Biology Reference
In-Depth Information
tail can present a rather comical appearance: when the muskrat is floating at rest, it sometimes angles
its tail upward, completely out of water. There, unsupported, it forms a shallow curve, first upward and
then, farther back, gradually drooping toward the surface.
Meanwhile, the muskrat's admirable fur coat protects its owner against the effects of even the most
frigid water. Although muskrat fur isn't quite as highly prized as that of the beaver, it's nonetheless
very handsome. Beneath the long, dark brown, glossy outer guard hairs lies a dense coat of fine, soft,
grayish underfur, designed to keep water away from the muskrat's skin.
Because of the high quality of their pelts, muskrats have long been a staple of the fur trade in North
America. In Wisconsin, for example, the value of muskrat pelts from 1970 to 1981 exceeded $33 mil-
lion. Despite being both extensively and intensively trapped each year, however, the muskrat has re-
mained abundant down through the years and continues to thrive. This is due to a combination of the
muskrat's adaptability and its exceptional reproductive capacity, which is far more like that of the vole
than the beaver.
For an animal of its size—two to four pounds—the muskrat has a remarkably short gestation period,
lasting a little less than a month. Further, it has at least two litters annually, often three, and sometimes
as many as four, with most litters consisting of four to eight young. Add the fact that a female muskrat
can breed as early as eight months, and the biological potential of a pair of muskrats, if completely un-
checked, is astronomical!
Obviously, many influences restrain the growth of muskrat populations: otherwise we'd be knee-
deep in muskrats. Disease, parasites, injuries, and predators all take a toll. Humans are now a major
predator of muskrats, but mink are also an important natural enemy. Thoroughly at home in the water,
mink often enter muskrat houses in search of a meal. There, despite being much smaller than an adult
muskrat, these fierce little predators quickly do away with the occupants and dine in style. Otters, too,
even swifter and more at home in the water than mink, sometimes prey on muskrats.
Other predators also abound, though they mostly prey on young muskrats. Big snapping turtles and
large fish, such as northern pike and garfish, relish young muskrats and feed on them at every oppor-
tunity. Raccoons, hawks, great horned owls, and alligators also esteem muskrats as food. All in all, this
system of muskrat fecundity and numerous predators seems to work very well, as muskrats are neither
scarce nor overabundant in most locations.
If there's any threat to the muskrat, it's habitat loss. Despite its adaptability, the little marsh dweller
can't survive without suitable areas for food and shelter. Habitat loss comes from two sources. The first
is the continued drainage of wetlands for everything from agricultural land to development. Although
laws protecting wetlands have helped to slow the destruction of our enormously important wetlands,
they haven't yet halted it.
The second major source of habitat loss for muskrats comes from the nutria, or coypu
(Myocastor
coypus),
a rather large rodent that weighs fifteen to twenty pounds. It was unwisely imported from
South America for its fur, and its introduction has had serious repercussions for both marsh and marsh
dwellers. The nutria is found mostly in coastal areas in Maryland and Delaware, from Georgia to
