Biology Reference
In-Depth Information
his flock of hens dead, the damage done to poultry by weasels was always minor compared to the good
they did—and continue to do—in controlling mice, rats, and other rodents.
The notion that weasels are evil, cold-blooded creatures that kill for the sheer joy of killing stems
from ignorance of their requirements for survival, fortified by a substantial dollop of anthropomorph-
ism. Life is precarious for any wild creature, predator and prey alike, but especially for the weasel in
winter. Consider some of the impediments to weasel survival during this harsh season.
First, the long, slender head and body, which enable a weasel to go most places where a mouse can
go, are also very inefficient at preserving body heat; this problem is exacerbated by a thin fur coat
and very little body fat. Second, the weasel is hyperactive, with a heartbeat in the hundreds of times a
minute, so it takes a great deal of fuel to stoke its tiny furnace. Meanwhile, the pool of available prey
steadily shrinks because young are rarely born during the winter months, while disease and predation
take a constant toll.
Together, these ingredients form a recipe for weasel disaster—and in fact winter starvation is prob-
ably the major cause of weasel mortality. Against this formidable array of problems, evolution has pro-
grammed weasels with an effective survival strategy. This is known to biologists as “surplus killing,”
the trait that has given the weasel such a sinister reputation.
Because weasels live on the ragged edge of starvation, especially in winter, they kill as much prey as
they can find; any surplus is cached and enables the weasel to endure at least a short period of unsuc-
cessful hunting. Naturalists, incidentally, noted this caching behavior at least a hundred years ago.
Thus a weasel that slaughters a flock of hens in the coop is simply obeying an instinct. Its actions
have nothing to do with taking pleasure in killing and everything to do with evolutionary programming
that has enabled the species to survive.
Weasels customarily kill by a bite at the base of the skull, or close by in the neck. No doubt this fact,
coupled with their penchant for surplus killing, led to the idea that weasels suck the blood of their vic-
tims, like minuscule vampires sprung to life out of some horror movie. A farmer finding his coop filled
with dead chickens, uneaten but with tiny puncture marks in the neck, could be forgiven for assuming
that the weasel was simply dining on blood.
Weasels have also been accused, from time to time, of sucking the contents out of eggs. In
As You
Like It,
Shakespeare penned the words, “I can suck melancholy out of a song as a weasel sucks eggs.”
Unfortunately, the Bard was far off base with this analogy.
There are three species of weasels native to North America. In order of size, they are the long-tailed
weasel
(Mustela frenata),
short-tailed weasel or ermine
(Mustela erminea),
and least weasel
(Mustela
rixosa).
The long-tailed weasel is found throughout most of the continental United States, except for Alaska,
as well as a little of southern Canada. The short-tail's range is more northerly, encompassing even far
northern Canada. It overlaps the long-tail's range in southern Canada, throughout New England, New
