This might be a typical walk in the winter woods—if it weren’t for the bloody skinned deer leg and the bottle of skunky potion that Chris Fillingham is lugging in his backpack through Montana’s Bitterroot National Forest. While the pungent odor, a combination of garlic and skunk, would turn most stomachs, Fillingham’s quarry finds it irresistible. At least, that’s the plan. The technician is after one of the toughest and most elusive and maligned creatures of the West: the wolverine.
Only 300 or so wolverines are thought to live in the lower 48, their numbers driven down by decades of hunting and poisoning. But Fillingham knows there’s at least one rambling around this patch of the dense 1.6 million–acre forest; just a week ago he saw the telltale diagonal tracks right where we were standing, about two miles from the nearest road. Now he and the rest of the U.S. Forest Service crew—fellow technician Tanya Neidhardt and biologist Andrea Shortsleeve—are after more definitive proof. They’re putting out fresh meat and stinky goop at a nearby bait station, one of a dozen specially designed platforms they’ve erected in the southern half of the forest.
Wolverines, the largest terrestrial members of the weasel family, are in trouble out West. The scrappy scavengers—also known as “skunk bears,” “mountain devils,” and, most deliciously, “glutton,”—depend on deep, persistent spring snow for denning. As you might imagine, climate change does not bode well for the beasts. Even so, in August the U.S. Fish and Wildlife Service withdrew its proposal to list the wolverine as a threatened species. Several conservation groups have since sued to reverse the decision.
The controversy surrounding the proposal and litigation has made the wolverine-tracking project a priority, says Shortsleeve, who points out that there are several similar efforts across the region. “There are so many knowledge gaps, so much we don’t know about this sensitive species," she says. "This is a way to try to get ahead, to get more information.”
For the last two years, the Bitterroot crew went for the traditional camera-trap approach—tie a hunk of meat to a tree, spread some smelly gunk nearby, and point a motion-sensor camera in the general direction. Now in the third year of the project, the team is adding 12 setups that require the surprisingly nimble animals to go through something of an obstacle course. In search of the smelly goodness, the wolverine must climb a tree, balance on a two-by-four, and go through a box lined with two rows of alligator clips that snap shut at the slightest touch, snatching a fur sample. Then the wolverine has to rear up and stretch for the carrion hanging overhead—just out of its reach, of course.
A camera records it all, but, most importantly, it documents the distinctive pattern on the wolverine’s belly. Each individual has unique markings, “like a fingerprint,” says Shortsleeve, who adapted the new platform design from one built by Alaska biologist Audrey Magoun. The shots of the animals’ nether regions reveal quite a bit of information. “It’s an easy way to identify individuals and their sex,” she says. ”And at the right time of year, we can determine if they’re reproducing if we get a lactating female.”
“Getting that kind of information—more than just a picture of a wolverine—is especially useful,” says biologist Jeff Copeland, executive director of the Wolverine Foundation. He’s studied the animals for two decades and says that small studies like Shortsleeve’s can provide important data about where the creatures are, who’s who in the wolverine world, and whether or not they’re breeding with those from other areas.
Copeland’s main focus, however, is on a long-term project monitoring collared wolverines in Idaho and, more recently, in Wyoming. He and his colleagues are looking at how winter recreation affects the reclusive mammals. “We’ve turned wolverine habitat into a winter playground,” he says. “There are a lot more people in the backcountry in the winter, both motorized and non-motorized.” Initial results indicate that when humans are present, wolverines tend to move about more.
Those restless times might be putting additional stress on and burning valuable calories for a species that already moves around a lot. Males can have a range of nearly 600 square miles, and the stocky beasts are known to cover gnarly ground remarkably quickly. A satellite-collared wolverine in Glacier National Park once climbed the 10,400-foot Mount Cleveland, traversing the last 4,900 feet in a mere 90 minutes. “They don’t just sit on top of the mountain,” says Fillingham.
That makes tracking the animals difficult. Fillingham and Neidhardt spend the winter snowshoeing and -mobiling to remote locations in the southern half of the forest to maintain observation stations—always armed with an avalanche beacon. Meanwhile, in the forest’s northern section, Shortsleeve’s team is working with 25 volunteers, who are baiting traditional camera traps and cross-country skiing or snowshoeing in to check on them.
On this particular day, the camera trap came up empty except for some photos of startled looking deer. Disappointing, but Shortsleeve points out that even when the stations don’t capture wolverines, they often still provide intel about other secretive species. “Fishers are typically found in dense understory, and we’ve gotten pictures of them in open, burned places,” she says. They also have shots of bobcats, martins, and flying squirrels.
Fillingham replaces a desiccated deer leg with the fresh one from his pack (the carrion all comes from road kill). Then he warns everyone to get hiking. “It’s time to put the stink out,” he says, pulling out a bottle of Caven’s animal lure.
This particular scent is called “Gusto.” It’s an odor he’s become all too familiar with over the last three years. “Unfortunately,” he says, “I have to keep it in my office.”
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