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Serving Northern St. Louis County, Minnesota

Weasel’s winter white

For this member of the genus Mustela, it’s all in the tail

Marshall Helmberger
Posted 1/27/21

I was surprised the other morning by the little white head that popped up from under the remains of the rib cage of the deer I shot this fall. The rib cage, or at least the remains of it after …

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Weasel’s winter white

For this member of the genus Mustela, it’s all in the tail

Posted

I was surprised the other morning by the little white head that popped up from under the remains of the rib cage of the deer I shot this fall. The rib cage, or at least the remains of it after we’ve cut all the meat that’s readily accessible off the bones, has been lying out on the big rock that sits just outside our west picture window. So far, it’s mostly attracted the attention of jays, woodpeckers, chickadees, and the occasional bold raven that doesn’t mind getting so close to the house.
This time, however, it was a furry neighbor who had decided there were still enough bits of something to pry from between the ribs. Dressed in its winter white, it was a short-tailed weasel who’d come calling, and he was making the most of the situation. His sharp teeth and strong jaws were able to shear off bits of fat and meat that the birds hadn’t already pried off long ago. With every mouthful, he’d disappear momentarily under the big rock, presumably to cache his latest booty. Then he’d bound, seemingly effortlessly, up the side of the rock for another go at his bony prize.
While I presumed our visitor was a short-tailed weasel, I actually had to do a little research to confirm it. We have three species of the genus Mustela here in the North Country, including the least weasel, the short-tailed weasel, and the long-tailed weasel.
It was obvious this wasn’t a least weasel, which lives up to its name as a truly tiny little carnivore. Females range in length from just four and a half inches to about eight inches, while the males average between five inches up to about nine inches, nose to tail tip. And unlike the other two members of its genus, the least weasel lacks the black tail tip that was readily apparent with our visitor.
The short-tailed weasel is smaller, on average, than its long-tailed cousin, but the size ranges of the two species overlap quite a bit, so it’s not always a good indicator. As with other members of the mustelid family, which includes marten, fisher, mink, and otters, the males of the species are considerably larger than the females, so the potential variability in size within each species is quite substantial.
Both the short-tailed and long-tailed weasels have the black-tipped tail, which remains whether they are in their summer brown coat or their winter white. The only field mark that’s reliable is the length of the tail. Tail length averages about one third of body length in the short-tailed weasel, while the tail reaches at least 50 percent of the body length in the long-tailed variety.
Based on that characteristic, I could safely identify our visitor as a short-tailed weasel.
Weasels are aggressive predators and they are known to prey most readily on other small mammals, like mice and voles. When they are successful, they are known to cache leftovers for later consumption. I’ve run into these caches a time or two over the years, and they can appear fairly grisly. Once, I found eight star-nosed moles stuffed tightly into two old engine cylinders I had stuck in a box in the garage after rebuilding an old VW engine— a sure sign of an industrious weasel.
While they’re aggressive predators, weasels are so small that they also frequently become prey, which is probably one reason they never seem to relax. They’re constantly on the lookout for something larger, like a hawk, owl, or pine marten, headed their way. Their shift to a white winter coat is almost certainly more a factor of protecting them from other predators than it is to hide their approach in the snow. In fact, in winter, weasels spend a lot of time under the snow, following the tunnels left behind by their small mammal prey. All that most of their victims would ever see of a weasel under the snow are their black, beady eyes, pink nose, and sharp teeth. And, by the time they see that, it’s pretty much all over.

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