Understanding Wolverines
Elusive, tough and resourceful, wolverines may be our most misunderstood natural neighbor. That is getting in the way of conservation efforts for this embattled species. We meet some intrepid (and tough and resourceful) researchers who are out in the wilds to learn more before it is too late
Elusive, tough and resourceful, wolverines may be our most misunderstood natural neighbour… and that’s getting in the way of conservation efforts for this embattled species. Some intrepid researchers are out in the wilds to learn more before it is too late
Mirjam Barrueto knew she was being watched. Only 10 metres away, a wolverine peered out from beneath the brush, staring intently at her and her colleague, Cathy Gill, as they set up their study site in B.C.’S Yoho National Park. Perhaps it had smelled the rotting blood-and-guts bait Barrueto had just added to a wooden structure designed to collect hair and photos from wolverines. “It came from a few kilometres away,” says Barrueto, who while skiing home saw the tracks the wolverine had made as it beelined straight across the valley. This wolverine stuck around for only a few moments — wolverines are notoriously shy of people. But photos from trail cameras later confirmed it was a female who had lived in the valley for several years.
A two-kilometre detour is nothing for a wolverine. Their home ranges rival those of grizzly bears — hundreds of square kilometres — spanning some of the gnarliest terrain the mountains, boreal forest and tundra have to offer. From a helicopter, Barrueto has seen wolverine tracks that travel straight up through the deep snow of steep mountainsides, along ridge-tops and down to the next valley, only to ascend once more. “They live in the most inhospitable areas,” says Barrueto. “They go where most other animals don’t go.”
Well known for their tough and elusive character, wolverines also have a sensitive side. Biologists like Barrueto are discovering they don’t react well to intrusions. In parts of their southern range, these notoriously fierce weasels are struggling to co-exist with human settlement, recreation, roads and industry. As good habitat becomes harder to come by, populations are dwindling, and the gene pool is shrinking. As climate change alters habitats and further exacerbates the challenges they face, wolverine survival in these areas will depend on how human activities are managed in the mountains and forests they call home. “If society wants sensitive animals like wolverine on the landscape, then we have to give them the habitat they need,” says Barrueto.
Figuring out exactly what that habitat is, and how wolverines use it, has been the focus of intense study by Barrueto and other wolverine biologists over the past decade — and for good reason. The Canadian wolverine population is now only 40 per cent of what it was around the early 1800s. Though more recently numbers appear to be increasing in parts of the Northwest Territories, Nunavut, Manitoba and Ontario, breeding populations in a large part of their range (including Quebec and Labrador) have not recovered. Wolverines have been extirpated from Vancouver Island, while declines continue to be reported in Alberta and British Columbia. For this reason (and because more data is needed to accurately assess their status), they are listed as a species of special concern by the Committee on the Status of Endangered Wildlife in Canada.
As part of her PHD work at the University of Calgary, Barrueto is studying female wolverines in Alberta and British Columbia. Females are especially territorial, she says. While males can be fiercely protective, they tend to be more tolerant of incursions into their territories by other males. A breeding female, on the other hand, won’t move from her territory, and she won’t share. “Once she has a good territory where she can successfully breed, she’ll defend it for as long as she can.”
All wolverines are sensitive to roads, but again, female wolverines are warier than males. Montana State University ecologist Tony Clevenger and colleagues have observed this in the Rockies and in the Columbia mountains. When Clevenger looked at how wolverines were using wildlife crossing structures in Banff National Park, he found that males crossed the Trans-canada Highway somewhat readily, while females appeared not to cross at all. “From the genetics, it’s really clear that the Trans-canada Highway is a formidable barrier to dispersal and movement of the female component of the population,” he says.
Identifying and protecting areas that are important to females could benefit the entire population. Habitat conservation “doesn’t have to be a full-blown park,” says Barrueto. Other solutions include setting limits on seasonal activities like snowmobiling and returning old logging roads to natural habitat if females are avoiding them. Their low reproductive rates mean any drop in the female population threatens the sustainability of the wolverine population. Barrueto’s work will be an important piece of the wolverine conservation puzzle.
Matthew Scrafford is working a different part of the puzzle. He’s the wolverine conservation scientist for the Wildlife Conservation Society Canada in Ontario, where wolverines are provincially listed as “threatened,” at risk of becoming endangered. He hopes his research on how wolverines use landscapes with commercial forestry operations will help foresters and government develop a set of best practices for working in wolverine habitat. For example, if foresters know where females have denned and how they are using the landscape while looking after young, they may be able to avoid them until denning season is over, he says. Working together may be one of the only ways wolverine populations recover further ground to the south. While Ontario appears to have experienced a recent expansion of wolverines, they are limited to the northern part of the province.
Part of the problem is that forestry operations shift habitats in favour of wolverines’ competitors by creating open areas and young forests that attract prey species like deer and moose. As prey populations expand, the number of wolves increases. Wolves generally help wolverines by leaving carcasses out on the land for them to scavenge, says Scrafford, but when there are too many wolves, they will out-compete wolverines for prey — and prey on them as well.
