Wolverine Birthday Contest, and News Briefs

Wolverine Birthday is coming up on February 14th. This is the symbolic birthday of wolverine kits around the world, although in reality, of course, wolverine births range from January to March. Valentine’s Day makes a good reference point, though. I admit to a certain bias, but the birth of wolverine kits seems way more interesting than a fat little cupid and some chocolate. So to encourage Gulo fans around the world to broaden the celebration of love to include love for all species, I’m challenging readers to come up with ways to celebrate Wolverine Birthday in addition to Valentine’s Day. I’ll be hosting a Wolverine Birthday Party, which will include only foods that wolverines eat. Salmon, elk, and berries will be on the menu, and we’ll have a screening of Chasing the Phantom for an audience that hasn’t seen it before.  If you are also celebrating Wolverine Birthday, let me know how. You could even combine the two holidays, for example by creating a wolverine dinner date – climb or ski to the top of a snow-clad peak, and dig a week-old elk haunch out of the snow (only try this with someone you’ve been seeing for a while, and only if they have a sense of humor.) Or maybe just ski in wolverine habitat and see if you find any tracks. I leave the creativity to my readers. If you do decide to do something, leave a description of the event as a comment. The most creative endeavor will win a piece of original wolverine artwork. You have until February 21st to post your story.

In wolverine news, the most recent update for the Central Idaho Wolverine and Winter Recreation study is now available. The project is in the middle of its third field season, after two highly successful years collaring wolverines on the Payette, Boise, and Sawtooth National Forests.  Their rates of trapping success, particularly of denning females, leaves me envious and in awe. I haven’t participated in this project, but I’ve kept track of it from afar, and I am continually impressed not only with the number of wolverines that they monitor, but also by the fantastic support of the recreation community and local businesses. The report includes a couple of great images, including one that amply illustrates the use of sub-snow downfall at a denning site.

The tracking workshop hosted last week by Adventurers and Scientists for Conservation and Wild Things Unlimited seems to have been a success; they found tracks and collected DNA, reaffirming that citizen science can be valuable to research efforts. It was inspiring enough for a post and description by one enthusiastic participant. Wolverines are converting people at a pretty rapid clip, which provides an opportunity (for awareness-raising, for conservation, and for research) but also a potential liability (one of these days, I’ll get around to writing about the way in which charismatic species are the fossil fuel of the conservation movement….)

Canadian papers are picking up a story – three months after the fact – about a wolverine using a highway overpass in Banff National Park for the first time (these overpasses are landscaped and pretty posh, as far as wildlife crossings go.) Nine wolverine crossings have been recorded at nearby underpasses, but this is the first use of an overpass. The underpass crossings seem to have picked up over the past two years.  In the article, researcher Tony Clevenger states:

“We don’t know a lot about wolverines, but we do know there’s a learning curve, which we’ve seen for grizzly bears and black bears as well…Perhaps this is what we’re seeing, that it’s an initiation of a learning curve, that they’re starting to figure out what these things are and starting to use them.”

This made me start to think. We’ve “seen” wolverines following other wolverines around in GPS and telemetry data, and  scent marking might help wolverines navigate the landscape. If wolverines follow the scent-trails of other wolverines, scent-marking a route across an overpass or underpass might encourage wolverines to use the structure more quickly. Of course, acquiring wolverine scent would be tricky, so maybe this isn’t such a brilliant idea. But I’m betting that now that one wolverine has crossed, others will follow with increasing frequency, if there are others in the area.

Speaking of dispersal, High Country News published a thought-provoking piece about the popularity of corridors in conservation discourse, and the very real challenges to actually protecting them. I am a  landscape ecology geek and I love all of the thinking that goes into figuring out sizes of protected areas, island biogeography, and the configuration of dispersal corridors, but….I also worry that in taking an approach that relies heavily on technical problem-solving, we’re ignoring the bigger issue of how we relate to landscape and development. Maybe the focus should not be on setting aside limited areas for wildlife dispersal. Maybe the emphasis should be on setting aside limited areas for development instead, so that we maintain a permeable matrix of natural landscape by which human settlements are surrounded, instead of the other way around. (Yes, yes, I know I’m a raging idealist in addition to being a geek.)

That’s the wolverine news for early February. Looking forward to hearing how you celebrate Wolverine Birthday.

