First Captive Kits in the UK

Three captive kits born in January have emerged from their den and are now on public view in the Cotswold Wildlife Park in Oxfordshire, England. BBC has posted a video of the kits, which are the first ever born in captivity in the UK. The Oxford Times also ran a story about the event. The kits and their parents are part of a European captive breeding program for endangered species, and the kits will eventually move to new homes as part of this program.

The kits were in the den for nine weeks, which is slightly less time than we generally allow wild wolverines, although there is some debate on this. Right now we use February 14th as the default birthday for wild wolverine kits, although this probably ranges from January through March, depending on the female and local conditions. We use May 15th as the benchmark date at which kits are out of the den – and, by extension, the last date at which snow must remain on the ground in order for a region to support a breeding wolverine population. These dates allow a full 12 weeks in the den. Some wolverine researchers believe that the May 15th date might be later than necessary, however, and propose a late-April cutoff for den emergence and snowmelt.

The BBC piece mentions that the female has kept her mate away from the den and the kits. Traditional lore and early research in Scandinavia suggested that males entered dens to kill kits, although later research suggested that infanticide was probably the result of interloping males killing unrelated babies. The Glacier National Park project showed that fathers visited their kits and might even help raise and teach them, and in the Absarokas, our male M57 was observed in close proximity to F3′s den last year. We now know that F3 had at least one baby in 2011, a male, so this may be further evidence that M57 played some role in raising the family. On the other hand, the dynamics of wolverine social interactions remain murky, and there may be more to the story than we are aware.

In any case, the birth of these three captive kits is a big event for the UK – perhaps even the first wolverine births there since the Pleistocene. If you’re lucky enough to be in the area, drop by the zoo and say hello to them, and be sure to take some pictures and share them here.

 

 

Where Wolverines Are Born

When I set out last week with the coordinates for F3′s den programmed into my GPS and the site marked on a series of paper maps, I couldn’t shake a feeling that approached sheer giddiness. The opportunity to examine a wolverine den site is akin to winning some kind of wildlife biology lottery; the dens are as inherently rare as the species, and the dens that are known to science are even fewer. Only around 15 have been documented in the Lower 48, leaving a huge gap in our knowledge of reproductive dynamics. For years, F3 had failed to den, and the instruments on our other female, F133, had died, so we had no way of knowing whether she had had kits. When F3 evidently did den this year, I was ecstatic, but I was also in Cambodia. I was starting to think that I would never have a chance to investigate a den site. When I made it back to the Rockies earlier than expected, in August, getting to F3′s den site was one of my priorities.

A crew visited the den in May, when the snow was still on the ground, and some of the same crew members had gone back once the snow melted, in July, to investigate the site and to see if they could find scat samples. The spring crew hadn’t seen the kits or verified their existence, so however strong the circumstantial evidence, we couldn’t be certain that the site was a den instead of a food cache, and we couldn’t say with confidence that F3 and M57 had reproduced. The July crew had looked for latrine sites, which are proof that a site was used as a den. And the crew found them in abundance, pulling out a number of scat samples for analysis. They hadn’t gone digging for the kits or attempted to instrument the babies in May because of funding constraints, so the scat samples, in addition to confirming that this was a den site, also offered a chance to identify new individuals and perhaps determine their sex.

The important work had already been done, and my own trip was half fun and half pilgrimage. I wanted to visit the place where F3 had – presumably – brought her first kits into the world, and I wanted, after nearly a year away, to be back in mountains that form some part of the mental and emotional landscape of home.

The route into that landscape followed a trail for a while, and then cut away from the trail and up gentle south facing slopes, warm with late summer sun and the scent of dust and pine. At the crest of a pass, the world dropped away, the slope plunging steep and precarious into a narrow pine-cloaked valley that swept back to intersect with the endless marching peaks of the high Absarokas. These north-facing slopes were utterly different from the warm hills I’d just left; I had to edge my way down, dancing between tree trunks for support, the force of gravity and the angle of the pitch propelling me towards freefall. The trees were thick, the shade dense, the temperature so much cooler that I paused to put on my jacket and hat.

Possible wolverine scat under a log, about 0.4 miles from the den site.

As I crouched to pull out my hat, I noticed a huge pile of scat under a log near my feet. I was still a half mile from the den site, but the scat was definitely carnivore and seemed mustelid. It was a bit small, but they were kits, after all. I hadn’t been expecting to collect samples but I did have two ziploc bags on hand, so I shoveled the scat and a large chunk of fur into the bags, GPSed the location, and continued to slide downhill through the dense, cold forest and small open meadows. These meadows were saturated – with streams, with flowers, with warmer patches of sunlight, and with the same breathless silence that hung over the trees. The quiet was ancient and deep and almost tangible, so that I felt like I was diving down and further down through a substance like water, into some other world.

