Showing posts with label Wolverine. Show all posts
Showing posts with label Wolverine. Show all posts

08 February 2013

Friday Field Notes: All Eyes on the Wolverine

When it comes to wolverines in the news, the media is usually referring to a certain university in Michigan, not the aggressive, thirty-pound weasel that roams the high mountain ranges of the western United States. But following last week's announcement by the U.S. Fish & Wildlife Service that the large mustelids were being considered for "Threatened" status under the Endangered Species Act, even prominent news outlets like the New York Times and the Huffington Post couldn't keep their eyes off Gulo gulo.

The wolverine's scientific name, Gulo, comes from the Latin word for "glutton." However, despite the animal's ability to take prey of considerably larger body sizes than its own, the characterization of the wolverine as a glutton may actually be the result of a false etymology. Indeed, some researchers believe that the Swedish word used to describe wolverines (which in English translates to "mountain cat") is very similar to the German word vielfrass, which means "devours much"--and the rest is history. The common name "wolverine" is derived from the German word wolvering, which loosely translates to "little wolf" or "wolf-like."

They might look cute, but I've heard they have a bit of a temper.
A more appropriate name for the wolverine would be "little bear." In the rare event that people actually do see a wolverine in the wild (usually from some distance away), they often mistake them at first for bear cubs. It's hard to blame them: wolverines can be over three feet long and weigh upwards of 70 pounds! At nearly twice the size of their cousin the fisher (Martes pennanti), it becomes obvious that wolverines are not your ordinary weasel. When it comes to meal time, wolverines are actually more like bears than weasels. While prey often consists of small mammals such as shrews, voles, and rabbits, wolverines have been known to take animals as large as white-tailed deer, elk, and occasionally moose. This fact, combined with the fearless manner in which they have been observed competing with wolves and bears for carcasses, has earned the wolverine the title of "nature's most ferocious animal."

Incredible feeding behaviors aside, the most impressive aspect of the wolverine might be its propensity for movement. With massive, snowshoe-like feet, wolverines can move quickly and gracefully over snow-covered alpine environments. Case in point: a wolverine collared by researchers near Jackson, Wyoming, once traveled to Pocatello, Idaho, (a distance well over 100 miles) and back in under three weeks. Apparently not tired of life on the road, he later made another 100+ mile trip southeast to Wyoming's Wind River Range, then took a detour to the Salt River Range on the Wyoming-Idaho border before returning north to his home.
A wolverine family roams the backcountry of Glacier National Park

Don't let this deceive you; wolverines aren't wanderers, rambling through the mountains without direction. Rather, they are animals with massive home ranges, sometimes greater than 200 square miles, living in very low densities. In the odd event that they do manage to run into another wolverine and develop a romantic interest (which will become a lifetime partnership), the female digs a large den in deep snow in winter before giving birth to a litter of two to three in early spring, which the family will occupy until late spring/early summer. Thus, the presence of deep snow, both for movement and denning, is a critical part of wolverine life history.

It is these strict habitat needs--particularly the need for stable snowpack--that now have prominent scientists and researchers discussing whether the animal warrants the heightened protection of Endangered Species Act listing. Some climate models predict that suitable wolverine habitat will decrease by almost two-thirds before the end of the century if warming and reduced snowpack trends continue. It is a particularly damning revelation for the wolverine, whose population is just beginning to recolonize habitat in the lower 48 after near-extirpation, and now numbers somewhere between 250 and 300 individuals. In 2008 and 2009, a few ambitious wolverines wandered as far south as Utah and Colorado, the first time they have been observed in either state in nearly a century. Now, the strides being made by wolverines to re-establish themselves in the West are in danger of being nullified by climate change.

If ESA protection is granted to the wolverine (a decision that will be made in about three months time, once the comment period closes), researchers would be allowed to introduce an experimental population in Colorado, a region which offers plenty of suitable habitat, yet due to connectivity issues, has not been naturally recolonized. It is unknown if similar reintroductions/translocations would be permitted in other areas of the western US. Due to the nature of wolverine habitat (high, cold, rocky, dry places), ESA listing would likely have little economic impact, though it would certainly put an end to Montana's trapping season, which currently allows for the taking of five animals annually. It is worth noting that the 2012-2013 season was suspended by a U.S. district court in anticipation of the ESA listing proposal.

