Wolverine News in the New Year

2015 was a tumultuous year in the world of wolverine research and conservation. At the end of 2014, the proposed rule to list wolverines was abruptly withdrawn, and since then we’ve been waiting to see what will happen with a pending lawsuit and with several new research programs that could provide more insight into the wolverine’s status in the US Rockies. I’ve been pursuing another major writing project, so despite these important developments, I’ve been bad about keeping up with all the news.

2016, however, promises to be a different story, due to a phone call that I received one day back in August. That call was from Jeff Copeland, the renowned wolverine biologist and director of the Wolverine Foundation. He was calling to ask if I would be interested in taking over his position at TWF. I was speechless, which is not a good thing to be while on the phone, but I was overwhelmed with the feeling that you get when someone you admire and respect gives you a huge vote of confidence. When I found my voice again, I said yes. The thought of stepping into this role made my autumn shine, and working with Jeff, his wife Cheryl, and the board during the transition has been a pleasure. I officially began on January 1st. I’ve already shared some of my thoughts about the transition at the Wolverine Foundation website, and I encourage you to check it out. I also encourage you to follow TWF on social media (facebook here; twitter and instagram to follow soon, because yes, wolverines do need to share their photos and 140-character thoughts) to keep up with new research, publications, and policy development headlines. I’ll continue to blog, of course, to provide more in-depth analysis, and to share stories from the field. Yesterday, a judge in Missoula heard arguments for and against throwing out the USFWS decision not to list, and I was fortunate enough to be in the gallery, so I’ll be posting again soon. TWF is sponsoring the Badass Wolverine Challenge, a fitness event for wolverine fans that opens on February 21st, and I’ll also be updating about that shortly. And I’m looking forward to several other projects that I’ll discuss over the coming weeks. For now, though, after six weeks on the job, I’d like to reflect on TWF’s history, and the trajectory of wolverine research and conservation since its inception.

The Wolverine Foundation was founded back in 1996, after a number of the world’s wolverine biologists met in Whitehorse, Canada, and decided that the species needed an organization dedicated to advancing research and science. In the two decades since those biologists collaborated to form TWF, wolverines have gone from being on the extreme periphery of our awareness, to being at the center of research and conservation efforts in the US and beyond. This is not just a spurious claim. A quick search of Google Scholar for articles published prior to 1996 that reference wolverines reveals 1020 hits. Between 1996 and 2015, an additional 5330 articles have been added to the literature.  Admittedly, some of those must be regarded with skepticism — interesting but probably not relevant to the topic at hand are articles such as “A content analysis of family relationships in six comic book series,” the truly mystifying “The grizzly and the wolverine: an alternative to an orchestrated ballet of farm implements,” and the intriguing but probably not scientific “A wolverine is eating my leg.” But even when the search is restricted to articles with “wolverine” in the title, and to remove references to X-Men, postmodern performance pieces, and other non-gulo topics, the trend is the same. Between 1900 and 1990, Google Scholar banks a grand total of 39 articles with “wolverine” in the title, not counting citations, and most of these are species descriptions or mentions in surveys of regional mammals. Between 1990 and 2000, we see 30 articles added to the literature, and between 2000 and 2010, 128 appear. In the past five years, an additional 76 have been published. Of the 273 articles with “wolverine” in the title, 249, or 91%, were published since the founding of the Wolverine Foundation.


Wolverine publication trend, 1900-2010

The number of articles in Google Scholar is a coarse way of assessing the growing importance of a single topic, let alone the impact of a single organization concerned with that topic; there are many possible reasons for the exponential growth in publication. But it’s still indicative. Wolverines are more important to us now than they were twenty years ago, as measured by the time, attention, and resources devoted to them by the global research community. Here in the US, they’ve also become much more prominent in debates about conservation policy as the discussion about listing under the Endangered Species Act and wildlife protection in the age of climate change moves forward, so we can conclude that they’ve become more important to the general public. They are valued more highly, and more widely, than ever before.