Among all the trees, I wasn’t sure how I would ever find the actual den site, but as I crossed another meadow and stopped to look across the stream that drained it, a patch of pink fluttered from over the water. In May, the crew had tied flagging tape to the tree branches directly above the six entrances to the den. Now, in August, with the snow melted, the tape hung fifteen feet overhead. Beneath the tape, F3′s excavated snow tunnels had led down to cavities sheltered by fallen trees. I’d found the tape, and I’d found the den.

A wolverine's-eye view of part of the den site. The chambers were beneath the downed trees. Note human for scale, and pink tape in tree overhead. This marks the approximate depth of the snow in May.

The crew had already collected all the samples, and I spent a long time simply exploring the area and then sitting and basking in the vast silence. The multiple den entrances had sprawled across an area of approximately 120 m²; the tunnels were probably connected beneath the surface. Beneath the largest of the downed trees on the ground, a hollow against the root ball seemed to have served as one chamber, with two others located among the branches further up the trunk. Against another downed tree, another flattened area between branches suggested a chamber as well.

One of the hollows that was part of F3's den site.

I tried to imagine the family down under the snow in a world of compressed ice, first as newborns and later as more active babies. Did F3 dig new tunnels as the kits grew, or had she constructed the whole network at once? Did she move them from place to place as waste accumulated? At what point did the babies begin to move around through the tunnels on their own? Or did they simply wait, curled up around each other for warmth, where F3 left them when she went out to forage? Had M57 come down here as well? The crew in May had heard his signal and found his tracks crossing their own ski trail; he had traveled directly to the den from the distant location where the crew had heard his signal earlier in the day. If he had gone into the den, what did he do while he was down there? Did he bring them food? Keep an eye on things while F3 was out? (She hadn’t been in the den the day the crew visited.) Play with the kits, add his warmth to theirs, wrestle with them to toughen them up for the outside world? When had they left this place, and did they ever return?

I looked up from the logs, scanned the trees, but everything remained still – no sign of wolverines, or of anything else. The most important ecological question – why here? – remained unanswered, but my personal reasons for being there had been more than fulfilled. I was overwhelmed again by the extraordinary stillness of the place. Later, it came to me that the meadow was suffused with a sense of peace that goes far beyond our normal conceptions of that word – the peace of the Wild, a peace that is so powerful because of its utter indifference to human concerns or moral order, a peace that is edged with on-going loss and ferocity and struggle that are, nevertheless, somehow more acceptable and less alien in places like this. It was, I hoped, a good place to be born a wolverine, and I was profoundly grateful to have seen it.

Gulo Dads

Back in the days when the world believed nothing but ill of wolverines – that they were nasty, smelly, anti-social animals intent on wreaking havoc on various human enterprises – male gulos had a reputation as infanticidal villains who would kill their own kits in the den. Scandinavians reported instances of male wolverines entering dens in their territories and killing the babies, which made no sense from an evolutionary perspective, but which fit the wider perception of the species.

Not until the Glacier National Park project did that perception begin to change. Jeff Copeland, Rick Yates, and the project volunteers observed male wolverines visiting dens – but apparently just to socialize with their families (author Doug Chadwick speculates that they might also bring their mates food, but this hasn’t been observed.) Males in the Glacier study also traveled with their juvenile kits of both sexes, showing them how to survive in a harsh landscape before the kits dispersed. This was gratifying to wolverine lovers, and it also made a lot more sense to those who believe in a rational universe. Why put all of the effort into reproducing if you’re just going to kill your own offspring? A caring gulo dad made much more sense than a homicidal one. Observations of kit-killing in Scandinavia may have involved males taking over territories of other males that had died; the destruction of young by interloping males is fairly common among mammals, and would make sense for gulos in Scandinavia, where hunting levels have traditionally been high and wolverine turnover through a given territory would also have been high. Towards their own kits, however, wolverines appear to be attentive fathers.

The wolverine’s change in status from bad dad to good was welcome, and the new narrative has caught on quickly. It was highlighted in the PBS documentary and in Doug Chadwick’s book, and now the wolverine has made Scientific American’s list of the top eight fathers in the animal kingdom. I’m pleased, but I can’t help but reflect on the fact that this new animal superdad comes at a convenient time in American history. He and the mate share duties and spend some quality time together (M57 and F3 seemed to be traveling together frequently during 2009 and 2010; she came to visit him when he was in one of the live traps), but most of the time they’re busy independently roaming around and making a living. He’s not an overbearing patriarch, he’s a cool guy who hangs out, takes the kids out on adventures when mom is busy, and maintains a meaningful relationship with his offspring during their adolescence.  I’m not sure that Americans of a century ago could have appreciated this particular picture of the nuclear family as a constellation of individuals maintaining their independence while also retaining family ties. But to those of us who wish our dads a happy father’s day via google phone from Mongolia, for example, or spend months away from our male companions in order to pursue our work or our research, or insist on equal childrearing duties – or who simply want our mates to be incredibly badass and rad – the picture of wolverine family life seems suspiciously familiar.