Climate change may further exacerbate these problems. While moose are typically the dominant ungulate in Scrafford’s study area around Red Lake in west-central Ontario, he says deer populations can fluctuate radically. “If there are a number of mild winters, deer populations will increase. But during cold winters, the deer population is reduced considerably.” If climate change brings increasingly warmer winters, and large deer populations become more common, mitigating measures from the forestry industry may be crucial. “It’s why we need to learn specifically how the forestry industry affects wolverines and their habitat,” says Scrafford.
Scrafford also wants to work with the trapping community to reduce the number of wolverines accidentally caught in snares put out for other animals. While intentional wolverine harvest is illegal in Ontario, this bycatch could be having an effect on
the population. Trap design may be one solution. “What we want is for a snare to be weak enough so that when a wolverine pulls, the snare breaks away,” says Scrafford, “but not so weak that the target species is released.” So far, he says trappers are keen to help. “They are an important conservation partner. I don’t think you can move forward in trying to help the wolverine population in Ontario without them.”
Working with the trapping community and government regulators will be important in Alberta and B.C., too, where wolverine harvest is legal. Barrueto hopes that through her study, there will be a better sense of how many wolverines there are to help governments better manage trapping quotas. She wants what she learns to be shared with trappers so they can make informed decisions about their harvest. For example, “if they know there is a female in the area, they would know to be careful because if they take her, it may be a few years before a new female moves in and has babies.”
In the meantime, trappers may be taking too many. A new study from the southern part of Alberta and B.C. estimates that every year, over 8.4 per cent of the population dies in traps. Given the low density of only two wolverines for every 1000 square kilometres, the researchers say it’s unlikely the harvest is sustainable. “There are more traplines than there are wolverines,” says Clevenger. He and his co-authors recommend a 50 per cent decrease in trapping harvest in the area. “It’s a no-brainer on the Alberta side, where there are hardly any wolverines left north of Waterton Lakes National Park.”
Clevenger has been studying wolverines in the southern part of the Canadian Rockies and foothills for the better part of a decade. From Mount Robson and Willmore Wilderness provincial parks, south along the rocky spine of the continent to Waterton Lakes National Park, the landscape is a mosaic of protected areas, multiple roads, intense industrial activities, traplines and human recreation. It’s a good place to study wolverines in what was historically high-quality habitat but now has varying levels of human activity and infrastructure. In collaboration with colleagues from government and academia, Clevenger’s work has revealed a number of concerning trends in wolverine behaviour, distribution and genetic diversity.
It’s clear that wolverines in this part of the world fare much better in places with low levels of human disturbance. Wolverines now only occupy about 40 per cent of the places you’d expect to find them, says Clevenger, compared with 85 to 90 per cent of those places in protected areas like Banff, Yoho and Kootenay national parks. It’s not just that they use more protected landscapes, but that they are found in higher densities — two to three wolverines per 1000 square kilometres. It might not seem like a lot — wolverines always occur in relatively low densities — but some multi-use landscapes next to parks can’t support any.
Wolverines also show more diverse behaviours in protected areas than in more heavily disturbed landscapes. Work by ecologists Frances Stewart and Jason Fisher (Natural Resources Canada and Innotech Alberta, respectively) showed that while wolverines were investigating rotting beaver carcasses at their research sites in protected areas, some chose to take their time, sniff around, maybe sit for a bit. “Some of them lingered for a very long time,” says Fisher. At some point, they scaled the tree to take a nibble of the dangling carcass, but they didn’t appear to be in a hurry.” However, in areas with an active human presence, it was all business. Wolverines got in and out like there was no time to waste and they were much more vigilant in those landscapes.
While protected areas provide better habitat for wolverines, they are not immune to the influence of dwindling populations and genetic isolation. An analysis of DNA from wolverine hair samples collected from the Willmore area all the way to Montana shows that genetic diversity decreases north to south, even in areas with low human disturbance. This means that southern wolverines come from increasingly isolated populations, with fewer breeding adults. South of Banff and Kootenay national parks, genetic diversity (along with overall numbers) takes a nose-dive, and this is having devastating effects on the northern U.S. population that is thought to be reliant on Canadian migrants. “We don’t have any gene flow from the southern part of the province into the United States,” says Clevenger. “Connectivity to the U.S. is hanging by a thread in that area.”
This loss of numbers and genetic diversity is why Clevenger and his colleagues are recommending more protection around Rocky Mountain national parks. “These are important core areas for wolverines in the Canadian Rockies, and there should be a buffer around them where there wouldn’t be any trapping and there would be restricted vehicle access. We should be trying to reduce road density in those areas.”
In the meantime, Mirjam Barrueto continues to gather data. Already, she has found eight breeding females and hopes to find a dozen more across her 50,000 square kilometre study area spanning several mountain ranges. It’s gruelling work in difficult terrain across very remote areas. Not everyone could pull it off, but Barrueto seems almost as determined as her subject. She hopes her work will help wolverines have the habitat they need — for their benefit and for ours. “The more iconic species we lose, the more tame the landscape becomes. It narrows our minds and limits what we think is possible.” There’s still a lot to be learned, and she’s inspired by the animal she studies. “Wolverines just seem to take challenges head on,” she says. “They run around the mountains all year — they don’t just go to sleep like a bear.”a