During this period of growth in research and interest, the Wolverine Foundation has pushed to develop research and outreach, connect researchers, develop new methods for studying the species, and provide access to the science. In the past twenty years, TWF has supported around 30 projects, either by serving as a fiscal sponsor, or by giving small grants to projects, such as my Mongolia work, which would otherwise have had budget shortfalls. TWF has also played an important role in disseminating information to the broader public by providing scientific input to media, for example in the production of the PBS Nature special Wolverine: Chasing the Phantom, and in numerous popular press and news articles. I can’t claim a direct cause-and-effect link between TWF’s existence and the growth of wolverine research and interest, but the organization has done a great job in bringing wider visibility to good wolverine science. This is how you raise the profile of a neglected species that you consider important. I’m truly excited to be stepping into a role that allows me to continue this work.

The Wolverine Foundation is not an advocacy group, and it will not become one. But saying that a species is important enough to warrant investments of time, research, and the money that accompany both is a vital first step in achieving conservation outcomes. Supporting research into important questions about wolverine ecology is the manifestation of the assertion that a species counts, that it is valued. That research allows the wider world to say, now we know something definite about this animal, and we know what it will take to keep it here in the decades to come. Then the task of creating policy begins, and along with that, the task of making sure that the policy advances the public interest. These last two steps are outside the scope of TWF’s work, but good science remains a critical foundational piece of the conservation process. That is where TWF will continue to position itself in the years to come, and that is how we’ll continue to expand our understanding of wolverine ecology and conservation needs.


New Study on Food Storage and Reproduction

Wolverine kits, at least several weeks old. Borrowed without permission from care2.com. Too cute not to repost.

For years now, we’ve known that wolverines are found in regions of deep spring snowpack and low summer temperatures – Copeland et al’s 2010 paper elucidated this elegant model of wolverine distribution by mapping known wolverine locations from all over the globe and placing these locations onto a map of global snowpack on May 15th, and maximum August temperatures of less than 22 degrees Celsius. The paper showed that wolverines are tied to the cold regions of the northern hemisphere, and linked this dependence on cold to the fact that wolverines give birth in snow dens. The paper was groundbreaking and its publication eagerly anticipated, because it provided enough evidence of climate change threat to support the USFWS’ 2010 decision that wolverines are warranted for listing.

A new paper in the Journal of Mammalogy by Bob Inman, Audrey Magoun, Jens Persson, and Jenny Mattisson expands our understanding of the links between wolverines and the cold, exploring the complex reasons for the evolution of wolverine reproductive timing and behavior.  If the Copeland paper told us that wolverines are indeed climate sensitive due to denning requirements and a cold-adapted physiology, this paper asks why those denning requirements and physiological limits are so strict – in other words, what adaptive advantage does cold-climate specialization offer to the species?

Inman and his co-authors suggest that the wolverine’s strategy is driven by the nutritional needs of the species, and of reproductive females in particular. Pregnancy and nursing are the most nutritionally demanding activities that any wolverine – any mammal, in fact – undertakes, and the successful rearing of young requires a secure source of food. The timing of wolverine births early in the year, according to the paper, allows females to take advantage of a flux of winter-killed ungulates that they have cached, and the nursing and weaning periods encompass the spring surge in baby ungulates and the brief summer explosion of small mammal populations. Persistently cold climates allow wolverines to cache food in an environment where it won’t go bad, allowing them to store sparse nutritional sources and “be efficient in channeling available food resources towards reproduction.” And, suggest the researchers, by living at the outer – or upper, in the case of the Rockies – margins of the ranges of other predators such as wolves and bears, wolverines avoid direct competition with much larger and better equipped rivals. Put all of this together, and wolverines obtain a neat set of advantages by living in a harsh and desolate landscape.

The paper relies on synthesis of existing research, and contains a great section reviewing all the data on reproduction. Wolverines mate in summer, but implantation of the fertilized embryos is delayed until winter. We generally say that wolverines give birth around February 14th (Valentine’s Day) and that the kits are weaned by May 15th (Mother’s Day), because these dates are easy to remember and are, on average, accurate. But in the details of known wolverine birth dates, we see a much wider range, with some wolverines giving birth as early as January, others as late as April. This means that implantation – nidation, in scientific parlance – also occurs over a range of dates, from November through January, with a 45-day gestation. Most of the births do occur mid-February to early March, but the range offers the possibility that female wolverines are responding to environmental factors on a year-by-year basis (several of the females were monitored over several years and had different chronologies in different years.) Does this mean that wolverines might possess some latitude in timing births to correspond to changing snow and nutrition availability over the longer term? Like almost everything else about wolverines, we have no definite answer, but it’s interesting to think about.