So this comes a little bit late, but Happy Father’s Day to all of the gulo fathers out there, and thanks for the inspiration. The wolverine life cycle is marked by American holidays; kits are born around Valentine’s Day and weaned around Mother’s Day, which is neatly symbolic. We can’t say this for sure, but we can imagine that by Father’s Day, wolverines are beginning a summer of hanging out with dad – that as I write, M57 and his kits are cruising the snowfields at the cool, shaded bases of cliffs somewhere in the Absarokas, that the kits are chasing each other and wrestling until M57 stops suddenly, catching the scent of something beneath the snow. That the kits are attentive now as he starts to dig, unearthing the carcass of a goat that slipped from the cliff back in February. That they will remember the strategy of following cliff bands, the scent of meat eight feet below the surface, and the particular way that he digs it out, and that these things that their dad teaches them will help them survive in a rough world.

The Den

Last week, a small crew on skis set out into the high mountains of the Montana wilderness. They were headed into wolverine country, their objective a series of scattered points close to treeline. The points had been obtained during telemetry flights in April, and they indicated that F3, a five year old female wolverine, was restricting her movements to a small portion of her usual range. Under normal conditions, F3 might be found anywhere within an approximate 300 km² sweep of rugged country. Over the past several weeks, however, she had limited herself to a few drainages in close proximity to each other. Her behavior unleashed a wave of excitement among the wolverine crew who had been tracking her since 2007; restricted movement is the classic indication that a female wolverine is in a den with kits.

Determining F3′s reproductive status has become an annual springtime ritual at the Absaroka-Beartooth project, fraught with trepidation, surges of hope, and, inevitably, disappointed resignation to the fact that, once again, the project’s sole instrumented female wolverine has failed to produce kits. We’ve been engaging in this ritual since F3 was first captured in 2007. For the first two years, she was young, and, as far as we knew, there was no male in her territory, so the absence of a den in 2008 and 2009 wasn’t such a surprise.

F3 in 2008, captured by an automatic camera at one of the project's live traps.

Then, in spring of 2009, the Wildlife Conservation Society’s wolverine project took charge of a young male that had been accidentally caught in a bobcat trap in Idaho. WCS released the wolverine, M57, in Montana, and he promptly headed for F3′s territory. We knew that F3 and this male – notable for his white paws and his unprecedentedly relaxed attitude when captured by the project’s live traps – were traveling together throughout 2009, and the tension over F3′s status in spring of 2010 was palpable. For the first time, we had real grounds to hope for babies.

The question was especially urgent for the project because the work done so far had provided no evidence of reproduction in Yellowstone or the ranges immediately to the north, south, and east. In fact, those ranges seemed strangely vacant; the habitat appeared good, but the wolverine population was sparse even for a rare carnivore. Over the course of five years, the project had documented two immigrants to the study area – M57 and a female, F133, who was born in the Gallatins and who traveled across Yellowstone to take up residence south of the park. But there had been no births. This suggests that, at least in Yellowstone and its immediate surroundings, the wolverine population currently depends on dispersing wolverines from further to the north and west. With only a single den documented in Wyoming – in the Tetons – the data also suggest that Wyoming’s population might rely on input from populations in Montana. And with talk of reintroduction following M56′s trip from Wyoming to Colorado, the need for a healthy region-wide meta-population, with as many interconnected nodes of reproducing wolverines as possible, became even more urgent. Any further understanding of reproductive dynamics and denning characteristics – not to mention the sheer and simple fact of more wolverines on the landscape – would be invaluable.

In 2010, a series of telemetry flights eventually indicated that F3 wasn’t denning. We caught her in March of 2010 and were finally able to determine that she was not nursing, although she and M57 were still traveling together. Disappointed, we held out hopes for 2011, but by now the project was officially over and finding resources to keep it going was becoming more and more challenging.

This season, F3 went into the trap early, in January, and the crew noted that her teats were enlarged –  a real reason for hope. The weather remained ferocious throughout the spring, making flights difficult, but when a series of telemetry points finally came in after flights in April, F3′s apparent localization added further evidence to the argument for kits. Finding proof, however, was necessary, and the mission was urgent: wolverine kits leave the den in early May, and the dens themselves, dug in the snow, are ephemeral and nearly impossible to identify once the snow is gone. From the time the points came in, the crew had approximately two weeks to get to the area and figure out what was going on.

