Saturday, December 12, 2009

The Weasel: Black and White and Curious All Over

In my humble opinion, one of the most adorable animals in our Adirondack woods is the weasel in winter. To be more precise, it’s two animals: the short-tailed weasel, or ermine (Mustela erminea), and the long-tailed weasel (Mustela frenata). Both animals, with their pristine white fur, black-tipped tails, black button noses and alert black eyes, embody the essence of cute and curious, while at the same time filling the role of efficient predator.

Most of us, upon encountering a weasel, would be hard pressed to say if it was the long- or short-tailed variety, mainly because the encounter is likely to be fleeting. As the names suggest, the primary difference between these two mammals is the tail length: on the long-tailed weasel the tail is almost half as long as its body, whereas on the short-tailed weasel the tail is maybe a third of the body length. The short-tailed weasel is also the smaller of the two, but sometimes, without a side-by-side comparison, it can be difficult to tell which you have. According to D. Andrew Saunder’s Adirondack Mammals, the long-tailed weasel is the less common of the two species, but you couldn’t prove that by me, because I think every weasel I’ve encountered has been M. frenata.

Long and slender, weasels are ideal little predators. Their tubular bodies and short little legs enable them to flow easily across the landscape and into the dens of their favorite prey: mice and voles. But, just like any good predator, if the opportunity arises to take something larger, like, say, a gigantic snowshoe hare, it will. Food is food, and if the weasel can take it down, it will.

When it comes to energy conservation, however, this lithe body shape is far from ideal. If you look at most northern mammals, you see a tendency towards rounded body shapes, with abbreviated ears, short snouts, and short legs. Compactness is what it’s all about, for by being stocky an animal is better able to prevent heat loss during the long, cold winters. So how is the weasel, with its long body, short fur, and big ears, able to compensate? By feeding heavily and feeding often.

Many references, in describing weasels, refer to their tendency to partake in “bloodthirsty killing sprees.” This is really no more than an anthropomorphic description of an efficient hunting strategy. If you had to consume upwards of forty percent of your body weight every day just to stay warm, you’d probably do as the weasel does: take advantage of every prey item that passes your way. And if this means killing a whole family of mice when you are really only hungry for one, well, then you will just have to store the extra food away as insurance against lean times. Of course, this biological imperative is not likely to endear you to the farmer whose chickens you just wiped out.

While I know that weasels live in my neighborhood year-round, it really isn’t until winter that I become aware of their presence. As with all winter wildlife, any movement they make is recorded in the snow. The track pattern that catches the eye as distinctly weaselish is the 2×2 pattern, wherein you see two footprints side-by-side, followed by a space with no tracks, then another set of two. This pattern is made as the weasel leaps over the snow, its back humped slinky-like, its hind feet landing in the same pair of prints the front feet just made. Anyone who has had ferrets in his life knows exactly what this looks like (I used to have ferrets, so I speak from experience).

Winter is also when weasels are at their cutest, for it is now that they are all decked out in their splendid white fur. The only color that remains is the black tip on the tail, and the alert black eyes and little black nose. In the summer, the only white they sport is the fur on their bellies, the rest of their pelage being a basic brown (the tail keeps its black tip, regardless of the season). A weasel discovered in the spring or fall is likely to be a mottled mix of brown and white as the animal goes through its change. In the fall, the brown fur is shed and the new fur grows in white, thanks to hormones turning off the production of melanin, the pigment that determines coloration in fur (and hair, eyes, and skin). Come spring, the process is reversed and melanin is turned back on, causing the new fur to grow in brown as the white fur is molted out.

But why change color at all? It’s all about camouflage. Because it is constantly on the move looking for its next meal, a weasel’s cryptic coloration isn’t designed to improve its odds as a predator. Instead, it serves to help it avoid becoming dinner for something bigger, like a coyote, hawk or owl. This is also where the black-tipped tail comes into play. In one account I read, a hawk was presented with a stuffed weasel that had no black-tipped tail. The hawk attacked this presumed-food item on the head every time. When presented with a stuffed weasel that had a black-tipped tail, the hawk hesitated before striking (weasel has more time to escape) and then, more often than not, attacked the tail end (increasing the odds of weasel survival).

If you’d like to bring weasels to your property this winter, you can try putting out stashes of suet near good weasel habitat, such as brush piles. If there are weasels around, this will likely draw them out, for they are highly inquisitive animals and suet is a high-energy food source that will not fight back if pounced upon. Of course, you might have to fend of squirrels and other wildlife that are also attracted to your bait station. I may try this myself this winter, once the bears are denned down, and see if I can finally capture a photograph of weasel in its winter whites.

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Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.





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  1. Ellen Rathbone says: