It’s February 14th once again, which, as everyone knows – or should know – is a very important day: Wolverine Birthday. This is the approximate date of birth for wolverines all over the world. Mid-February marks the descent of pregnant female wolverines into their snow dens, there to give birth and attempt to raise their kits, moving them uphill through a series of maternal dens until they are big enough to emerge. This happens sometime in late spring, usually mid-May, after which the kits hang out in their parents’ territories, sometimes alone, sometimes following their mother, sometimes their father, until they set out to find a territory of their own, about a year after they’re born.
At least, this is the basic outline of the first year of a kit’s life. Bob Inman and Audrey Magoun published a paper in 2012 reviewing all recorded wolverine births, as well as information obtained from trapped carcasses of pregnant or lactating females, and the birth dates generally ranged from late January through mid-March, with reports from the 1950’s of wolverines giving birth as late as April. So the February 14th date is a handy mnemonic device that doesn’t necessarily reflect an absolute reality. The lack of an absolute reality is interesting, as are the reports of much later births earlier in the century and further to the north. Wolverines mate in the summer, but the fertilized embryos don’t implant until later. The exact triggers for implantation (the technical term is nidation) remain unclear, but probably have to do with the female’s body condition – without a certain level of fitness on the part of the female, the embryos will simply dissolve without ever implanting. The range of birth dates means that there is also a range of nidation dates, which could be solely dictated by the percent body fat of the female – or could also be triggered in part by environmental factors. Maybe, then, there’s some range of potential adaptation to changing climate conditions? This is speculative, of course, but if it turns out to be true, it’ll make my valentine’s day every year for the rest of my life.
All of this just complicates my agenda to turn an otherwise annoying holiday into something with real meaning, however. So for now, let’s just stick with February 14th, and I hope everyone out there is having a great Wolverine Birthday. More posts soon!