On the Edge

Wolverines, long admired for their ferocity and canniness, are so elusive that few people have even seen one. Now biologists are racing to find them before trappers do.

Springtime high in the Rockies, where the calendar reads May 9, but it’s snowing in rattling bursts of graupel. After snow-shoeing for hours up a tilted, twisted drainage in Montana’s Gallatin Mountains, south of Bozeman, I emerge into the headwaters cirque and stagger to where a cluster of researchers, led by Wildlife Conservation Society biologist Bob Inman, are gathered around three holes bored into the snow.

Nobody seems to think the climb has been exhausting except me. Wolverine researchers are freakish in their ability to cover punishing vertical terrain—and yet their subject routinely eludes them. “A wolverine will climb up an avalanche chute, climb up over a cornice, belly-slide down the other side, and keep running,” says Tony McCue, then a field biologist on the crew. “They’re so fast in covering their habitat, we just can’t catch up with them unless they’ve decided to stop.”

Inman, McCue, and the rest of the team fervently hope a wolverine has stopped somewhere under our feet. Even after the grueling ascent, the biologists seem energized by the knowledge that we’re standing around the entrances to one of only a few wolverine natal dens ever discovered in the United States.

It’s as close as I’ve ever been to wolverines, closer than all but a handful of people will ever come to one. Wolverines, the largest terrestrial member of the weasel family—a male weighs 30 to 35 pounds, an average female about 20—inhabit such austere territory in such meager numbers that even people who spend their entire lives exploring high-mountain backcountry may never see one.

Human encroachment of another sort could render the embattled mammal all but invisible: Trappers and outdoor recreationists, such as snowmobilers, might provide the one-two punch that limits current wolverine population growth. After spiraling to near extinction by the 1920s, wolverines in the Lower 48 managed a dramatic recovery in some states from the 1960s to the 1980s, aided by bans on wolverine trapping in most places. Today small, genetically isolated populations hang on in Montana and northwest Wyoming, central Idaho, and the Cascade Mountains in Washington. Still, the animal remains highly sought by trappers.

In 2003 conservation groups petitioned the U.S. Fish and Wildlife Service to review studies and consider the wolverine for protection under the Endangered Species Act. Under the influence of now-disgraced Interior Undersecretary Julie MacDonald, the agency found that there was not enough information about the animal to act on the request. (A federal judge ruled in 2006 that the agency’s finding was “in error,” and a formal review is now under way by court order.)

Although the agency’s reasoning seems circular, it’s true that until recently wolverines were North America’s least-studied large carnivore. Before the 1990s, mythology for the most part substituted for science. In an early account, wolverines were such gluttons—their Latin appellation, Gulo gulo, means glutton—that they gorged themselves on prey, then forced their bodies into tight gaps between trees and squeezed the flatulence from their bowels so they could eat more. In Native American lore, the wolverine was a conduit to the spirit world and often served in the role of trickster-hero. Fur trappers called the wolverine the “devil bear.”

Mention a wolverine to anybody who knows just a little bit about wildlife, and you will almost certainly hear about ferocity, and maybe a story about how these animals win battles against grizzly bears 10 times their size. This, too, is largely myth. Inman knows two of his collared wolverines have been killed by black bears, and another researcher described seeing a coyote snatching a wolverine by the tail and flipping it into the air repeatedly, as if toying with the animal.

Although there is evidence of wolverines killing moose trapped in deep snow, their bone-crunching jaws and powerful shoulders and neck—ideal for digging—are built to scavenge. A foraging wolverine can smell carrion, like a bighorn sheep or a mountain goat that starved or perished in an avalanche, buried under six feet of snow from a considerable distance. Because a female wolverine must forage for scarce carcasses, kits learn about high-country travel early in life. About nine weeks after giving birth in a natal den—an average of two or three kits is common—a female wolverine begins to move her kits to a series of temporary dens she digs closer to sources of food.

Inman and McCue suspect the den we’ve reached in the Gallatins is a natal one. McCue happened on it a few days earlier when, during a routine survey, he cut tracks made by the female and one kit and followed them to the entrances. For Inman, a lean man with a sturdy chin cupped in a reddish brown beard, this is a big moment. Partway through a scheduled decade-long study, Inman is trying to capture a kit to monitor for the project. This year none of the eight radio-collared females in his study group denned. The den we’ve hiked to is his only shot at digging out a kit until next winter. But a fresh blanket of snow combined with the absence of telemetry beeps makes knowing where—or even if—a female wolverine and her kit are huddled beneath our feet pure guesswork.

The plan is to excavate until a crew member can belly-crawl in and snatch a squalling six- to eight-pound kit, then surgically implant it with a radio tracking device about the size of a AA battery. It’s an intrusive procedure, Inman admits, but other studies have demonstrated its relative safety for the young wolverine. So little is known about the wolverine in the United States that successfully implanting a kit today could advance the state of the science significantly.

Two hours of digging in 10-foot-deep snow reveals a multi-layered maze of tunnels extending across a 90-by-150-foot stack of avalanche debris. An exasperated Inman calls off the dig. “Even if she’s in there, we’d never find her today,” he says, a soft Tennessee accent tracing his disappointment.

His crisp blue eyes lift to the band of cliffs rimming the cirque, lipped in 20-foot blue cornices. “If an adult wolverine was standing here and wanted to go up and over that ridge,” Inman asks McCue, rhetorically, “what would it take her, 10 minutes? Fifteen?”

It would take us until tomorrow, and by then she’d be somewhere else.


