From "The Wild Bunch"
The Wolverine
To some people, the largest land-dwelling member of the weasel family looks a little bit like a 25 - 40 pound skunk. To others, its brown fur and stocky body reminds them of a small bear. The wolverine, or "skunk bear" as it is sometimes called, doesn’t really look like any other animal on the continent. Of all the forest carnivores, the wolverine is the least known, and most mysterious.
Wolverines make their living by being wide-ranging, predatory scavengers. The home range used by a single wolverine can be anywhere between 30 and 250 square miles, and researchers have reported some individuals with home ranges of up to 770 square miles!
Wolverines are always traveling, often over huge expanses of land, and they’re almost always looking for something to eat."Something to eat" for a wolverine can be anything from the ants or grubs it finds by tearing open a rotting log, to mice, grouse, and ground squirrels – a range of live foods similar to those used by fisher and marten, but with an emphasis, especially during the winter, on one other item – carrion. To sustain their larger energy needs, wolverines rely on being able to find large ungulates like deer, elk, and caribou that have been served up to them, ready-to-eat, by starvation, cold, disease, avalanches, or other predators.
Many characteristics of the wolverine combine to make them such successful scavengers. They are persistent travelers, able to move more than 20 miles in a day through rough terrain and deep snow.
The wolverine’s strength is legendary, and many exaggerated tales of their abilities have been told. The truth is as impressive as the fiction: wolverines are able to carry a 40-pound beaver carcass or drag off an entire deer carcass, should the need arise.
The bones in a wolverine’s skull are heavy, and their large teeth and powerful jaw muscles make it easy to crush large bones and grind frozen meat. Even if a carcass has been picked over completely by other animals, wolverines can get nourishment from the marrow left inside the dry bones.
We don’t know if wolverines locate carcasses by smell, by remembering the location after having seen it before snowfall, or by following an earlier scent marking of the site. Whatever the method, they are remarkably good at what they do.
Wolverines often will travel the same route while making the rounds of their territory, and they have an excellent sense of space and direction. They are well known for following traplines and taking whatever animals they find caught in the traps. Idaho Fish and Game researcher Jeff Copeland tells of a male wolverine who visited his baited research trap three years in a row in early April to get his annual snack.
Although traps aren’t the most reliable sources of food, many other kinds of food do appear with seasonal regularity. A wolverine that discovered a berry patch one year would probably be rewarded the next year with another round of high-energy fruit. And at ungulate calving grounds or salmon spawning beds in shallow streams, high-protein, easy food can appear with clocklike regularity, year after year.
Because of its skill at locating and taking food, the wolverine has been the victim of some serious name-calling. Trappers called the wolverine "devil bear," "demon of the north," and "devil beast." Native people’s names for the wolverine included "evil one," "tough one," and "he who steals furs." Even its scientific name, Gulo gulo, translated from Latin, means "glutton glutton."
Of course, wolverines are not actually malicious or evil; they’re just making a hard living in an unforgiving landscape. People who have raised wolverines in captivity speak of their gentleness, curiosity, and playfulness. The reason for all the bad press is that wolverines don’t distinguish between windfalls from nature, and human possessions that seem to be windfalls from nature.
In reality, people have been a much greater threat to the wolverine than it is to us. Wolverines’ wide travels and their scavenging habits make them vulnerable to trapping – even when the traps are set for other kinds of animals.
Because they are such accomplished scavengers, many wolverine’s have died from "secondary poisoning." During the government’s campaign to exterminate predators in the early to mid part of this century, wolverines found and ate the bodies of coyotes, wolves, or bears that had been killed by poison baits, and then died themselves from the leftover poison in the tainted carcasses.
A basic requirement of good wolverine habitat is the presence of healthy, diverse ungulate populations, whose die-off during the winter keeps wolverines fed. The greatest numbers of wolverines are found in areas that have healthy populations of other carnivores, like wolves, who help produce a steady flow of carcasses for the wolverine to scavenge. It’s a dangerous trade-off, however. Wolves are known to hunt, and kill, wolverines.
But as much as abundant prey and the presence of other predators, wolverines need what a U.S. Forest Service technical report called "remoteness from humans and human developments." Other biologists have pointed to the wolverine’s need for "large, isolated tracts of wilderness," "large, mountainous, essentially roadless areas," and "rugged and inaccessible habitat."
In other words, while martens and fishers are forest-dependent species, wolverines seem to be wilderness-dependent species. When we disturb a wild area, wolverines can be the first animals to disappear.
Exactly why wolverines need remote, undisturbed areas has long been a mystery. One recent theory, put forward by Idaho researcher Jeff Copeland, is that females are very sensitive to disturbance when they are raising their kits. A wolverine den can be found at the base of a slide. This location is typical in the Sawtooths, where female wolverines build their dens on high elevation talus slopes. Female wolverines dig through the snow covering the rocks on these open slopes to the spaces between large boulders, where they are able to make a safe, sheltered den. The mothers care for the young for about 8 months, until they’re fully grown. Then, at least in the Sawtooths mountains, the youngsters often travel with other relatives up to the age of about 14 months, presumably learning from them where and how to find food, and gaining the experience it takes to be a successful wolverine.
High cirques and talus slopes are normally about as isolated and undisturbed a habitat as a protective mother could want. Unfortunately, more and more people, from heliskiers to snowmobilers to cross-country skiers, are also searching out the same highcountry slopes as the wolverines need for rearing their young. When a group of noisy people and/or machines pass near a wolverine den, the mother may evacuate, and move the kits to a new den. This takes precious time and energy for both the mother and her kits, and may cause the female to abandon the den site for good.
We don’t know nearly enough about wolverines to understand how they are affected by our activities. There are only five sites in all of North America where wolverine field research has been done. Biologists can tell us some things about how much wolverines weigh, details about their physiology, and some general information about how they live, but not much is known about how all the parts of the"skunk" bear add up to the fiercely strong and capable wilderness traveler we call the wolverine.
Its fate is in our hands. Almost any human activity, especially winter recreation, in wild, remote areas, seems to diminish the quality and security of wolverine habitat. More than any of the other forest carnivores, wolverines need large, undisturbed areas as refuges from human disturbance.
Saving a place for wolverines requires that we humans are big enough to give them the space they need to survive.
wolverine | forest | slideshows