The trip in took three hours of skiing, over a steep pass and through heavy snow. At the outset Jason Wilmot, who was leading the trip, listened for F3 and M57 and picked up M57′s signal to the south. There was no indication that F3 was anywhere nearby, and the first point that the crew reached yielded nothing. Jason and the crew pressed on to the next point.

Here, at the pass, they picked up tracks, and then more tracks, and then an explosion of tracks. This, too, was strong indication of a den, and sure enough, backtracking the prints, they found a hole. And then another one. And another. Altogether, the crew discovered six holes in the snow, some apparently linked beneath the surface. The tracks were melted out and the crew were unable to determine whether they came from multiple animals, let alone animals of different sizes. But the evidence for a den and kits was strong.

The crew had already made the decision not to instrument the kits – without the funds for flights to monitor them, it would have placed unnecessary stress on the animals – so they didn’t dig to see if the babies were underground. Instead, they collected DNA samples from the tracks and the entrances to the holes. They listened for F3, but she was still absent. If there were indeed kits, the family might have already left the den permanently, but F3 might just as easily have been out on a foraging run, and the kits could have been curled up in a chamber in the snow beneath the crew’s feet, pondering the strange vibrations of skis and human voices.

Before they left the site, Jason listened again for M57. The signal came in, and it was loud – M57 was somewhere nearby. Employing a trick that wildlife biologists use to determine exactly how close an instrumented animal is, Jason removed the antenna from the receiver and held out the cord with its metal end. If an animal’s signal still comes in without the antenna, the animal is really close. M57′s signal continued to boom in. He was right on top of the crew, probably watching them from somewhere in the trees. As Jason and the remainder of the crew skied out, they crossed M57′s tracks coming into the basin; the wolverine tracks were overlaid on the ski tracks of crew members who had already skied out. From his position far to the south earlier in the day, M57 had traveled directly to the den site. This was further circumstantial evidence that this was indeed a reproductive den, and that M57 was coming to check in on his mate and offspring – a pattern detected on numerous occasions by the Glacier Park and WCS projects.

Without having seen the kits, we can’t confirm that F3 and M57 reproduced. But the evidence is good. From here, we’ll use genetic analysis to try to determine if there are kits and if so, how many. We’ll return to the den site in the summer to gather more DNA samples. If there are kits and if they survive the summer, they are likely to remain within their parents’ territories for the next year, and F3 and M57 are likely to show them all the good foraging spots – including the project’s live traps. We may have the opportunity to capture and examine the kits this winter, to at least determine sex. If we find the funds, we may be able to instrument them and monitor them as they approach dispersal age. This could provide crucial information about connectivity among the different populations, and the extent to which southern populations really are dependent on dispersers from Montana. Overall, it’s exciting and hopeful news for the project and for wolverines at the edge of their range.

Break out the Champagne! (Tentatively….)

The sky finally cleared enough last week to get two flights into the air, on Wednesday and Saturday, and F3 was in the same location for both flights!

We’ve tentatively concluded that she is indeed localized and that this, along with evidence of pregnancy when she was caught in January, suggests that she has kits. The pilots observed a large number of tracks in the vicinity of the signal as well. With wolverines, assumptions can get you in trouble, so I’m trying not to invest too much in the idea of these kits until someone has actually seen them. But the evidence points to a new family of wolverines in the Rockies.

A field crew will ski in to investigate and perhaps set up a camera at the site. We probably won’t instrument the kits; the project is currently at a low budgetary ebb and we lack the funds to regularly fly and monitor kits, which would be necessary to gather the data that telemetry could provide. This is unfortunate, since dispersal is one of those critical parameters for understanding population dynamics, especially in this tiny population node at the very edge of wolverine range. A site visit and a camera will allow us to determine how many kits F3 has, and perhaps their sex, and may even offer some information on whether M57 is visiting the den, and how often.

I am simultaneously thrilled – we’ve been waiting years for F3 to have babies – and a little disappointed – I am currently out of the country and won’t be able to participate in the den visit. But the disappointment is all selfish, and the excitement is absolutely overwhelming.

Further exciting gulo news came out of Oregon today – after researcher Audrey Magoun tracked a wolverine in the Wallowa Mountains of eastern Oregon last week, her camera traps captured images of two individuals in the same area. Audrey and her husband have reset the camera stations to photograph the animals in a way that will allow them to determine the sex of the two animals.

After years of sighting reports from Utah, WCS did surveys last year and picked up tracks in the Uintas; the tracks looked like wolverine tracks, but they couldn’t confirm the ID. This winter, a Forest Service biologist found and documented a set of tracks in the Uintas as well, and the photographs suggest that Utah does have at least one wolverine after all. Where did this wolverine come from? This is one of the reasons we need the capacity to monitor kits.

