Last weekend, there was a tussle in the lilac bush in our front yard, and when the snow settled, what was revealed was one weasel and one very agitated red squirrel. The weasel ducked into the shed. The squirrel hopped onto a branch and unleashed a sermon of chittering vitriol, which I believe roughly translated as: How dare you trespass when I was just about to eat that weasel? Never underestimate the ego of a red squirrel.
There’s no need to pity the weasel; unbeknownst to me, the kids snuck out sympathy bacon, which the weasel promptly consumed. Here’s a photo of what’s likely the same animal later that day, and a photo of the winter lodger in our shed, a Virginia opossum. With a blizzard looming for much of the Northeast, now seems a good time to make a point about wildlife and winter adaptations, which these creatures model perfectly.
One of the tropes of wildlife documentaries is that evolution has polished every species into perfect adaptation to its environment. But of course that isn’t true. Every animal’s body expresses where it came from, evolutionarily speaking, and represents a trade-off of survival traits and sacrifices.
Look at the weasel. It’s an ice age carnivore descended from earlier marten types, and its body expresses generations of chasing mouse-like creatures under snow. That long funnel shape can follow anywhere its tiny skull can fit. Its flexible spine and stubby legs allow it to flow through tight, twisting spaces, and – another adaptation to tight spaces – its muscled neck allows it to carry prey out in front of its body, instead of a more typical carnivore pattern of dragging prey against its chest. But this design has a major liability for the weasel: it has no fat on its slinky body. If it doesn’t bring home the bacon, quickly and frequently, it starves.
Now check out the opossum. Everything about its ridiculous looks says, “summer.” For starters, its bare tail and ears both seem designed for heat loss and a quick case of frost bite. While this particular opossum is the fuzziest I’ve ever seen, it still sports a pretty sparse winter coat.
As its appearance suggests, this creature comes from a different landscape than the weasel, and its recent success in the Northeast appears in part due to a knack for taking advantage of human-made food and shelter. Interesting note: While a newcomer to our region, the opossum’s lineage is ancient; fossil records suggest that opossum-like creatures split off from other marsupials around 65 million years ago, right about the time the last dinosaurs died, and they’ve been waddling around North America ever since. This long acquaintance with reptiles is also the reason for one of the opossum’s most remarkable features: a resistance to snake venom, which is an utterly pointless trick for the little guy in our Vermont shed.
So there you have it: an animal odd couple, both eking out a living in our habitat, but neither perfectly built for survival. It’s worth noting as well that, while the opossum’s reliance on humans is obvious, the weasel has also found an opportunity to reap some benefits. As Robert Thorson noted in this popular The Outside Story article from 2018, stone walls provide approximately 100,000 miles of special habitat in New England alone – a boon for mouse hunters.