BANFF – Despite their fierce and ferocious reputation, wolverines might not be so tough after all.
New research in Scientific Reports on Oct. 24 shows wolverines in and outside Banff, Yoho and Kootenay national parks are in steep decline, most likely due to a combination of trapping outside park boundaries, the impacts of hordes of people recreating in the parks, and climate change.
Using photos from remote cameras throughout the parks and DNA samples collected from wolverine hair at baited trap sites, researchers found that wolverine numbers had dropped 39 per cent overall since 2011 – or an average decrease of 7.5 per cent a year.
While protected areas like national parks are important in wildlife conservation, and population density is higher inside the national park borders, the research team, which includes two Parks Canada ecologists, found wolverine numbers have been dropping both in and outside the parks over the past 10 years.
“I had the expectation that the numbers were probably stable, so I was pretty surprised when we realized how bad it is,” said lead researcher Mirjam Barrueto, who is a PhD candidate at the University of Calgary.
“The numbers have been going down, and that’s both the actual numbers but also detections on the cameras, which is pretty troubling.”
From 2011 to 2020, researchers studied population trends across a 14,000 km2 protected area in Banff, Yoho and Kootenay national parks as well as non-protected habitat in neighbouring provincial lands in British Columbia and Alberta.
For the whole study area, the estimated number of wolverines was 54 individuals, including 25 females, in 2011 and 32 individuals, including 15 females, in 2020.
In the three national parks, the population estimate was 34 individuals in 2011 and 20 in 2020, while for the unprotected areas outside the parks, the estimate was 20 individuals in 2011 and 11 in 2020.
Wolverines are resilient, yet sensitive to human disturbance and prefer deep snow to raise their kits, to keep them warm and safe from predators.
“This makes them vulnerable to climate change,” said Barrueto.
As for trapping pressures on provincial land surrounding the protected national parks of Banff, Yoho and Kootenay, 59 wolverines were reported harvested in the 106 traplines intersecting the study area between 2010 and 2020.
Combining B.C. and Alberta numbers, the mean overall annual harvest rate in the study area was 13 per cent.
Researchers say some of those rates are likely underestimated as no harvest data from Alberta was available to researchers in 2018-20, and because trapping reporting compliance rates can be low.
“The absolute number of wolverines getting trapped is not very many, but the issue is having so few animals on the landscape to begin with,” said Barrueto said.
“If you accidentally trap two or three females in one year, you wipe out a lot of the new generation… it doesn’t take much to have an impact.”
The research also looked at how increasingly busy national parks and recreation activities are impacting wolverine trends.
Parks Canada visitation numbers for Banff, Yoho and Kootenay national parks combined grew by 29 per cent from 4.13 million visitors in 2010 to 5.35 million visitors in 2019.
In winter and spring, the most popular recreational activities within the national parks are backcountry skiing, front-country skiing, snowshoeing, ice-climbing, mountaineering, and hiking. Outside the protected areas, activities include snowmobiling, cat- and heli-skiing.
The research found that wolverine density and detection decreased with recreational activity in the parks.
Barrueto said if animals become stressed or avoid otherwise suitable habitats, survival and reproduction are affected.
She said that potentially can lead to population-level effects, including decline of a species.
“If we have too many stressors on the landscape – that’s what we believe is happening within the parks because they’re so busy – then it’s difficult for the females to be successful in reproduction,” she said, noting that is made worse by trapping rates outside the parks.
Barrueto said the study indicated as few as three groups every two weeks was enough to elicit a negative response.
“Some wolverines might still run through even if there’s people, but just that threshold is quite low,” she said.
“I am a recreationist myself and I would have thought it would take more people to show an impact, so that was a little bit concerning.”
In contrast to the first survey in 2011-13, researchers recaptured the same adult females each year between 2018 and 2020 with the potential exception of one new female.
The study suggests this is a pattern consistent with high adult survival, but low recruitment, indicating that reproductive rates may have decreased.
In addition, the human use data that was analyzed was from winter and spring, before weaning, when reproductive females are considered most vulnerable to disturbance.
In summer, after weaning but before independence, juvenile wolverines continue to depend on their mothers for food to sustain their rapid growth.
Barrueto said levels of summer recreation in the study area are even higher than those of winter recreation.
“Resulting disturbances of female wolverines might impact their physical condition as well as other factors such as hunting success, which could impact their reproductive success,” she said.
Jon Stuart-Smith, Parks Canada’s acting manager for the integrated land use planning and policy section in Lake Louise, Yoho and Kootenay, said it will take some time for managers to evaluate the research, but studies like this are important and feed into the management planning process.
Under the new park management plans, he said Parks Canada will refine the grizzly bear habitat security model to better consider habitat importance for a range of sensitive or wary species, noting it is assumed the needs of many wildlife species will be met when long-term needs of grizzly bear populations are met.
Specifically, he said the new management plan for Kootenay National Park identifies that Luxor Pass trails will be re-classified as wilderness routes and train maintenance will be discontinued to reduce human disturbance in key connectivity corridors.
“We added an environmentally sensitive site at Luxor Pass and this was added because of its importance as a wildlife corridor,” he said, noting it links the Kootenay Valley to the Columbia Valley.
Stuart-Smith said remote wildlife cameras have shown this is an area used by wolverines over the past few years.
“I think by changing this designation, we’re basing it on science that we’re seeing that wolverines are using this habitat and it will be of benefit for them,” he said.
Officials with the Yellowstone to Yukon Conservation Initiative, which helped fund the study, said parks and protected areas alone are not enough for species to do well, and that improving, not just maintaining connectivity in and out of park boundaries, will be the key to help wolverines in the coming decades.
Jodi Hilty, president and chief scientist at Y2Y, said effective conservation needs to look at multiple effects and across broad scales and borders given the rapidly changing landscape and increasing human activities.
“What this particular study shows is that while protected areas are important, many of our protected areas aren’t big enough for animals like wolverines to sustain populations,” she said, adding wolverines are a quintessential Y2Y animal.
“We have to carefully think about management in an ecological network, meaning within protected areas and how those protected areas are connected across the rest of the landscape, and that only if we do that well will species like wolverines be able to persist.”
With the wolverine being considered ‘data deficient’ in Alberta, Hilty said the study suggests the province of Alberta should urgently take a look at the status of wolverines in Alberta.
She said the legal harvest was banned in the BC Kootenay boundary region in 2020 based on strong evidence trapping was having a negative effect on the already low numbers of wolverines in that area.
“If we want to sustain wolverines across this region, we probably need to think about that a little bit more broadly,” she said.
The research was initiated, in part, because of a 2018 listing of wolverine as ‘a species of special concern’ by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). This ranking reflects their low numbers and slow capacity to recover from population declines.
The researchers on the study, which also included Parks Canada’s Anne Forshner and Jesse Whittington, along with Tony Clevenger, a local wildlife scientist, and Marco Musiani, a professor in the department of biological sciences at the University of Calgary – say this indicates that management information and action are required to help prevent the listed species from becoming threatened.
Barrueto said the results show even within protected areas, surprisingly steep declines of species at risk can occur virtually unnoticed if key conservation concerns are not identified and addressed.
“If we keep doing what we do, we know where they’re headed,” she said.
The full paper can be found at: https://doi.org/10.1038/s41598-022-21499-4.