The paper also summarizes reports in some studies of very high levels of wolverine pregnancy (implanted embryos). This, too, is interesting, since female wolverines seem to raise very few litters. The data suggest that many females who give birth lose their litters early. Nutritionally, this is more adaptive than struggling to keep a litter alive and then losing it later, since it represents a much smaller investment of resources. Losing a litter early during a year when conditions are sub-optimal gives females a chance to maintain better body condition for next year’s litter, when conditions might be better. All of the attention to this question of reproduction is critical, since we absolutely must understand these dynamics in order to determine effective conservation strategies.

This paper received a fair amount of attention in the press, most of it focusing on food storage: here at the Examiner, at the Huffington Post, at LiveScience, at USA Today (there is, perhaps, a wolverine fan on staff there, because this makes two articles on gulos in two months), at National Geographic, and at MSNBC. I’m sure that there are others out there, too. Most of these articles quote lead author Bob Inman, of the Wildlife Conservation Society, sounding very respectable and scientific – but his secret identity is revealed in an article discussing whether or not the ubiquitous presence of Wolverine the X-Men superhero may also be an adaptation to climate change, in which Wolverine uses his extensive social connections as a food storage strategy: “Understanding why and how Wolverine exists where he does and the various adaptations he has evolved to eke out a living will better inform population management strategies and conservation of the comic industry,” said researcher Robert Inman. I’d heard that Bob was away in Sweden for several months, but now we know the truth.

My own summary of this paper is delayed; I usually like to talk to the scientists to make sure I have all of the implications correct, but the paper came out just as I left for Mongolia, and I haven’t had the chance to talk to anyone. So this is just a basic summary. More later.

Trophic Cascades and Some Thoughts on How Wolverines Affect the Ecosystem

Several weeks ago, a ‘trophic cascades’ buzz surged briefly through the media, with a couple of articles – one in Yale Environment360 – talking about the ‘discovery’ that predators are important to ecosystem function, particularly in regulating biodiversity. This is actually not news to the ecology community – studies of trophic cascades from the 1960’s now rank among classic ecological papers – but perhaps it’s taken longer to reach the mainstream than I’d realized.

I’ve been meaning to write about this because people frequently end up on this blog through queries about the wolverine’s role in the ecosystem. This question comes in several forms – “How does the wolverine affect its ecosystem?” “What would happen to the ecosystem if the wolverine went extinct?” “How does the wolverine help the ecosystem?” Unfortunately for the people who are asking these questions, we still have a lot of research to do before we can provide an answer. But looking at the role of predators within ecosystems gives us a place to begin hypothesizing.

What is a trophic cascade anyway? First of all, you need to be familiar with a basic food chain, which is divided into trophic levels – producers (plants), which take energy from the sun; primary consumers, (herbivores), which take energy from (read: eat) the producers; and secondary consumers (carnivores), which take energy from the primary consumers. Sticking to this very simple structure, it’s easy to imagine that those in the top tier of the food chain – the predators – are having an effect on those in the next tier down – the herbivores. To put this into even simpler terms, otters eat sea urchins, therefore otters have an effect on the sea urchin population.

The idea of a trophic cascade takes things beyond the obvious by suggesting that the otters also have an effect on the plants that the sea urchins are eating. This is less intuitive but likewise pretty simple when you think about it: if there are fewer sea urchins, the plants that they eat are likely to experience some benefit. This, in the simplest form possible, is a trophic cascade: a species affecting other species in non-adjacent trophic levels. These effects have been observed most strongly in aquatic ecosystems, where, for example, the extirpation of sea otters led to the elimination of kelp beds as the sea urchin population exploded. In terrestrial systems, trophic cascades occur at both the small (spiders, grasshoppers, and goldenrod) and large (wolves, elk, aspen) scales.