Further to the north, in Canmore, British Columbia, researcher Tony Clevenger is gathering DNA samples by way of hair snares to study Canada’s wolverine population. Canada’s wolverine population is more robust than the population in the US Rockies, but Clevenger and his colleagues are trying to estimate population numbers and determine whether the animals are being affected by infrastructure development.

All around, it’s been a great week in the gulo world. Now I’m looking forward to hearing about the kit expedition, and having final confirmation that F3 and M57 have babies.  (By the way, do people really celebrate the birth of a human baby with champagne? Or is it cigars? Or something else? I can’t remember. In any case, I am proposing that the birth of wolverine kits be celebrated with champagne henceforth….)

Waiting

In an earlier post, I mentioned that March is the Month of Truth for all those researchers eagerly awaiting confirmation that their wolverines have become parents. In a post that preceded that one, I also mentioned that there are a million things that can prevent you from being able to figure this out. Make that a million and one. The easiest way to determine whether an instrumented female has kits is to fly three days in a row to see if she’s localized. Wolverines, notorious for their constant restlessness, don’t generally stay in one place unless they have something to keep them there, and that usually means either a gigantic carcass, or kits. So if the female is located three days in a row in the same place, she’s probably in a den.

The procedure is pretty straightforward, unless you live in the Rockies in a year when winter descended with fury in November and seems disinclined to leave, at all, ever. For all of March, and for the first two weeks of April, we’ve waited to a clear window to fly for three days. Patience may be a virtue, but in this case it hasn’t been rewarded. We’re still waiting.

If F3 does have kits, they are now two months old. Their fur is darker and longer and coarser, they are bigger and more active, their feet are beginning to take on the profile of gigantic snowshoes. Their tails are developing from fuzzballs into shaggy brooms, and they are undoubtedly becoming more restless to be outside. F3 may have moved them to a maternal den further upslope, a place where the snow is deeper and more secure than the natal den where they were born. The kits have about one month left in the den, and then they and F3 will head into their first summer roaming Montana’s high peaks; she and M57 will help them figure out how to find food, how to avoid predators, and how to make a living in a harsh environment. They will stay in their parents’ territories for about a year before striking out to find their own stretch of wilderness.

Hopefully we can determine at some point over the next week whether she is actually denning. Whether she is or not, female wolverines and their kits in the Montana, Idaho, and Wyoming Rockies, in the Cascades,  and, indeed, all over the world, are preparing to leave the den and head out into the wider world within the next few weeks – exciting and perilous times for the next generation of gulos.

Week Four in the Life of a Kit

A German engraving of a mother "veelvraat" and her kits.

Somewhere among Montana’s high peaks, a female wolverine is curled around her two kits. The babies have more than doubled in size since they emerged into the world about a month ago, pure white and barely big enough to fill a human palm. Their fur has darkened now to a pale gosling gray across their bodies, and to a rich chocolate brown around their eyes and noses. Their ears are still flat to their heads in the way of small animals, and their tails are fuzzballs. Their feet still seem tiny, no hint of the gigantic snowshoes which will eventually carry them across thousands of miles of rock and snow and ice.

These pale, fluffy infants have spent most of their first four weeks nursing and sharing warmth with each other and their mom. When she leaves to hunt or scavenge, they are insulated by the snow overhead. The den that they occupy is buried beneath at least ten feet of snow – probably more – amid the tangled branches of downfall or a warren of talus, and accessed by a series of narrow tunnels that the female wolverine has excavated. They are safe from any but the most persistent, reckless predator. Their mother is gone for only hours at a time, and she returns with a stash of snacking material – the femur of an elk killed during hunting season, a chunk of meat from the carcass of a mountain goat that slipped from a cliff, a duck that, lost in a storm too far north during migration, froze to death and was buried in the snow. Occasionally, the kits’ father visits the den, perhaps marking the entrance to let any other wolverines know that the babies inside are defended, and maybe even venturing down into the tunnels to visit his mate and babies.

Hopefully, this is a portrait of F3′s and M57′s family life right now.

March is a big month for wolverine researchers who think that one of their female gulos might have gone maternal. This is when we begin the tough work of trying to figure out whether the wolverine in question has actually denned and produced kits. Despite many efforts to develop a non-invasive method for answering this vital question, the most reliable way to figure it out remains instrumenting the animal earlier in the year and then flying replicate flights within the first month of the denning period – which begins in mid-February – to see if she’s localized. Few things keep a wolverine in one place, so if a female is “observed” via telemetry in the same location over three consecutive days in March, she’s probably in a den.

