial to the conservation and protection of an amazing and inspiring animal.

How do I protect myself from vicious wolverines?  Wolverines are not a threat to humans unless rabid, or unless, hypothetically, a person is extremely weak and incapable of moving. There has never been a documented instance of a wolverine attacking a human. Wolverines sometimes do come towards people in the wilderness; they are curious and, according to some reports, their eyes are weak, so they may want a closer look. It’s best to be wary in these situations, but don’t assume that the wolverine is chasing or attacking you.

Wolverines can be a threat to pets. If there’s a wolverine in your neighborhood, keep your pets inside, especially between dusk and dawn. If you’re out with a dog in the wilderness, keep your dog close. If you happen to have a domestic reindeer, don’t let it wander around unattended; wolverines appear to find domestic reindeer quite tasty. Never back a wolverine into a corner; like any threatened animal, they will defend themselves, and they are probably more capable than most of doing damage.

If you have any other questions about wolverines, please ask.