While the future of the wolverine is uncertain, there is little doubt that Montana will be an important part of that future. Today, roughly half of the lower 48's estimated population of 300 wolverines lives within the Big Sky state. The mountains of northwestern Montana, particularly Glacier National Park and the nearby Bob Marshall Wilderness Complex, are a stronghold for this fiery weasel. Conserving wolverines, therefore, is intimately tied to the conservation of our backyard.


26 January 2011

Wolverines: Dangerous or Endangered?


Picture a weasel -- and most of us can do that, for we have met that little demon of destruction, that small atom of insensate courage, that symbol of slaughter, sleeplessness, and tireless ,incredible activity -- picture that scrap of demoniac fury, multiply that mite some fifty times, and you have the likeness of a Wolverine.
-Ernest Thompson Seton, "Lives of Game Animals.”


The fiercest creature on earth. Demon of the North. A dangerous killer. Indian Devil. Given the wolverine’s astonishing array of sinister nicknames, it is difficult to imagine what would possess a person to acquire a wolverine and keep it as a house pet. However, in his book Demon of the North, a German animal dealer in the 50’s, Peter Krott, recounts his domestication of and affection for these elusive predators. The wolverine plays prominently in Native American mythology as an oftentimes malevolent trickster figure. In Passamaquoddy mythology, “Master Lox” or “the Indian Devil” is a wolverine.  In the popular imagination, the wolverine has come to be representative of the brutal, wild landscapes which it inhabits.  With a bear-like appearance (albeit much smaller), teeth which can crush bones and tear through frozen flesh, and the ability to outrun a snowshoe hare (see video footage here), it’s not entirely surprising that the wolverine has developed a reputation as a ferocious predator.  

Physical Characteristics
The largest member of the Mustelidae (weasel) family, the wolverine is stocky and bear-like in appearance. It has small eyes, rounded ears, short legs, and large, 5-toed feet which act as snowshoes in the snowy habitat in which the wolverine spends much of its time. Adult wolverines generally range in length from 25-35 inches and weigh 20-50 pounds. They display sexual dimorphism, with males often weighing up to 140% the weight of the females. Their fur is a dark, glossy brown, and was prized by the Inuit and fur traders alike for its frost-resistance.

Diet
The wolverine’s Latin name, Gulo Gulo, translates to glutton, denoting a voracious appetite and over-consumption but this is an inaccurate depiction of the wolverine’s eating habits. The wolverine is a scavenger and will eat anything from plants, berries, or eggs to caribou. It eats carrion (often the leftovers of other predators) but is also capable of bringing down animals several times its size when necessary. According to Daniel Mathews, in Rocky Mountain Natural History, “Biologists in the Selkirks found a 300-pound caribou brought down by a 25-pound wolverine, which must be close to the extreme size ratio a lone mammal predator can tackle.” What they don’t eat they will often spray with musk and store in a cache for later (the behavior from which the nickname “skunk bear” derives.)

Range and Habitat
Wolverines are capable of traveling prodigious distances. A lone wolverine will travel up to 30 miles in a single day in search of food. A male’s home range may be as large as 400 square miles. They live in remote, vast wilderness areas in boreal forests and tundra in Northern latitudes. The wolverine has been extirpated from much of its former habitat by the encroachment of human development.

Protection Status
The wolverine is not listed as endangered or threatened, though many wolverine advocates have been working tirelessly to achieve protection for wolverines. The potential impact of global warming on critical wolverine habitats is of particular concern. Wolverines rely on the carrion of ungulates which have fallen prey to avalanches and other winter-specific deaths, and as we continue to see milder winters, food could become more and more scarce for these scavengers.  Female wolverines are reliant upon the winter snowpack for their dens and as this snow disappears, it will become increasingly difficult for them to find suitable sites for their dens.  Additionally, a decrease in winter snow cover will fragment already vulnerable wolverine populations even further. A lack of connectivity between different populations increases the likelihood of inbreeding, and the subsequent plummeting of genetic variation and the species’ long-term survivability.

Last December, the U.S. Fish and Wildlife Service acknowledged that wolverines are endangered; however, it refrained from listing them, citing a backlog of petitions for endangered status for different species and a lack of funding as reasons for this decision. Steve Guertin, regional F.W.S. director, said, “Listing the wolverine as a designated population at this time is precluded by the need to address other listings of higher priority, it is proposed for listing when funding and workload priorities allow.” In the meantime, a study done by the Rocky Mountain Research Center and the University of Washington Climate Impacts group predicts that the wolverine’s habitat will decrease 63% by 2099.  This incredibly resilient creature might not be tough enough to survive a changing climate.