Of course, things aren’t always this straightforward. There’s no such thing as a simple food chain in nature; energy and nutrients cycle through complex networks of production, consumption, and decomposition, and frequently these webs include tertiary consumers (predators that eat other predators) as well as secondary consumers. And conceivably, the same individual could be both a secondary and a tertiary consumer (a heron, for example, might eat an herbivorous rodent or a carnivorous fish.) Direct numerical effects on population aren’t the only consequence of having carnivores around; research on trophic cascades has provided evidence that there is also an ‘ecology of fear,’ whereby the presence of predators changes the behavior of herbivores in ways that can also contribute to trophic cascades.

To complicate things even further, some secondary consumers – generally referred to as ‘apex predators’ – don’t like other secondary consumers – generally referred to as mesocarnivores or mesopredators – and kill them to eliminate competition, which can have an effect on the preferred prey of the mesopredator. (Wolves don’t like coyotes, and kill them when they can; coyotes prey extensively on pronghorn fawns. Since the wolf reintroduction to Yellowstone, coyote numbers have dropped and pronghorn fawn survival rates have risen. A number of other examples of this phenomenon in reverse – eg, removing apex predators from ecosystems, which is sometimes referred to as ‘mesocarnivore release’ –  can be found here.) If this doesn’t give you enough to mull over in contemplating the complicated relationships among species, consider that there’s also evidence that wolves in Yellowstone, by reducing elk numbers and thereby encouraging the growth of willows and aspens, have allowed the return of certain rare songbirds by providing nesting habitat. As to the effects that those songbirds are undoubtedly having on their food networks, well….you can imagine that the repercussions go on and on.

For a long time, ecologists thought that ecosystem structure was regulated from the bottom up, by resource availability. Only with the advent of work on trophic cascades did people begin to appreciate that top-down regulation and structuring were also occurring. The realization was significant for conservation advocates because it gave a much more quantifiable value to predators, which were traditionally reviled for depleting supplies of game. Traditional Western wildlife management, from its inception, revolved around the removal of predators to ‘benefit’ the ecosystem as a whole. Evidence of top-down ecosystem regulation finally provided some rationale for keeping predators on the landscape (aside from “These animals are cool and inspiring,” which, unfortunately but understandably, has never been enough for some people.)

How does this relate to wolverines? Wolverines straddle the line between being a top predator and being a mesocarnivore; they hunt, they scavenge, they can scare grizzlies or wolves off a kill, but they are also killed by larger predators. Among the high peaks of the Lower 48, where there isn’t much apparent overlap with bears and wolves, they are likely the top predator on bighorn sheep and mountain goats, although they also apparently rely on sheep and goats that fall off cliffs. They consume a wide array of small mammals and may be consuming some plants (chemical compounds derived from vegetation are found in wolverine musk) although obviously not enough to have a major effect on plant communities. The point is, they interact with a number of different species because they are, within their habitat, generalists. One could speculate that a female wolverine denning in an area near pika colonies might have an effect on those pika colonies, which in turn could effect the plants on which the pikas graze. It could also regulate disease transmission among pika colonies by thinning out the population and reducing the density of vectors; conversely, it might have a negative effect on dispersal and the founding of new pika colonies. We could also hypothesize that wolverines might preferentially prey on lambs or kids (the goat variety, not the human….), and that this in turn would restructure the plant communities and maybe the distribution of goat or sheep herds in their high-altitude pastures. Finally – a question that the scientists who work on trophic cascades haven’t, as far as I know, asked – we could begin to test some hypotheses about whether mid-level carnivores or scavengers can affect ecosystems as a whole – for example, if wolverines are preferentially hunting mountain goat kids, do they reduce the mountain goat population enough to exclude some other predator? Do wolverines compete with raptors (by burying carrion, for example) in such a way that the raptors and/or the raptors’ preferred prey is affected? At the northern extent of their range, is wolverine predation on caribou calves high enough to have an impact on the caribou and if so, how does that affect the plants on which caribou graze? Are wolverines on the landscape playing any role in rates of wolf predation by pushing wolves off kills and forcing a pack to hunt more frequently as a result? Honestly, it seems fairly ridiculous to imagine that this might be true – but who knows?

