Biology Reference
In-Depth Information
York, and Pennsylvania, in the Great Lakes region, and in much of the area from the Rocky Mountains
westward. The least weasel's range takes in Alaska and most of Canada except its far northern reaches,
avoids New England and New York, then extends down the Appalachians and across the northern half
of the United States to roughly the Rocky Mountains.
The long-tailed and short-tailed weasels are quite similar in appearance and habits, and they can be
very difficult to tell apart except on close inspection, especially in their white winter phase. In their
summer brown, however, short-tails can be distinguished by their white feet, which are lacking in the
long-tails.
Long-tails are generally larger than short-tails (up to seventeen or eighteen inches long, including the
tail, compared to thirteen inches for short-tails). Size, however, is not a very good criterion for quick
identification; since male weasels are much larger than females, a large male short-tail can be as big
as a small female long-tail. An average long-tail weighs eight ounces or less, an average short-tail less
than half that.
Both species have a black tip on the tail. Except for this tip, the short-tail turns white in winter
throughout most of its range. This, of course, is the famous ermine that long graced the robes of royalty.
The long-tail also turns white in the more northerly parts of its range, where there is usually snow dur-
ing the winter, and the white pelts with black tail tips of both species are considered ermine in the fur
trade.
The white winter coat makes eminent good sense in an evolutionary scheme. Weasels are the target
of numerous predators—hawks, owls, foxes, coyotes, and domestic cats among them—and the weasel's
white fur against a snowy background provides excellent camouflage.
But what of the black tip on the tail, which would seem to defeat the weasel's camouflage? Scientists
long puzzled over this seeming anomaly. Then a researcher named Roger Powell wondered if perhaps
the black tip of the tail drew the attention of predators away from the weasel's body. Using captive
hawks trained to attack fake weasels “running” across a white background, he found that the hawks
repeatedly attacked the black tip of the tail, rather than the “weasel's” body. When the black tip was
eliminated, the frequency of successful body attacks increased.
Although long-tailed and short-tailed weasels are very small, they are veritable giants compared to
the aptly named least weasel. The smallest of the world's true carnivores, this minuscule predator is
only six and a half to eight inches long, including tail, and may weigh barely more than one ounce! It
turns white in winter throughout all but the most southerly portion of its range. Curiously, however, its
tail lacks a black tip; biologists believe that with a tail only one and a half inches long or less, a black
tip would draw attacks too close to this tiny weasel's body.
Starvation and predators are by no means the only dangers confronting weasels. Although they're
predominantly predators of mice, voles, and other small prey, weasels also attack larger animals such as
rats and rabbits. Even the most peaceful of animals will defend itself with desperate courage and energy
when cornered; hence weasels sometimes suffer fatal wounds when they attack prey many times their
