Description: A large aquatic rodent whose long, flat tail undulates from side to side when it swims. Total length 18 to 25 inches. Tail 8 to 11 inches. Weight 2 to 4 pounds. The thick, dark brown fur of the upper body is overlaid with brown to black guard hairs. The legs are short but powerful. The front feet are small, but the hind feet are relatively large and partially webbed, with stiff hairs on the edges of the webs and along the sides of the toes. The long, black tail is flattened vertically. It is so scantily haired that it may be said to be naked, but is covered with small scales up to 2 millimeters in diameter. The head is quite similar to that of a vole. The ears are so short as to barely protrude through the fur, and the eyes are small. Average number of young thought to be six per litter. Several litters may be born each year. The presence of muskrats in a shallow lake or marsh is not difficult to detect. This is their chosen habitat, and here in water about 1½ feet deep, they build their characteristic mounds of rushes and cat-tails. Here they may also be seen on quiet days swimming about and carrying on their normal activities. In much of the Southwest, however, such favorite habitats are few and far between and the muskrats must take their choice, if there be one, between the few permanent streams and irrigation canals. In these altered circumstances they react quite differently; they may often be present in considerable numbers without anyone being the wiser. The change in habits required by this different environment illustrates the great adaptability exhibited by many of our most common mammal species. The most important requirement of a muskrat is a permanent body of water of a depth sufficient for it to dive into and escape from its enemies. Given this, it will at once set about constructing a home. In a lake or marsh, there is little or no current. In sheltered bays, where wave action is slight, the bottom often will be muddy. In the shallow water along the shore, water plants such as tules and cattails will become established. This is indeed muskrat heaven, for these and other aquatic plants are both their food and building materials. The most edible portions of the plants are the roots and the stem portions which are below the surface of the mud. When one of these choice tidbits has been cut free by the muskrat’s sharp teeth, it is carried to some favorite place to be eaten. This may be a mud bar well sheltered by overhanging vegetation from prying eyes, the end of a log projecting above the surface of the water, or perhaps the roof of the “house.” The discarded portion of the stem is buoyant and usually lodges among the remaining plants until needed for building purposes. [Illustration: muskrat]