Everything that I’ve written in the paragraph above is entirely speculative, and the alpine tundra ecosystems in which the wolverine lives at the southern edge of its range aren’t necessarily well understood as systems. The point is that we don’t know exactly how wolverines affect ecosystems in either the northern or the southern parts of their range, but it’s likely that they do in some way, and there are a million possibilities to explore. For people who are looking for an answer to how wolverines affect the ecosystem, hopefully the idea of trophic cascades gives you a place to start thinking about the many connections that exist among species and the many possibilities for asking targeted questions on the topic.

How to Help

Last night my sister and I watched the PBS premiere of Wolverine: Chasing the Phantom with a handful of friends who were involved with starting the Glacier National Park Wolverine Project. Seeing wolverines on national television was fantastic, especially with a crowd of people who recognized every mountain and were full of jokes, stories, and the deeper history behind every incident.

The show was the highest-rated of the PBS season, and in the 15 minutes following the end of the show, visits to this blog increased 300% over the previous all-time high. Many were searching for pictures of Jasper and Banff, the captive Alaskan wolverines featured in the documentary. Others expressed interest in learning more about wolverine ecology and biology, and some wanted to volunteer with wolverine research projects. Still others were looking for information on threats, and, alarmingly, a few had googled things like “how to adopt a baby wolverine.” (If it seems slightly Orwellian that I know all of this, all I can say is, writers are all gluttons – pun intended – for knowing who’s interested in our work, and WordPress stats are addictive.) After initial delight over the sudden surge of interest in wolverines, I returned to a much-discussed question among wolverine researchers: how do you channel the enthusiasm generated by a wonderful film into conservation benefits for the species you research, care about, and – yes, I admit it – identify with?

This seems like an opportune moment to address the big question of newly-minted wolverine enthusiasts: what can you do to help?

First of all, keep learning about the species. The more you know, the better for wolverines. The best source of wolverine information remains The Wolverine Foundation, which is run by a coalition of wolverine researchers, including Jeff Copeland and Audrey Magoun, whose projects were featured in the documentary.

Second, do not try to raise a wolverine as a pet. Jasper and Banff are extremely engaging, but they are still, as Steve Kroschel points out in the movie, wild animals.  Wildlife rehabilitation and ambassador animals play an important role in conservation, but wolverines are not pets and most people don’t have what it takes to give one the kind of life it deserves and needs. If you want to adopt a wolverine, consider doing it by making a donation to a research project that monitors wolverines in the wild. Wolverine research projects are able to keep close track of each instrumented animal, and even via GPS collar, the unique personality of individual wolverines shines through. We also do a great job of keeping our donors informed about what “their” wolverines are up to, so it’s a nice way to have all the fun and adventure of having a wolverine in your life, without chewed-up furniture and potential puncture wounds.

Third, the biggest long-term need for wolverine conservation is better data. The wolverine has been petitioned for listing under the Endangered Species Act three times since 1994; the first time, it was denied protection due to lack of data. The second time, in 2008, it was denied protection – arguably – because the evidence of threat was not convincing enough. The third decision is due out in December of 2010; Jeff Copeland’s snow model paper, published earlier this year, may provide compelling enough evidence of threat due to climate change that wolverines will be listed. Or it may not. In any case, if the wolverine is listed, it’s only the first step in figuring out how to protect it, and as the documentary illustrated, finding out anything about these animals is time consuming, expensive, and not for the faint of heart.

After the showing last night, my friends lamented the end of funding for the wolverine project in Glacier National Park. The five year study revolutionized our understanding of wolverine ecology and demographics. There’s a long way left to go, however, and understanding the meta-population dynamics of wolverines at the southern edge of their range could provide important information about how wolverines can survive in a warmer world. Wolverine research is critical to wolverine conservation. I don’t usually do this directly, but I’m going to do it now: if you are inspired by the film, by wolverines, by the researchers who push forward through every hardship to learn about these animals, then give directly to a research project. A quick breakdown of costs: $25 buys supplies for non-invasive DNA sampling. $60 analyzes a DNA sample. $150 buys immobilization drugs. $250 covers a flight to determine whether a female is denning. $3000 buys a GPS collar. Any amount – whether it’s $5 or $5000 – shows an interest in and commitment to the species, and we appreciate it.

