Building the perfect weasel
Cold temperatures are best endured by those of some rotundity, those with a low surface to mass ratio. If you were to design a creature to endure the thermal challenges of winter, roly-poly would be a good basic shape to start with. Cold is not the only challenge posed by winter, however, finding sufficient calories is equally daunting.
One of the most abundant, high-energy, easily assimilated foods, available year round, comes in furry little packages that can be found living beneath the snow -- those tiny mammals of celebrated fecundity, the mice, voles and shrews. A creature able to enter that world beneath the snow would eat well indeed, and would have access to some of the warmest shelter available, too. Perhaps portliness is over-rated as a design for winter survival.
Let us return to the drawing table and instead draft plans for a miniature carnivore, low and slim, that can enter the dark, close realm beneath the snow. Let us give this little hunter eyes that see well in the light and the dark, a keen sense of smell and good hearing, hearing that includes the high frequencies of small mammal vocalizations. Let us give it boundless energy and curiosity, and just for the heck of it, enduring playfulness.
You see where I’m going with this; we are, of course re-inventing the weasel. Access to the caloric jackpot of tiny mammals stokes the weasels’ furnace through the cold season, and provides the energy needed to travel to find enough to eat. Weasels eat about 40 percent of their body weight in food each day, divided into five to 10 meals.
This year has been an especially good year to be weasel-shaped, since it was also a very good year to be a rodent. After two years of abundant seed production and a fairly easy winter, the mice, voles and squirrels were able to raise many offspring. These fueled a successful child-rearing season for the weasels.
I have seen film footage of baby weasels. The eight fuzzy wrigglers in their nest of fur and feathers kept up a din of chirps, trills, and squeaks. Later they emerged from their den, leaping and wrestling and continuing the chatter. In the final film sequence, the young weasels set began to explore the surrounding territory, bounding off in tight formation like a tiny roiling river, pausing in synchrony every few seconds, all heads periscoping up on long necks.
Two weasel species can be found in our environs. The long-tailed weasel, Mustela frenata, is the largest, with males about 16 inches in length and weighing about the same as a red squirrel. The females are a few inches shorter and typically weigh less than half as much as the males. The short-tailed weasel, Mustela erminea, is a dainty beast. A female might be just seven inches long and will weigh less than a chipmunk. Males are typically closer to 11 inches in length. Their paired footprints are so tiny, just an inch or two wide, that they can be mistaken for those of mice or shrews in soft snow.
As the names suggest, tail length helps distinguish the two species; the short-tailed weasels’ tail is about a third of the length of the rest of the body, while the tail of M. frenata is half the length of the rest of the body. In the summer both weasels are a dull, leaf litter brown with a white or cream-colored belly and a black tail tip. In the winter, both weasels don elegant white coats and keep the black tail tip. This white coat with the black tail tip is the fur known as ermine (ermine is also another common name for the short-tailed weasel). Ermine is the fur that adorns the raiment of royalty, snowy white accented by the black tail tips.
Of course if I were in charge of designing animals, I wouldn’t make any carnivores at all. It is just as well that I’m not, for I admit it would be a less wondrous planet without such beasts as owls and bobcats and foxes. My ambivalence about carnivores has grown since I have developed relationships with many herbivores, among them Priscilla, the gray squirrel that I raised as an orphan a few years ago. She is a very regular visitor to my house, and I take a keen interest in her activities and welfare.
One afternoon I saw the very fresh tracks of a weasel in my yard, and the scene of a kill, a large bloodstained depression in the snow. The tracks leaving the scene recorded the very short bounds and drag marks of a heavily laden weasel. Priscilla did not appear again for an unprecedented six days, but appear again she did. The weasel, it seems, had taken care of a moral conundrum for me by dining upon the very large rat that had moved into my hay shed.
On a recent day of mild weather, as Priscilla and the other squirrels were celebrating the break from the cold, I saw a flash of white leaping across the yard. The weasel’s tracks led over a steep bank and into a tunnel in the snow. While Priscilla lolled in a tree overhead, idly nibbling on bark and buds, I admired the weasel’s neat footprints. When next I looked up, weasel and I were staring at each other from a distance of five feet. The weasel’s black eyes and nose formed a neat equilateral triangle against the pure white of her fur, so alert, so poised, so beautiful. Here was perfection.
The weasel did not find my appearance as captivating, little wonder. She wheeled and bounded back into a tunnel. As I stood guard beneath my squirrel friend, I thought about kings and queens with their vanities and human foibles, and knew that I had just seen the only creature truly worthy of wearing an ermine coat.
Patti Smith is a naturalist at the Bonnyvale Environmental Education Center. The View From Heifer Hill appears in this space the first Saturday of each month. Patti welcomes your feedback at firstname.lastname@example.org.
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