South of 54: The Bioclimatic Constraints of Wolverines on the Edge

(For months, the question floating around the office was, “Has Jeff Copeland’s snow paper been published yet?” It came out in March of 2010. This is a summary of what that paper found. I’ve been working on this for weeks and, like some Sysiphian task, I’ve found that the closer I’ve come to something workable, the busier life becomes, and the further from completion the piece gets. So I’m posting it as is, because I have to leave for Canada tomorrow and then Mongolia the week after that. Forgive any imperfections or lack of cohesion.)

The Magic Line

Find a map of the northern hemisphere, and locate the 54th parallel. Trace its arc across the globe – in Siberia, 54N cuts across the southern tip of Kamchatka and the northern tip of Lake Baikal, then passes just south of Moscow. It brushes past the southern edge of Sweden, decapitates the Danish peninsula, and slices England in half. Across the Atlantic, it comes ashore on Newfoundland, sweeps across northern Quebec, and passes through the top of James Bay. In Ontario, it demarcates the southern edge of Polar Bear Provincial Park, and then cuts across a sweep of sparsely inhabited, lake-studded Manitoba, Saskatchewan, Alberta, and British Columbia, reaching the Pacific at Hecate Strait just south of Alaska. North of 54, the world stretches, colder and ever more severe, in a mix of boreal forest and tundra, towards the Arctic Circle at the 80th parallel. The region is underlain by permafrost, discontinuous but widespread closer to 54N, deeper and more continuous to the north. The landscape, though ridged with several mountain ranges in both hemispheres, is primarily flat, and remains covered in snow until late spring. North of 54, the Pleistocene lingers.

54 North is the wolverine’s Magic Line. In the flat, snowbound tundra to the north of this parallel, everything is, essentially, wolverine habitat, and the species is spread in a continuous distribution across much of the landscape. South of 54, boreal habitat grows sparser, migrating uphill as you go further south, until, by the time you reach the US Rockies, it is pinched into the upper reaches of the highest mountains. Wolverine distribution migrates uphill with the habitat, until a creature designed for cruising the vast and primarily flat North becomes, of necessity, a mountaineer. Restricted to these islands of boreal habitat in a sea of sagebrush desert, the wolverine faces a unique set of challenges that center around access to suitable places to live.

Parameter 1: Persistent Spring Snow

Wolverine biologist Jeff Copeland and his colleagues in the wolverine biology world were attempting to determine the parameters of these challenges when they began to look at variables that might influence wolverine habitat selection. What, exactly, did a wolverine need in order to consider a place livable? Working with telemetry locations and confirmed wolverine den sites from research projects in North America and Scandinavia, they began sorting through a list of possibilities – elevation, aspect, vegetation, prey, weather conditions, proximity to human development. Habitat selection models for wildlife can become complicated as factors interact with each other, but in the case of the wolverine, a single overriding variable seemed to be the best predictor of wolverine distribution: persistent spring snow.

At an intuitive level, this made sense. Wolverines den in the snow, so of course they would tend to adhere  to regions with adequate snow to protect their babies until the kits were capable of limited independence, in early to mid-May. And the logical and intuitive conclusion would be that wolverines, being dependent on snow through May, are vulnerable to reduced spring snowpack predicted in climate models for the next century. All of this would seem to suggest that the wolverine requires protection and careful management to ensure that it remains on the landscape as declining snow levels and rising temperatures limit reproductive habitat. But in science, intuition and logic are never enough. Someone has to prove that the hypothesis is sound, and proof, in science, involves running the gantlet of the peer-review process, and publishing your results.

Jeff Copeland and his colleagues at the Rocky Mountain Research Station took on the task, and proposed an obligate relationship between wolverines and snow. Obligate relationships, in ecology, are relationships of dependence that are restrictive for the organism in question and that in many cases serve to define the environment on which it relies. So an obligate wolverine-snow relationship implies that you will never find a wolverine living in a place without persistent spring snow and, conversely, that if you see a mother wolverine traveling with two kits sometime in late spring, you know you’re in an area where snow persists until at least mid-May.

To test the model, Copeland and fellow researchers used remote-sensing data to construct a map of late spring snow spanning 7 years, from 2000-2006. To qualify as having persistent spring snowpack, a location (represented as a pixel on the map) had to remain snow covered between April 24 and May 15 – the period in which wolverine kits emerge from the den to begin the freewheeling life of a juvenile gulo – without a single day of bare ground.

