muskrat, North American aquatic rodent. The common muskrats, species of the genus Ondatra, are sometimes called by their Native American name, musquash. They are found in marshes, quiet streams, and ponds through most of North America N of Mexico, but are absent from the extreme W and SE United States. A common muskrat resembles a large house rat with its tail flattened on either side; its hind feet are partially webbed between the toes. Its outer fur is shiny brown, and it has a dense undercoat. Its body length is 10 to 14 in. (25-36 cm), excluding 8 to 10 in. (20-25 cm) of tail. Its shoulder height is about 5 in. (13 cm), and its weight is 2 to 3 lb (0.9-1.4 kg). A solitary dweller, it may live in a burrow in a steep bank or a reed hut built in marshy shallows. Muskrat burrows are constructed above water level and are connected to an underwater entrance by a tunnel; huts are built with an underwater opening. Muskrats do not build dams or fell trees as do beavers. They swim by paddling with the hind feet, using the tail as a rudder. They feed on vegetation and aquatic animals; their chief enemy is the mink. Mating occurs in spring and summer. The gestation period is about 30 days and the female bears several litters of two to six young each season. Muskrat fur is much used commercially, chiefly for women's coats. It is often dyed to resemble more expensive furs and is sold under a variety of names, including Hudson seal and river mink. The secretion of the musk glands is used in making perfume. Introduced into Europe for its pelts, the muskrat became a serious pest because its tunneling below water level undermines canal banks and dike foundations. The round-tailed muskrat, or Florida water rat, Neofiber alleni, is found in swampy regions of Florida and SE Georgia. It dives and swims well, but is less aquatic then the common muskrat, spending much time on land. It is about 12 in. (30 cm) long, including the long, scaly tail. It is about 2 in. (5 cm) high at the shoulder, and weighs about 3/4 lb (0.34 kg). Its feet are not webbed, and its tail is not flattened. Despite their greater size and longer tails, muskrats are closely related to voles. The water vole, Arvicola, found in most of Europe and N and W Asia, is an intermediate form; it is longer than other voles and in parts of its range leads an aquatic existance. Muskrats are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Cricetidae.

Either of two semiaquatic, brown rodent species (family Cricetidae) native to marshes, shallow lakes, and streams of North America and introduced into Europe. The compact, heavy-bodied muskrat, or musquash (Ondatra zibethica), is about 12 in. (30 cm) long, not including the long, scaly, flat tail. The partially webbed hind feet have a stiff, bristly fringe. Anal sacs produce a musky secretion. The commercially valuable fur consists of long, stiff, glossy guard hairs overlying a dense, soft underfur. Muskrats live in either a burrow dug into the bank or a reed-and-rush mound built in the water. They eat sedges, reeds, roots, and an occasional aquatic animal. The round-tailed muskrat, or Florida water rat (Neofiber alleni), is smaller.

Learn more about muskrat with a free trial on Britannica.com.