Wolverines are the essence of wilderness. High in the mountains, they lurk near avalanche paths and earn their Latin name, Gulo gulo (glutton), by gorging on half-buried animals and breaking bones with powerful jaws. They traverse deep snows with plate-sized feet and scale mountain summits so quickly it puts the world’s greatest human mountaineers to shame.
Although far from timid, wolverines are highly sensitive to human disturbance, says biologist Tony Clevenger, who’s been studying them in the Canadian Rockies for more than six years. “They’re big weasels with very fast metabolisms,” he says, “so they can’t just survive high up in the alpine on a rock; they also have to travel the valleys between those high passes.”
On a sunny day in March, I follow Clevenger into the backcountry northwest of Elkford, B.C. to check some bait traps he’d set up to hopefully attract, photograph (via motion-activated camera), and collect hair samples from passing wolverines.
It’s a non-invasive form of sampling; no animals are handled or harmed. By extracting DNA from the hair wolverines leave behind, Clevenger and fellow researchers hope to better understand these under-studied and elusive predators, and where they live and move throughout these mountain ecosystems.
We check three bait traps, and though it may be coincidence, it seems that signs of wolverine and other carnivore activity dissipate as we get closer to the well-used snowmobile trail. Even more so near the road that eventually intersects with busy Highway 3, which zigzags through southern B.C. and Alberta.
“The genetic data we collect here is scarce compared to the national parks,” says Clevenger. “Highway 3 is a barrier for female grizzly bears, and wolverines tend to be even more road-averse than grizzlies. I’d be very surprised if they’re crossing that highway.”
All those roads and trails trace the history of human settlement and development in this region – snake-like incursions into habitat that once seemed so much more remote. It makes for an increasingly perilous journey for wolverines and other species that thrive on long-range movement in their search for food and mates – a reality that’s been borne out by studies showing genetic discontinuities between wolverine populations on either side of Highway 3.
Along the rocky ecosystems that hug North America’s Continental Divide, wolverines inhabit high-alpine, snowy regions that thin out the farther south you go. And like other wide-ranging species, they depend for survival on a patchwork of protected areas along this mountainous stretch, dubbed Yellowstone to Yukon, and on the wildlife corridors that link them together.
“In the U.S. Rockies particularly, those mountain ranges are like little islands,” says Jodi Hilty, president and chief scientist of the Yellowstone to Yukon Conservation Initiative. For the small number of wolverines that live south of the border – estimated at only 300 – staying connected with larger populations in Canada is essential. “Those interactions introduce new genes and new individuals into each population, and make them more resilient to disease and climate change,” she says.
That need for trans-boundary connectivity explains Clevenger’s focus for his 2016 wolverine survey on an 8,200-square-kilometre region just north of the U.S.-Canada border, encompassing B.C.’s Elk and Flathead Valleys and connecting Canada’s big mountain parks with Montana’s 400,000-hectare Glacier National Park. “This is a critical piece of geography,” says Clevenger, since it’s one of only a few corridors where wolverines can move between the two countries.
In earlier surveys in national parks – Banff, Yoho and Kootenay – Clevenger found relatively healthy wolverine populations. But in the unprotected areas of southern Alberta and B.C., he says a range of factors impede wolverine movement and hence gene flow, including extensive highway traffic, forestry, oil and gas development, and rampant snowmobile and ATV use.
Adding to those issues, climate change further fragments dwindling wolverine habitat. Recent studies have shown that wolverines live primarily in areas where snow persists late in springtime, since females rear their young in deep snow at high elevations. As warmer temperatures melt snowpacks earlier each year, it reduces both denning habitat and availability of viable movement corridors.
If wolverines lose their connectivity across mountain landscapes, Clevenger warns, it would lead to genetic isolation and an ultimate population crash. “It could take six or seven generations, maybe longer,” he says, “but eventually it would happen.” Although his research raises that alarm now, he says the more immediate concern is protecting current populations, and minimizing individuals lost to trapping, roadkill and other human-related mortalities.
The good news is that wolverines have already rebounded once from the brink. After being eradicated from the U.S. Rockies in the early 1900s due to excessive trapping, hunting and poisoning efforts, wolverines recolonized the area over the last half century, moving south from Canada – a history that perhaps best illustrates the vital importance of trans-boundary connectivity. “It’s the right scale for us to be working,” says Clevenger, describing the big-picture focus of his research. “We’re mapping out the important habitat and corridors that wolverines need to survive long-term.”