Wilderness Traveler: The Wolverine

By Joshua O'Brian

I sometimes wonder what it is like to be a wolverine: traveling, always traveling over the land through all seasons, across mountain passes, thawing tundra, warm talus, chilly glaciers, through streams and spruce forests.

I sometimes wonder what goes through the wolverine mind as it perambulates the wilderness: hunger, most likely, and a growing map of the country it has seen. A wolverine tracks a social landscape, too, full of meaningful scents, territorial posession, encounters with potential mates, old acquaintenances, young drifters.

At every moment, wolverines are out there, somewhere, searching for rotting meat, marking territories, traversing dozens of miles in a day. I like to remember that, and reflect on what a wolverine might be doing during my day.

The Opportunist

Wolverines, a larger cousin to the fisher and marten, are the largest land-dwelling member of the weasel family. They make their living in a unique way, as wide-ranging predatory scavengers. Wolverine home ranges average between 30 and 250 square miles, and individuals with ranges of up to 770 square miles have been documented. Wolverines travel through immense tracts of land, always looking for something to eat.

That something to eat may be anything from ants and grubs dug out of a rotting log, to ground squirrels, grouse, berries, eggs, and especially carrion. To sustain their large (25-55 pound), but relatively slow-moving bodies, especially in the winter, wolverines have to find large ungulates like elk, deer, or caribou that have been served up to them by starvation, cold, avalanches, or other predators. In coastal areas, wolverines also scavenge or hunt sea mammals.

Imagine a forest in winter, and the search for big dead animals may begin to seem like looking for a needle in a haystack. Fortunately, wolverines are good enough at what they do that in some places, winter may actually be their "fat time."

Wolverine owe their scavenging success to a compact, powerful body capable of traveling 25 miles a day or killing a caribou swamped in deep snow, and a nose that can detect carrion up to two miles distant, or buried under three to six feet of snow. Even if a kill has been picked clean by other animals, the wolverine’s powerful crushing jaws allow it to glean what precious marrow is left in the barren bones.

Wandering With a Purpose

Foraging wolverines don’t just wander at random throughout their huge home ranges in their search for food. For example, Jeff Copeland, a wolverine researcher in Idaho, tells the story of a male wolverine that in early April of one year discovered one of his baited traps. The next year, Jeff baited the trap again, and around the second week of April, the same male returned to the trap again. The third year, the same thing happened – come early April, the wolverine was back for his annual snack! Another tale is told of a wolverine who discovered a marten trapper’s line and regularly checked it by walking along a nearby road and cutting off into the woods at each trap to see if it held a marten or other animal. Two years after the trapper had abandoned the line, the wolverine was still checking it.

In the absence of trappers or scientists, this kind of behavior may not seem to make much sense as a foraging strategy. Except perhaps in avalanche chutes, animals aren’t likely to die at the same time, same place each year. However, other kinds of food do appear with seasonal regularity: a wolverine who discovers a berry patch and returns at the same time the following year is likely to be well-rewarded. Similarly, at ungulate calving grounds or at salmon spawning beds in a shallow stream, easy food can appear with clocklike regularity.

The Evil One

The ancient reputation of the wolverine for cleverness, greed, ferocity, and outright malevolence is another testimony to its skill as a scavenger. Also known as "devil bear," "glutton," "demon of the north," "the evil one," and "he who steals furs," the wolverine’s main misfortune in its relations with humans has been to equate windfalls from heaven with windfalls from heaven that belong to people. A wolverine who raided a trapline or broke into a crucial cache, ate its fill, and then returned again and again to take and hide whatever remained very well might have seemed evil to the person who was counting on the supplies in the cache for survival. Still, as is the case with all wildlife, wolverines have always had more to fear from people than we from them.

Wilderness Refuge

Wolverines once roamed and foraged across the entire northern tier of the U.S. and down into Arizona and New Mexico. Now, populations only survive in remote Montana and Idaho mountain ranges, along with a few animals in Washington, Oregon, California, Colorado, and Wyoming. Why have they been so hard hit?

First, the wolverine’s scavenging habits, low population densities, and huge home ranges all make it vulnerable to trapping. Even today, across most of its range, trapping by humans is the number one cause of wolverine mortality. Massive predator control campaigns during the 1950s and 1960s probably killed even more wolverines through secondary poisoning than trapping did.

Second, wolverines are truly a wilderness dependent species, and have always been driven back by habitat fragmentation or loss. More than needing a particular type of landscape or vegetative cover, wolverines must have rugged, inaccessible habitats, or what a Forest Service technical report calls "remoteness from humans and human developments."

Wolverines are often the first animal to disappear when roads, agriculture, logging, oil and gas exploration, recreation, or almost any kind of disturbance invades a wilderness area. It’s a bit of a mystery why wolverines are so intolerant of human activity, but intolerant they are, which may be why they are doing so much more poorly in the Cascades than in the northern Rockies.

Ruining the Neighborhood

One theory about the wolverine’s response to human activity has been proposed by researcher Jeff Copeland: that female wolverines need undisturbed denning areas in order to raise their cubs. In Copeland’s study area in the Sawtooth Mountains of central Idaho, the females built their dens in high cirques and on remote talus slopes, presumably to avoid other predators. The tracks of a single skier were enough to make one wolverine move, with her young, to another den 12 miles away.

Even a moderate amount of disturbance, then, might make a female consider a site unsafe, and to abandon it in future years. Everything else about an area could make it apparently good wolverine habitat, but a reproducing wolverine population would be absent. Copeland worries that winter recreationists –anybody who seeks out remote high slopes, especially heliskiers and snowmobilers– may constitute a threat to denning wolverines.

What We Don’t Know Will Hurt Them

Because wolverines spend their lives in the places where we aren’t, and even there they are not numerous, we still don’t know them very well. To date, only six North American field studies of the wolverine have been done, compared to hundreds of studies on wolves or bears. Most of the time, we can’t answer the most basic questions of presence or distribution with anything other than vague guesses.

Unfortunately, our ignorance can work against the wolverine, as when the U.S. Fish and Wildlife Service in 1995 denied a petition to give the wolverine threatened status under the Endangered Species Act. Their reasoning: not enough information about their population to warrant a listing.

Lacking fuller knowledge, we should be more, not less cautious. Everything we do know says that wolverines, for whatever reason, have to have wilderness. If we want wolverines, there is no alternative but to leave them some land – lots of it, actually – in wild, rugged, undisturbed refuges. Just knowing they’re "out there" makes the wilderness seem more wild. Their loss would be immeasurable.