F3 should be among these new mothers, but some additional information has complicated the usual uncertainty. When F3 was captured in late January of this year, her teats were noticeably enlarged. We figured that this meant that she was pregnant, and that teat enlargement begins at nidation, the point at which the fertilized eggs implant in the uterine wall and begin to develop. Some folks with wolverine experience have suggested, however, that teat enlargement doesn’t begin until the female gives birth. F3′s teats this January were not large enough to suggest that she was actually nursing at the time of the capture, but large enough to suggest that something reproductive was happening – or had, within the past year. Yet when we collared her in late March of last year, her teats were so flat that they were nearly non-existent (Apologies, F3, but I’m assuming that given the badass gulo attitude, wolverines don’t have a sense of modesty about such personal attributes….)

This means one of two things: that teat enlargement does begin at nidation and that F3 had babies this year; or that teat enlargement only happens once a wolverine gives birth, and that F3 had kits last year – sometime in April or later. The latter scenario would be utterly unheard of, far later than a wild wolverine has been recorded giving birth before. I did a quick search through the literature, and couldn’t find anything conclusive about  the physiology of wolverine nursing, so I don’t have any definite information on which to base an answer.

I would be shocked if she had had kits last year, but there is one other complicating piece of information. On the day that trapping season closed showing no wolverines taken in Region 3, a trapper called in to report that he had killed a small female wolverine in the the Absarokas. For a while, we were convinced that this was F3, because the wolverine was taken out of an area close to F3′s territory, but the dead animal was apparently very young, and we eventually confirmed via telemetry that F3 is still alive. Given the exclusivity of wolverine territories, F3′s tolerance for another female within her kingdom would be strange – unless it was her yearling daughter. And then it would make perfect sense.

F3 dropped last year’s collar a few weeks after we put it on her in March of 2010. This collar would have encompassed the critical time when she might have been raising these phantom kits. We retrieved the collar in late summer of 2010, brought it back to the office, and plugged it into the computer. The collar had malfunctioned; it contained no data. F3, who, as I’ve said before, somewhat embodies the trickster-ish nature of her species, managed to keep us at bay once again.

This mystery should be resolved with flights over the next few weeks, hopefully showing that F3 is indeed up there in a den, nursing kits and preparing them for a wild life in the mountains. But really, keeping track of F3 wouldn’t be worth it if she didn’t keep us guessing.

Happy Wolverines’ Birthday

I wanted to quickly post two thoughts: first, belatedly, Happy Valentine’s Day. This is actually an important day for wolverines all over the world, since it marks the approximate date of birth for every wild wolverine on the planet. As I write, female wolverines from the US to Canada to Russia to Mongolia to Scandinavia are burrowing into their snow dens and giving birth. If our female wolverine F3 is pregnant this year, that’s what she is most likely doing too.

At some point soon we will try to determine whether or not she’s localized by sending a telemetry flight on three successive days.  If the flight locates her in the same area over those three days, she is most likely in a den with kits. I’m also curious as to what M57, her mate, is up to, and whether he is also in proximity to the den (if there is one…), since father wolverines play some role in protecting and raising their offspring. The precise parameters of this role are still up for debate, so if F3 is denning, it will be interesting to follow M57 as well. (Several days after we caught F3 last month, M57 also went into the trap; we didn’t have a collar ready and had to let him go, but he and F3 were at least relatively close to each other as of a few weeks ago.)

I waited to post this until today, since February 15th marks the close of Montana’s wolverine trapping season. Three wolverines in total were killed in the state this year, at least one of them a female. No wolverines were reported killed in region 3, where F3 and M57 live. I’ve had several comments over the past few weeks about trapping, and this is something I intend to write about soon, in connection with the broader issue of how we manage social conflicts around wildlife conservation. For now, I’m incredibly relieved that F3 and M57 made it through another year, and, although I am not opposed to the idea of hunting, and have a lot of respect for ethical hunters both here in the US and in Mongolia, I am also sorry for the loss of those three animals, for the sake of the overall wolverine population. I wish that Montana was crawling with so many wolverines that every trapper could take one and it wouldn’t even make a difference to the population at all. Unfortunately the scientific evidence points increasingly towards the fact that this is not the case.

What to Expect When Your Wolverine Is Expecting

Last Monday the Absaroka-Beartooth Project’s female wolverine F3 went into one of the project’s live traps in Montana. Jason Wilmot, Jeff Copeland, and several other participants drove up to re-instrument her. It was an early-season capture; usually wolverines hit the traps hard starting in March. Not for nothing are wolverines referred to as gluttons, so it’s hardly surprising that a gulo would grab an extra bite at any time of year, but a possible spur to F3′s early trap raiding became evident when the crew saw that her teats were enlarged; F3 is probably pregnant!