I work for the Northern Rockies Conservation Cooperative, which maintains the Absaroka-Beartooth study, and if you donate to us, I’ll be thrilled (and if you want, I will personally send you updates about what the project wolverines are up to.) But there are several fantastic projects out there; you can find summaries of global research projects on the Wolverine Foundation site, to learn more about which one you want to contribute to. The Wolverine Foundation, as the organizing research body, is also in need of support.

Fourth, help out by becoming a citizen scientist if you live in wolverine territory. If you’re a backcountry skier, a snowmobiler, a hunter, a backpacker, a climber, or anyone else who spends time in the high country, let us know if you see a wolverine or tracks. You can find a pocket-sized card to download and take on your next trip here.

Finally, don’t panic. So many of our narratives about species conservation have been built around a sense of urgent threat that we default to that story whenever we are trying to figure out how to do something good for a newly-fascinating species.  I’ll write more about this over the next couple of weeks,  but the short story is this: there’s no single activity that’s directly threatening the survival of wolverines as a species, and there’s no single action – aside from reversing global warming – that will help them. Instead, it’s going to take innovation and creativity to create a new conservation model that will work for wolverines and for montane ecosystems as a whole.

Thanks to everyone who watched last night, and for those who missed it, you can see the entire documentary online at the PBS website. To writer/producer Gianna Savoie and her crew, many congratulations on a great film, and to Nature, thanks for continuing to fund and broadcast high quality work.

Film festivals, baby wolverines, and an impending glacierless century?

For the past two weeks I’ve been meaning to write about a conversation that I had with Gianna Savoie about her documentary Wolverine: Chasing the Phantom, review Doug Chadwick’s book The Wolverine Way, and post a synopsis of Jeff Copeland’s snow model paper. But last week I learned that I’d received a substantial grant to return to Mongolia to look for wolverines there (!) as part of a longer term, large scale study of wildlife and climate change, followed quickly by a series of conversations about a possible PhD associated with the upcoming Mongolia research. Added to a carnivore conservation meeting that NRCC will be facilitating in Montana, and an absolutely necessary diversion choreographing and filming a Bollywood-esque dance number in support of river conservation with a bunch of friends over the weekend, my head has been spinning (literally, during the dance; figuratively for the rest of the time.)

The Wildlife Film Festival is underway in Missoula, Montana this week, and Gianna’s film is showing tomorrow, Thursday the 13th, at 12:30, and on Saturday the 15th at 5:30. The film won a ‘Made in Montana’ award and was also recognized for outstanding scientific content. And it also features some of the only footage you will ever see of live wolverines. The schedule is available at the film festival’s website. PBS will air the documentary in November, so if you can’t make it to Missoula this week, keep your eyes open for the film this fall.

The Missoulian published an article today about Glacier National Park’s centenary. 100 years after its founding, Glacier’s namesake features are nearly gone. Glacier hosts what is probably the most robust wolverine population in the Lower 48, and the ecological shifts that are occurring there as a result of climate change could have serious effects on wolverines throughout the Rockies, not to mention a host of other high-altitude species.

Finally, in my few opportunities to check on the blog over the past week, I’ve noticed that a number of people have arrived here in search of information about and pictures of baby wolverines. In fact, over the existence of this blog, ‘baby wolverines’ and searches for information about reproduction are some of the most common terms leading people here. So if any of you arrive here looking for information about wolverine kits, I think it’s great, and I’m curious – is a class somewhere doing a project on wolverine ecology? Or are people just generally interested in baby wolverines? I would love to know, so leave a comment if you happen to be so inclined. For the best information on all aspects of wolverine life history and ecology, organized in a way that is much more accessible than a blog, please visit The Wolverine Foundation’s page on life history. There are links there to information about denning and reproduction that you will find interesting. Unfortunately there aren’t so many great pictures of baby wolverines out there, but I promise to do my best to take some if I ever stumble across a den.

Den Search

A few weeks ago, Jerry Longobardi,  Wyoming Game and Fish game warden for Teton County, came across a hole in the snow on the west side of the Tetons, with wolverine tracks leading into and out of it. Photos of the site circulated among WY Game and Fish, WCS, and NRCC, and the verdict was clear: they were wolverine tracks. The critical question was, was the hole a den, or did it simply represent a food stash, or a curious wolverine digging in the snow for a rodent?

