Cantankerous Carnivore: On the Trail of a Wolverine

Ongoing studies by a handful of field biologists are key to bringing back the elusive wolverine, once nearly extinct in the continental United States

05-01-2007 // Kurt Repanshek

Wandering the western lip of the Greater Yellowstone Ecosystem, possibly on a foray from one side of the Teton Range to the other, a wolverine met its fate. Swept away by an avalanche that tumbled down the gray, serrated flanks of Cascade Canyon in Grand Teton National Park, the animal's passing would have gone unnoticed if not for a radio collar wildlife biologist Bob Inman had fitted around its neck.

"That was our first mortality," recalls Inman, who with his wife and fellow wildlife biologist, Kristine, has been tracking wolverines in the western half of the sprawling Yellowstone ecosystem since 2001. "We don't know whether the wolverine triggered the avalanche, or whether it was just in the wrong place at the wrong time."

Indeed, outside of folklore, very little is known about wolverines, period. A circumpolar species native to boreal, subalpine and alpine regions of Asia, Russia, Europe and North America, Gulo gulo once roamed from Maine west to Washington and south along the Rocky Mountain spine into northern New Mexico. By 1920, however, the animal was nearly extinct in the continental United States, a victim of poisoning campaigns and heavy trapping for its fur. Though some populations have rebounded over the past few decades, the wolverine's full recovery is hindered by habitat loss to development, expanding winter recreation and possibly climate change.

Citing such threats--along with potential genetic problems caused by small, isolated populations--conservationists warn that the wolverine may still vanish from the lower 48 states. Yet efforts to get the animal protected under the Endangered Species Act (ESA) have been thwarted by inadequate information--a critical gap that ongoing research, including the Inmans' work for the Wildlife Conservation Society, will help to fill.

With adult males weighing roughly 30 pounds, wolverines are the largest terrestrial members of the Mustelidae family, which also includes weasels, badgers, skunks and otters. Stoutly built, the wolverine has a head vaguely resembling a bear's: broad and round with small eyes and short ears. Oversized feet help the animal maneuver quickly over snow.

During the heyday of the fur trade in the late 1800s and early 1900s, the wolverine achieved near-legendary status among backwoodsmen for its bulldog's disposition and tenacity to survive under harsh conditions. Wolverines were known for raiding traplines, breaking into cabins to forage trappers' provisions, even standing up to grizzly bears ten times their size.

Yet wolverines are like ghosts--often talked about but rarely seen. They roam remote, high-elevation landscapes in densities as low as one animal per 50 square miles and trek home ranges of up to 500 square miles. Not surprisingly, they are difficult to study. For that reason, "this is an animal that hasn't had enough attention until recently," says Tim Preso, a Montana-based attorney for Earthjustice, a nonprofit organization that last fall won a case against the U.S. Fish and Wildlife Service, forcing it to evaluate scientific data on wolverines to determine whether the animals deserve ESA protection.

Fortunately, such data are multiplying. Like the Inmans, U.S. Forest Service biologist Jeff Copeland has been conducting long-term studies of wolverines, first in Idaho and currently in Montana. Among recent findings are that wolverines live primarily at or close to treeline, are mainly scavengers and are polygamous--males usually mate with several females. Females, which typically give birth to one or two kits, prefer den sites on north-facing slopes, where they dig down through snow pack covering boulder fields or where the jumble and tangle of avalanche debris has piled up.

Yet lack of solid population data continues to thwart the species' conservation. While biologists believe there may be as many as 19,000 wolverines in western Canada and another 20,000 in Russia, the animal's numbers in the continental United States may be as low as 500, the majority in Montana, Wyoming, Idaho and Washington. To find out how many inhabit the 18 million-acre Greater Yellowstone Ecosystem, Copeland and Yellowstone National Park biologist Kerry Murphy have stitched together a network of nearly three dozen log-built traps in the eastern half of the ecosystem. Now in the second year of a five-year study, the scientists hope their results will help land managers make decisions on activities such as logging, mining and backcountry skiing in areas deemed critical wolverine habitat.

Other mysteries about the species' biology could hamper such decision-making. Critical unknowns include how wolverines survive low population densities, how they react to human intrusions, and how they overcome high mortality rates--in Glacier National Park, five of six wolverine kits Copeland outfitted with transmitters never made it to maturity. "We're just beginning to try to understand what factors regulate populations," he says. "Is it human factors, natural factors? If we don't understand that, we don't know how our activities influence these animals."

Kurt Repanshek is a writer based in Park City, Utah.

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