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.