The hole, with wolverine tracks

WCS ran a research operation in the Tetons for many years and documented what to date remains the only confirmed instance of wolverine reproduction in Wyoming, also on the west side of the Tetons. WCS is still the primary research organization for the Tetons even though they are not currently operating traps here. But because their operation is based in Montana, coming down to Jackson to investigate the site would have been a haul. I volunteered to ski in with Jerry a few weeks after the original sighting, to see if the area was still being used and, if it was, to try to collect DNA samples by picking up some scat. We set out on Friday. It had been snowing heavily for the past six days, pure wolverine weather, and as we headed west, the prospect of finding a den buoyed my spirits more than the first glimpse of sunshine in a week.

The chances of stumbling across a wolverine den by accident are minute, and den detection remains one of the elusive objectives of most wolverine research projects. An instrumented female will provide a location by localizing – staying in one spot for a number of days – which wolverines seldom do unless they are denning. But detecting dens this way requires a trapping operation before the denning period, reliable capture and instrumentation of female wolverines in the region, and the money and skilled pilots to fly repeat telemetry flights in rugged mountainous terrain three times a day over the course of four days at the beginning of the denning period. If all of these circumstances come together and the instrumented female is picked up in the same location over the course of the four days, then you know you have a den. This method is time consuming and expensive, due to the front-end investment in trapping in remote locations, and the costs of telemetry flights. For years research operations have tried to develop flight-based surveys for dens, but despite the Absaroka-Beartooth Project’s success in developing a flight-based systematic survey for presence-absence of wolverines in a given region, no one has been able to reliably locate dens of uninstrumented females from the air. So finding a den by any means other than telemetry is rare.

The site, as pointed out on the map, was not in what I would have considered denning habitat – generally, one thinks of a mother wolverine choosing to situate herself in a high cirque, and the forested ridge where Jerry had come across the hole didn’t seem quite right. But then again, what do we really know about wolverine denning habits in the Tetons, with only one den ever discovered? Besides, I wanted it to be a den, so I suspended judgement and remained optimistic.

We took a snowmobile for the first few miles and then skied in from there, not wanting to disturb the wolverine, if she was there. GPS coordinates led to a swath of snow on a steep hillside,  where despite high hopes, there was no further sign of disturbance. We removed our skis and slid down the slope to investigate for tracks, but there was nothing. My heart sank almost as deeply as I did – the snow was thigh deep and I plunged through the bottom of the snowpack and snagged my foot in a tangle of branches. In the struggle to extricate myself, I ended up upside-down, head pointed downhill. It might have been a dangerous situation if I’d been alone, but it also illustrated that this could indeed be denning habitat. Wolverines seem to favor slopes underlain by either sizable talus, or downfall. It seems that they dig into the snow for access, and use the cavities formed by the boulders or trees to provide structure to their dens. The hollow that I’d fallen through, and the branch that had snagged my foot, would be perfect for a wolverine. And the depth of snow, along with the cover provided by the forest, suggested that the snowpack would probably be adequate to provide necessary cover through mid-May, when wolverine kits are finally independent enough to travel on their own.

We dug into the den site until we hit ground, but found nothing – no sign of bones or of anything else a wolverine might have been eating. Jerry had found a second hole several hundred yards uphill from the first, so we skied up to investigate that as well. Again, there was no sign, and because the snow was terrible, we called off further searching and headed back.

Later, Jason said that the lack of tracks didn’t necessarily mean that it hadn’t been a den. Female wolverines generally occupy a series of dens in the course of raising their kits – a natal den, in which the kits are born, and successive maternal dens, in which the kits are nursed, raised, and eventually weaned. Jason estimated that a mother wolverine moves about 300 yards between den sites – which was approximately the distance between the first hole that Jerry found, and the second.

Even if it wasn’t a den, Jason suggested that it would be a good idea to go back and dig more extensively to see if we could uncover some sign of what the wolverine might have been doing in the hole. Food habits data, while not quite as thrilling as the prospect of finding a den, are also rare and valuable.

We’ll give it a few weeks, and then I’ll head back up to check out the site again.