We captured F3 late last March and had to search through the fur of her belly to even find her teats; disappointingly, they were nearly non-existent, meaning that she was probably not pregnant and had not given birth last year. Understanding reproduction is the crux of the question of a species’ status, and with wolverines, data on reproduction are notoriously hard to obtain. Beyond the statistics, of course, a birth in any rare species is cause for celebration. F3 is about five years old, and although female wolverines reach sexual maturity at around two, most don’t reproduce until they’re three or four. We had high hopes for F3 when M57 moved into her territory two summers ago, but last year, although they had been in each other’s company during the breeding season, no kits appeared.

This didn’t mean that they hadn’t mated; wolverines, like other mustelids, bears, and several other mammal families, have a system of resource-governed pregnancy known as embroynic diapause or delayed implantation. A wolverine may mate and the eggs may be fertilized, but they don’t implant and develop until months later. If resources are too scarce and the female isn’t in good enough condition to bear and nurse young, the embryos dissolve without implanting.

Presumably in wolverines this reproductive strategy helps deal with the fact that the animals are sparsely distributed over the landscape; who knows when you’re going to meet again, so you might as well make every effort to insure the future of the species when you do run across each other. Delayed implantation probably also helps female wolverines cope with the sparsity of resources in their severe habitats; reproduction is hugely energetically expensive for any animal, and if the environment isn’t able to support a female through the intense periods of pregnancy and nursing, it makes no sense to put the energy into giving birth to young that will probably starve. Delayed implantation is a strategy that allows wolverines to fine-tune births to the best possible conditions for reproductive success.

Once implanted, gestation is quick, between a month and six weeks. The kits are born around Valentine’s Day, usually twins but sometimes up to four, deep in a snow den that the mother excavates. They are tiny, pure white, and helpless. A man who has kept captive wolverines for many years and has successfully facilitated a number of births says, as related in Doug Chadwick’s The Wolverine Way, that the kits are born with some sort of waxy substance on their fur and that this substance smells so horrible that it’s hard to get close to a newborn wolverine without getting nauseous. Presumably this, along with 10-foot-deep snow dens, is a defense against predation while the kits are vulnerable.

Female wolverines nurse their young for about three months, moving them among a series of dens before they emerge around mid-May. By this time, they are unrecognizable as the tiny white creatures born in February; they already have full gulo coloring and are close to adult size. They are not quite independent yet, though, and they stay with their mom through the fall. For the next year, still not quite ready to be on their own, they roam their parents’ territories and sometimes rejoin each other, their mother, or their father to play, to learn how to find particularly good carrion, to get some tips on hunting ground squirrels, or simply to pursue the mysteries of wolverine life in company. At the onset of full adulthood, around age two, they set off to carve out their own territories – if they survive. The Glacier National Park Wolverine Project recorded rates of juvenile mortality at around 50%; the world is a perilous place for a young wolverine. And then, even if a young wolverine makes it to its own new territory, it might still face what can be referred to as the M56 Dilemma; travel 500 miles across all kinds of obstacles, only to discover that the new territory is a little too vacant, and that there are no mates to be found.

Add to all these contingencies the fact that a female wolverine at peak condition and with all the resources she needs generally only produces kits every other year, and the survival of the species at all, let alone among widely separated mountain ranges, begins to seem miraculous.

The title of the blog post is something of an inside joke, because while I’m sure that giving birth provides its own sense of gratification to the female wolverine involved, wolverine researchers also have a distinct experience around wolverine pregnancy, and that experience seems primarily to be one of extreme uncertainty and a total suspension of expectations. The chain of uncertainty goes something like this:

Great! We have a male and a female wolverine hanging out together! Will they mate?

Okay, so if they mated, will she become pregnant, or will she resorb the fertilized eggs?

Wow, it looks like she might be pregnant! Will she manage to successfully den? Will she even give birth, since wolverines known to be pregnant in Glacier later appeared not to have had kits?

If she successfully dens and gives birth, will we be able to tell that she’s denning?

If she is denning, and even if we know she’s denning, will she be able to successfully nurse her kits until May?

If the kits live, it’s imperative to instrument them, because this will provide absolutely critical data on dispersal – but can we find the den?

If we find the den, do we have anyone seriously hardcore enough to get to it?

If we find the den and instrument the kits, will we be able to successfully track them, or will they disappear from the airwaves like so many other juveniles wolverines have done before?

Even if we have the human and technical capacity to do all of this, do we actually have the funding to pay for collars, implants, flights, and salaries?