Norway and Sweden maintain national wolverine den monitoring programs, which allowed Copeland to access precise den locations during the years for which the snow model was constructed. In North America, den location data are more scattered, so the authors of the paper drew on information spanning 1981- 2007 to obtain an adequate sample. In total, they compiled locations of 562 dens (327 of which were in Norway, 160 of which were in Sweden, 10 of which were in Finland, and 65 of which were in North America, which illustrates how little we know about wolverine reproduction in the US and Canada.) To look at year-round habitat use, Copeland compiled winter and summer telemetry locations of instrumented wolverines from 10 studies in North America and Norway. When the den locations were placed on the snow map, 98% of the dens were located on pixels that were classified as having persistent spring snow cover for at least one of the years, and 69% of the time, female wolverines were selecting for sites with snow cover for six or seven out of seven years. In the 2% of cases in which the den locations fell outside the snow map, the sites were investigated and determined to be snow dens; in these cases, the dens were located in expanses of snow too small to register by way of remote-sensing. Here was conclusive, statistically significant evidence that the relationship between wolverines and snow is, indeed, obligate.

The telemetry points reinforced the hypothesis. During summer, 95% of the telemetry locations adhered to the snow map, and in winter, 86% of the telemetry locations stayed within the bounds of persistent spring snowpack. The discrepancy makes sense if wolverines prefer snow; during winter, a greater portion of the landscape is snow covered and wolverines are therefore better able to travel outside the bounds of spring or summer snowpack. (Even then, however, Copeland determined that the wolverines traveling outside the snow map were primarily males – females maintained a higher fidelity to the snow map in all seasons.) Taken together, this meant that no matter how much snow was actually on the ground in a given season, wolverines predominantly operate in places where there is snow in late May.

Predominantly – but not exclusively. In one study, in the Omineca Mountains of British Columbia, wolverines actually appeared to be avoiding the snow locations during most of the year, but occupying those locations during summer when temperatures were highest. This suggested that there was another factor influencing wolverine habitat selection. To expand the test of whether wolverine distribution is limited by climate, Copeland and his co-authors decided to look at the next logical variable: temperature.

Parameter 2: Upper Thermal Limits

Wolverines are designed for the cold and snow, and early investigations into wolverine metabolism focused on the impressive insulating qualities of wolverine fur.  Scientists suggested that a wolverine in a winter coat could tolerate temperatures down to -40º C. But no one had ever tested the upper limits of a wolverine’s thermal tolerance.

For Copeland and his colleagues, there was an easy way to construct a test, without ever handling a wolverine or its pelt. They modeled 50 years of temperature data in the locations where wolverines were hanging out in the telemetry studies, and established that the average maximum August temperature  in these areas was 22° C. They then made a global map of 22°C maximum August temperature and laid it over the snow layer map. The temperature layer painted a cool swath across the boreal north and then, further south, splintered into peninsulas and islands that corresponded to mountains or cool maritime regions. In these insular and peninsular southern regions, the August temperature layer and the snow layer corresponded, but further to the north, where the entire landscape had maximum August temperatures of 22°C,  there were regions with no snow in mid-May. The point of divergence between the snow layer and the August temperature layer was just south of the Omineca study area, at approximately 54N latitude.

The wolverine studies that Copeland included in the analysis crossed 24 degrees of latitude, with average temperature variations of about 10°C between the southernmost and northernmost locations. To the north, where average August temperatures are consistently below 22°C, wolverines operated across the landscape in a more general way. To the south, where average August temperature varies with latitude, they were selecting for locations with lower temperatures – generally, at higher elevations. Year-round, wolverines adhere to swaths or stretches or, further south, scraps and slivers, of boreal habitat.

‘Whales in the Desert’

The paper that Copeland and his colleagues wrote wields the weighty title The bioclimatic envelope of the wolverine (Gulo gulo): do climatic constraints limit its geographic distribution?, and was published in the Canadian Journal of Zoology in March, 2010. The paper answers the question posed in its title with a decided ‘yes.’ In a statistically verified way, wolverines have been shown to select for cold and snow, and to avoid areas that possess neither of these characteristics.

The paper and the science behind it are simple and elegant, and Copeland, in a phone conversation this morning, mentioned that the paper was ‘fun to write,’ because it dealt with three simple factors: areas of known wolverine presence, areas with persistent spring snowpack, and areas with a limited maximum August temperature. The first factor defined the geographic limits of the study, and this, in turn, increases the confidence that the results are valid. Referring to what he and his co-author Kevin McKelvey call a ‘whales in the desert effect,’ Copeland pointed out that in creating a habitat selection model for whales, you will find that whales are avoiding selecting deserts if you include deserts in your analysis. The problem with many habitat selection models is the fact that they are so broad and encompass so much territory that, by default, the ‘deserts’ are included, and you end up showing avoidance of areas or factors that might not actually be relevant to the needs of the species, but that might appear statistically significant in an analysis.