Jim Halfpenny, a noted tracker and naturalist, once told me he knew a trapper who has, over his lifetime, killed 30 wolverines in southwestern Montana. That would be a remarkably destructive feat—one man wiping out a significant number of the wolverines born in that area in his lifetime. In the northern Rockies, fewer than 10 wolverines—a dominant male, two or three breeding females, a couple of the year’s young, and the occasional interloping male—might occupy 300 to 500 square miles or more. Trapping could take a heavy toll on such a meager population.

Jeff Copeland, a biologist with the U.S. Forest Service’s Rocky Mountain Research Station in Missoula, Montana, has been studying wolverines in the contiguous United States longer than anybody. He currently oversees monitoring projects in Glacier and Yellowstone national parks, which, together with work done by Keith Aubry, a biologist for the Forest Service, and Inman, are the only ongoing wolverine studies in the country. Another research project, in Montana’s Big Hole Valley, fizzled—at least partly because recreational trappers killed 40 percent of the animals in the study.

Copeland says both he and Inman have demonstrated that recreational trapping can have a “huge impact” on wolverine populations. “It’s pretty clear that areas that are trapped experience higher mortality,” says Copeland. “It’s not like the population can compensate for it.”

But when Montana officials publicly discuss regulations or limitations on recreational trapping of any sort, a cadre of trappers show up to shout about their heritage. At an August 2007 meeting of the state’s Fish, Wildlife, and Parks Commission, for instance, Inman testified that wolverine quotas should be cut almost in half from the current 12 to no more than seven animals taken statewide. He also offered the commissioners the opportunity to review data with him and learn why, in the case of wolverines, these small numbers matter. Swayed by the trapping lobby, the commissioners seemed concerned, then reduced the quota to 10, just two fewer than the original allowance.


Another wolverine search, another day, this time in the high mountains around Yellowstone National Park. (All of the biologists involved in this story asked me not to identify drainages we visited, for fear trappers may come looking for wolverine pelts.) This time I’m with Jason Wilmot, a tall, steely-blue-eyed man with cornsilk blond hair who works for Copeland on a study in the Yellowstone park environs. Nobody is sure how many wolverines use the park as their home range, but Wilmot knows of at least two.

He and I are checking a “lid down” signal being sent by one of the live traps—log houses six feet long by three feet wide and four feet deep, built with a trapdoor roof that slams shut once a scavenger is lured in by the frozen beaver carcasses used as bait—he’s built just outside the park. When we tilt up the lid and peer in with a flashlight, a red fox squints back at us—no wolverines for me on this day either. Which, Wilmot tells me, I should accept as par for the course.

“Wolverines are such a mystery. They exist on the edge of human understanding, even comprehension. They’re so tough and live in such extreme terrain. People have spent their whole lives in Montana outdoors and never seen a wolverine,” marvels Wilmot, who has spent a good chunk of his life studying wolverines and seen only seven when he wasn’t conducting research. “We’re still trying to find out foundational information, basic ecology. What’s their reproduction rate, what do they eat? It’s amazing to me that there’s a critter in this day and age that we know so little about.”

Above us on the steep mountain slopes, snowmobile tracks loop in parabolas, the remnants of an activity called “high marking,” in which riders drive their snowmobiles as high as they can up a steep pitch. “They’re getting in touch with nature,” Wilmot says with a twinge of sarcasm. Today’s snowmobiles are faster and more powerful than ever before, carrying riders deeper and deeper into wolverine country.

If you drew a line on a map around areas where deep snow persists late into May, you would fairly accurately describe the wolverine’s known historical range: the circumpolar tundra and boreal forests; Alaska and western Canada; the island refugia in the northern Rockies; the Cascades range in Washington and Oregon; the upper Great Lakes; and California’s Sierra Nevada range, where a long-isolated population genetically more similar to Mongolian and Scandinavian animals than their North American cousins has probably—nobody knows for sure—been extirpated. That line would also encompass some prime winter recreation areas.

Wolverines require enormous chunks of territory and travel amazing distances looking for food and mates. Using a GPS collar, Inman documented a dispersing male wolverine, M304, traveling 256 miles in 19 days. Then, after a few days’ pause, M304 rambled 140 miles in seven days—straight-line measurements that do not account for the jagged terrain he actually traversed. In the 34 months he was monitored before being killed by a trapper, M304 appeared in eight distinct mountain ranges, in three states, two national parks, and three national forests.

But Inman suspects incursions into the high country by snowmobilers, heli-ski operations—where skiers access remote areas via helicopter—and back-country cross-country skiers may have impacts on wolverine populations. Wolverine territory is remarkably short on food—an avalanche-killed mountain goat here, a starved-to-death bighorn there—which probably influences the animal’s slow reproductive rate.

“They exist at the margins of what’s possible,” Inman says. “Anything that could change that energetic balance would have serious repercussions for an animal that reproduces so slowly.”

One of Inman’s radio-collared females lives in an isolated area of the Madison Range that’s nearly overrun with snow-mobiles in winter. She happens to be one of the smallest animals in Inman’s study, at one time weighing only 14 pounds when she was captured. While Inman acknowledges that he has not yet compiled the statistical power to de-

finitively prove that winter recreation is harming wolverines, he says the case of the 14-pound female is “intriguing.”

“If there’s a problem with people snowmobiling and recreating, if wolverines are staying away from areas where these people are because they don’t want to encounter human activity, is that enough to tip the energy balance?” Inman asks.

It’s just one of the questions he and his crew of dedicated, sore-legged associates are trying to answer. Like many scarce animals in this country, wolverines adapted to fit a niche defined by inhospitable terrain and food scarcity.

We, meanwhile, don’t know whether we blithely knock loose their claw holds on survival in the name of fun. The desires of a relatively few people—snowmobilers, heli-skiers, recreational trappers—to romp around in a way they see fit may push the wolverine over its last brink before we even know enough about the species to imagine what could have saved it.