Biology Reference
In-Depth Information
Not only are muskrats more flexible than beavers in regard to food and habitat, but they're also less
choosy about living quarters. A beaver is compulsive about building a lodge, and digs a tunnel into a
bank only as a last resort in situations where constructing a dam or lodge is totally impractical. Even
in a large body of water with an outlet that beavers can't possibly dam, the big rodents will fabricate
a lodge near shore, provided the shoreline doesn't drop off too abruptly or isn't excessively rocky. A
muskrat, on the other hand, usually lives in a burrow by preference, but is perfectly at ease building a
house in marshes where there are no convenient banks steep enough for burrowing.
A muskrat burrow can be quite long—up to fifteen feet—angling up and back from just below the
surface of the water. With a larger living chamber at the end, and several escape tunnels, the whole af-
fair can be fairly elaborate. Although muskrats are generally very beneficial, their tunneling proclivities
sometimes cause damage to dikes and small earthen dams, making them unwelcome residents in some
situations.
A muskrat house is much less strong and elaborate than a beaver lodge. These little domed structures
are made in autumn by heaping up a mixture of reeds and mud. The muskrat then burrows up into the
mass from below the waterline, excavates a chamber, and digs out additional tunnels for escape routes
beneath the water.
Next the muskrat erects several smaller, ancillary structures within a few yards of the main lodge.
These little affairs, called
pushups,
enable the muskrat to extend its feeding range when the marsh or
pond is icebound. In late fall or winter, after the marsh vegetation has died down, these houses and
pushups can be seen dotting large marshes, protruding above the water or ice.
Muskrats even manage to find housing in large swamps that lack banks for burrowing and cattails or
similar vegetation for constructing houses. In that event, a muskrat will utilize a hollow log or stump,
proving once again how adaptable a creature it is.
Muskrats are an extremely important component of many wetlands. Where they're abundant, they
consume an enormous amount of aquatic vegetation, particularly emergent species such as cattails.
Without these industrious little harvesters, many wetlands would have almost no open areas, because
cattails and similar plants would soon choke out most of the open spaces. Indeed, the percentage of
open water in a marsh is often highly dependent on the muskrat population.
This propensity for creating openings in wetlands makes the muskrat extremely valuable to other
species. Without open areas, ducks, geese, herons, egrets, and numerous other birds would derive little
benefit from marshes, shallow ponds, and similar wet areas. Moreover, areas of open water create
places for a variety of submerged aquatic plants to grow, thereby contributing greatly to the wetland's
diversity.
Unlike beavers, muskrats seem to have little territorial instinct except in connection with their actual
homes. This trait makes excellent evolutionary sense when one thinks about it: if muskrats were as
fiercely territorial as beavers, they would be in constant conflict, and it would be very difficult for large
numbers of them to coexist in the same marsh.