People have speculated about whether wolverines might have been widespread in the past, and were driven up into their current  mountain habitat by expanding human activity.  Copeland says that if he and his co-authors had included all of North America in their analysis, the results would have shown a statistically significant avoidance of human development and lowland areas. Because they confined their analysis to the known current habitat of the wolverine, and were able to show that within that habitat wolverines are making fine-scale selections for specific factors – snow, and low August temperatures – they were able to elucidate something truly significant for the gulo-curious and for managers: wolverines need cold and snow, and they can’t live in places that don’t have it. Post-Pleistocene, wolverines in the Lower 48 have probably always been confined to the mountains.

As Copeland explained the analogy over the phone, the idea of whales in the desert fused neatly with the vision that I hold in my head of the fragmented peninsulas and outlying islands of boreal habitat in the Rockies. I’ve always thought of it in terms of a land mammal having to swim across non-habitat between those islands – exhausting, but possible. But something about the idea of a whale trying to cross dry land seems apt, too. North of 54, the wolverine is swimming in the ocean for which it evolved. South of 54, the wolverine is a whale in puddle in a desert, contemplating survival in a landscape in which it survives by the grace of a cold and snowy climate, but to which it otherwise does not belong.

Federal Review for Gulo Announced

Yesterday the US Fish and Wildlife Service announced that the review for listing the wolverine under the Endangered Species Act has begun. This is the fourth review since 1994; in the first two instances, the wolverine was turned down for protection due primarily to lack of information. The deadline for the third verdict was extended to allow for the publication of a special volume of The Journal of Wildlife Management focusing on the wolverine, which essentially doubled the amount of peer-reviewed scientific literature on the species in the Lower 48. This perpetual shortfall in data has been the wrench in the system for years, and illustrates the challenges of even determining the legal status of a species when information is lacking. (It also illustrates our lack of will to implement the precautionary principle in environmental matters.) In March of 2008, the USFWS returned a verdict of ‘not warranted for protection,’ despite the fact that the articles in JWM strongly suggested that wolverines do face threats. This is purely a statement of opinion and I’m not a conspiracy theorist, but one notes inconsistencies in the 2008 decision between the analysis of data, and the conclusion reached.  The Wolverine Foundation‘s official statement bears repeating here: “…a decision regarding listing protection of the wolverine under the Endangered Species Act, regardless of the finding, should be developed from an objective assessment based on sound science. It is our consensus that this was policy-based, rather than a biologically-based finding…”

Reaching a similar conclusion, environmental advocacy groups challenged the 2008 decision, and the current review is the result of that lawsuit. The only substantial additions to the scientific literature since the 2008 review are wolverine biologist Jeff Copeland’s paper, just published last month in The Canadian Journal of Zoology, linking wolverine distribution to deep spring snowpack, and Mike Schwartz’s November 2009 paper in Ecology, linking wolverine dispersal and gene flow to snowpack, and placing the effective population size of the Rockies (ie, the number of individuals contributing genes to the population) at 35.  Most of the scientific data under analysis will be the same information that was considered in 2008, but these two new papers offer the first statistically conclusive connections among wolverines, snow, and genetic diversity. To put it more simply, these papers link wolverines to the major themes of conservation today: corridors, and climate change. These connections should not be oversimplified, and the ESA review may or may not return a verdict of ‘threatened’ or ‘endangered,’ but these new data are significant to wolverine conservation regardless of the listing decision.

The announcement yesterday also serves as a call for other relevant information that might help the USFWS reach a decision about whether the wolverine should be listed as endangered or threatened under the ESA. The USFWS is looking for well documented scientific data about things like climate change, conservation actions, commercial use, and the distinctness of the Lower 48’s population in comparison to the population in neighboring Canada. Since this is a scientific review process, letters of support (or opposition, for that matter) without accompanying data will not have much effect on the decision itself.

If you do feel like you have information that has a bearing on the conservation status of the wolverine in the Lower 48, the link above will take you to the Federal Register site announcing the review. Comments should be submitted by May 17th. The official date for the announcement of the decision is December 1, 2010.