Following a post earlier this week, which included a response to a short news article about a Canadian study, the supervisor of that study was kind enough to contact me to clarify some of the goals and methods of the work. I’m reposting those comments here so that they are highlighted and so that the regular readership of this blog, which I know is primarily interested in the science, is sure to see the comments. I appreciate this conversation and hope that it will be on-going, because this issue of how to sort out habitat selection and anthropogenic influence is key to understanding how we can better protect wolverines:
Rebecca, thanks for all of your hard work on this blog, I always enjoy it.
I’m Nikki Heim’s supervisor and the principal on this research. Your question is key: “…are wolverines relatively abundant inside these parks and scarce outside because they are avoiding humans and selecting for protected areas, or because they are tundra animals in a landscape where tundra is only found at the high elevations inside the parks?”.
The goal of the East Slopes Predators project was to get at this very question. Kananaskis Country (KC) Alberta, where wolverines were scarce, is very nearly as fearsomely rugged as adjacent Banff National Park (BNP), where wolverines were dense. KC has plenty of high-alpine habitat, and prior to 2 decades ago, KC was a provincial icon of wolverine habitat. The major difference between the two (and the reason we selected it for study) is the current magnitude of anthropogenic features: KC has plenty, BNP has comparatively little.
Critically, our statistical analysis does not conflate anthropogenic footprint and topography – which are not correlated in this study area – but rather parses these two apart. The clear result is that even after accounting for topography and spring snow, anthropogenic footprint plays a key role in explaining wolverine distribution. We obtained this same result in Fisher et al. (2013) from Alberta’s Willmore Wilderness. We now have data on 90+ wolverines, from an area over 20,000 km2, which support the conclusion: even after accounting for topography and persistent spring snow, anthropogenic features best explain wolverine distribution in this vast region.
I wonder: are wolverines a mountain & tundra species? They currently live throughout the boreal forest. Historically, they occurred throughout the great plains and mixed transitional forests stretching south of the Great Lakes. Hudson’s Bay data shows hundreds (and more) of animals were taken from these regions very early on in colonization, long before scientists started examining their distribution. Some analyses from the US include these historical data, but not in Canada, where most wolverine were harvested. We are left with a “shifted baseline” to measure against, a common problem in fisheries but less acknowledged in terrestrial ecology.
I agree there is danger in conflating topography, persistent spring snow, and anthropogenic footprint, but it cuts both ways. Across the continent, persistent spring snow remains where anthropogenic footprint has been least, yet topography and spring snow remain the dominant theory. I wholeheartedly agree that more research is needed to tease apart these two conflated factors, before we settle on snow as an exclusive mechanism.
Very best regards,
Jason T. Fisher, BScH MSc PhD
Senior Research Scientist – Wildlife Ecology
Alberta Innovates – Technology Futures
School of Environmental Studies, University of Victoria
With regards to the comments, I have only one point of clarification – as I understand it, there is no evidence that wolverines ever occupied the regions south of the Great Lakes within historical times. Unfortunately the Hudson’s Bay Company’s archives are not yet digitized, so I haven’t seen these trapping records myself, but the American researchers who’ve worked with those records have told me that the records come from trading houses through which pelts passed. Information about the locations of individual pelt origin are not available. This means that wolverine pelts coming through a trading post in, say, Michigan, could easily have come from much further to the north or west. I run into this issue when I do my work in Mongolia, as well; I record a lot of pelts in Ulaanbaatar, but that doesn’t mean that there are wolverines running around the city. It means that that’s where marketable goods from the countryside accumulate and are redistributed to buyers. I also record a number of pelts in locations way out on the steppe, but when questioned, the herders who possess those pelts make it clear that they were generally obtained in more forested or higher elevation areas far from where we sit talking about the pelt in front of us. In the rare cases where they’ve been obtained from the local environs, the species is never referred to as resident; it’s always a case of “it wandered into a wolf trap and this is the only time I’ve seen this animal in 60 years of living here.” Without this detailed contextual information, however, someone 200 years from now, looking only at where I obtained pelt samples, might conclude that wolverine range included places that it actually doesn’t. Maybe there were wolverines in Michigan and the Great Plains 200 years ago, but the trapping records are not, as I understand it, reliable records for determining historical range.
That said, there’s no doubt that there has been range contraction since European colonization, and we are dealing with shifted baselines for just about every species and ecological process that we are trying to understand. The very best book I’ve read about the broad strokes of this process is William Cronon’s “Changes in the Land,” and I highly recommend it for people who want to consider the way in which economic, religious, and political philosophy can alter entire ecosystems in ways that are almost invisible to and unconsidered by subsequent generations – the way that, in essence, thoughts end up shaping landscapes. We’re dealing with the consequences of that to this day.