These questions, no doubt, result in a number of sleepless nights for the expectant researchers; since the big news came in last week, I’ve already chalked up two. Wolverines are tricksters, and F3 in particular has had an uncanny knack for raising our hopes and then smacking them right back down. The uncertainty, though, is tempered by moments of euphoria, because if she is pregnant, and if she gives birth, and if we can instrument and track the kits, it’s a huge set of information on how wolverines function as a meta-population in the Rockies. Huge. And it’s worth all the uncertainty and the sleepless nights and the frozen fingers and toes and the near-death experiences if it can help in some way to tell us how to keep the species on the landscape over the long term.

So, F3 and M57, congratulations on your big news….if your big news is really the big news that we think it is. We will be eagerly waiting to find out.

Two bears and a collar

On Sunday afternoon, a growl yanked my attention from the undergrowth, at which I’d been peering intently; a few dozen yards from where I stood in a cluster of pine trees that opened onto an expanse of meadow high in the Absarokas, two bears were locked in what appeared to be combat, standing on hind legs, batting each other. One was pitch black, the other cinnamon. Their trajectory as they circled and growled and wrestled was straight towards me, although they hadn’t seen me yet. I beat a hasty, silent retreat up a nearby slope, slipping between blackened trunks of a burn, trying to keep one eye on the bears and the other on my footing. The telemetry antenna and receiver that I was carrying were awkward, and more so as I fumbled to make sure my bear spray was within reach. At the top of the slope, sweating and covered in ash and charcoal from the burn, I slumped against a charred tree trunk and began to take the antenna apart.

Back in March, en route to one of the research traps in Montana, Jason pulled over on the side of the road to test the GPS collar that we were about to put on M57. Jason tuned the telemetry receiver and then removed the magnet – which keeps the collar turned off until we’re ready to deploy it – and the steady pulse of the radio signal filled the cab of the truck. We drove on, and a few hours later, M57 took off into the trees, carrying the collar. It was scheduled to record locations via satellite every two hours. This allows a more refined understanding of how wolverines move over the landscape than radio telemetry locations, which are sporadic at best.

The collars that we’d put on M57 and F3 were scheduled to release in October, but by June 1st, both had managed to escape their collars; wolverines are notorious for their ability to do this. M57′s was relatively accessible; F3′s was further back in the mountains. I’d never been on a collar retrieval before, so I volunteered to go after M57′s. With telemetry receiver in hand, I figured it would be easy.

By the time the bears interrupted my search, I’d spent two afternoons in the vast meadow trying to pinpoint the telemetry signal, working off a single GPS point that the pilot had taken. It had been so easily within reach when Jason tested it back in the truck, a tame example of a technological object designed to do a task for humans, sitting benignly in the palm of Jason’s hand.

In the meadow, impossible to find and yet clearly somewhere nearby – the telemetry signal was persistent and loud – it seemed to have a devious life of its own, a capacity for illusion and elusion derived from the animal who had briefly worn it. I’d walk in the direction from which the signal seemed strongest; it would fade. I’d turn around and try again; the signal would appear to be coming from somewhere completely different. The previous afternoon a friend had gone with me, but even with her assistance in searching where I directed, we couldn’t find it. I was certain that Jason would have walked into the meadow and tracked down the collar within twenty minutes, but I’d never used telemetry to hunt for something in this way.

Preparing a collar for F3, March 2010

I’d finally found a strong signal and was following it downslope, closing in, when the bear juggernaut rolled across the meadow, across the path of the signal. The clock read 3:00 pm, and I had to be back in Jackson – many hours away – by the evening. I took it as a sign that the search was over. Sitting on the slope, I tried to keep an eye on each bear while simultaneously packing up the telemetry equipment. I accidentally kicked a few rocks downslope; the cinnamon bear froze and looked in my direction for a  second, before suddenly charging towards the black bear. The black bear evaded, and ran into the trees where I’d been standing looking for the collar. Summer, of course, is bear mating season, and as the black bear stood behind a tree and peeked out at the cinnamon bear, I realized that this could be courtship, which meant that I might be on the hill for a while. Then, the black bear turned and began walking up the slope towards me.

The telemetry equipment was still in disarray and at this point, I wasn’t sure where the cinnamon bear had gone; if I went down the other side of the hill, it might have circled around. I kicked a few more rocks loose, and then let the bear know I was there, speaking softly, which is what I had been told to do in a bear situation. Despite hours and hours on the trail, this was the first time I’d encountered bears out in the wilderness while alone. Black bears are much less intimidating than grizzlies, but I was still surprised by how calm and unthreatening the situation was. The bear looked up the hill, startled, and then wheeled and trotted into the trees on the far side of the meadow. I waited for a few more minutes, and when neither bear reappeared, I slid back down the ash-covered slope and then walked cautiously down through the meadow. The bears did not return. At the bottom of the meadow, I turned and asked that if either of them found a collar, they leave it there, so that when we came back, it would still be there to find.