• Adult total length: 21 1/4 - 25 in. (545 - 640 mm)

• Tail: 9 3/4 - 11 in. (250 - 283 mm)

• Hind foot: 3/4 - 7/8 in. (18 - 21 mm)

• Weight: 1 1/3 - 4 lbs. (0.6 - 1.8 kg)

• Physical Characteristics: The muskrat is a large semi-aquatic rodent. The upperparts are covered with soft, dense, glossy brown underfur and reddish-brown or black guard hairs. An albino muskrat with snow-white fur and pink eyes was recorded along Cosby Creek (Linzey, 1995b). The underparts are whitish or pale brown. The eyes and ears are small, and the hind feet are partially webbed. The tail is long, sparsely haired, and laterally compressed. The hind feet and tail serve as oars and a rudder when swimming. Orange enamel covers the front surfaces of the large incisor teeth. The lips are able to close behind the incisor teeth so that the muskrat can gnaw while underwater.

  Muskrats possess a pair of musk glands which enlarge during the breeding season, especially in males. These glands emit a musky yellowish secretion. The name muskrat is derived from this musky odor and the animal's ratlike appearance.

left lateral view of skull and mandible	dorsal view of skull	ventral view of skull

• Range Maps

  North America	Great Smokies

• Great Smoky Mountains National Park: Muskrats are found primarily in the larger streams and are fairly common below 2,400 feet. Park records, however, contain two unusual high elevation records. A young muskrat was observed on the Rainbow Falls Trail (5,300 feet) in April, 1949 (Tanner, personal communication to Stupka, April 28, 1949). In March, 1951, an individual was found dead on the Tennessee side of the Newfound Gap Road (4,500 feet) (Stupka). It is thought that these were wandering individuals.
  • Blount Co.: Mouth of Abrams Creek; West Prong of the Little Pigeon River (1,600 feet); Cades Cove (1,800 feet).

  • Cocke Co.: Cosby Campground along Cosby Creek (appoximately 2,400 feet).

  • Sevier Co.: Greenbrier Cove (1,350 feet); Elkmont; Newfound Gap Road (4,500 feet); Rainbow Falls Trail (approximately 5,300 feet).

  • Swain Co.: Deep Creek; Indian Creek; Forney Creek; Ravensford; 2 miles up Bradley Fork and Oconaluftee River from Smokemont.

Index

Natural History

• Reproduction
  Except during unusually cold winters, muskrats breed year-round. In the park, most muskrats are born during April and May, although some breeding also occurs in August and September. Gestation varies from 25 to 30 days. Most litters consist of three to five young. Immature muskrats have been recorded April 27 and August 29 ( Linzey, 1995b).

  Newborn muskrats have their eyes and ears closed, are sparsely haired, and have a round tail (Errington, 1939). They weigh approximately 21 g. The body is well-haired by the end of the first week, and the eyes open between 14 and 16 days. Immediately before the eyes open, most of the young are able to swim and dive. The young are weaned in about one month and move to new living quarters at about this time. The tail becomes laterally compressed during the second month (Errington, 1963). Muskrats are approximately adult size in five to eight months but probably do not breed until the following year.

• Longevity
  Although the mortality rate of young muskrats is quite high, some wild individuals have been known to live for four years (Linzey, 1995a).

• Terrestrial Ecology
  Muskrats are chiefly nocturnal but may be active at any hour of the day or night all seasons of the year. Evidence of muskrats consists of conspicuous houses, trails, and piles of cut sedges and cattails in a marsh. Muskrats may build houses of sticks, grasses, rushes, leaves, and mud, or they may excavate a burrow in the bank. Houses may range from 3 to 9 feet in diameter at the base and rise 2 to 4 feet above the surface of the water. Each house has one or more underwater entrances and one or more dry chambers.

  Muskrats are not especially sociable, although several adults may live in one house during the winter. In summer, a den is usually occupied by only one family.

  The muskrat is an excellent swimmer and diver and can travel 55 m underwater without coming up for air. It can remain underwater up to 20 minutes and can swim backwards or forward. In swimming, the muskrat uses only its hind feet for propulsion, holding the forefeet motionless under the chest. The tail is used extensively when swimming underwater. The muskrat's sight, hearing, and sense of smell are poor, but it has an uncanny sense of direction (Linzey, 1998).

  Unmated males wander in the spring, but otherwise, muskrats usually remain in the same general location throughout the year. Muskrats are primarily vegetatians and feed on the stems, leaves, and roots of many plants. Their diet may also occasionally include crayfish, other invertebrates, fish, frogs, or turtles (Linzey, 1995a).

  Komarek and Komarek (1938) reported muskrats feeding on willow ( Salis sp.). A large patch of corn was destroyed by this species near Ravensford (Linzey, 1995b). A muskrat reportedly captured and carried off a stoneroller minnow (Campostoma anomalum) near Gatlinburg (Stupka, 1961).

• Predators and Defense
  Hawks, owls, foxes, raccoons, and mink are the muskrat's chief enemies.

• Parasites
  None recorded from the park.

• University of Michigan, Museum of Zoology
• eNature

Index

Acknowledgements

• Text
  • Dr. Donald W. Linzey, Wytheville Community College - wclinzd@wcc.vccs.edu
  • Christy Brecht, Wytheville Community College - wcbrecc@wcc.vccs.edu

• Photographs
  • Roger Barbour

• Map development
  • Richard Schulz, Great Smoky Mountains National Park - richard_schulz@nps.gov

• Web page design & coding
  • Denise Lim, University of Georgia, Athens
  • John Pickering, University of Georgia, Athens

• Errington, P.L. 1939. Observations on young muskrats in Iowa. Journal of Mammalogy 20 (4): 465-478.

• Errington, P.L. 1963. Muskrat Populations. Ames: Iowa State University Press.

• Feldhamer, G.A. 1999. Muskrat. Pages 652-653. In: D.E. Wilson and S. Ruff (eds.) The Smithsonian Book of North American Mammals. Washington, D.C: Smithsonian Institution Press.

• Komarek, E.V. and R. Komarek. 1938. Mammals of the Great Smoky Mountains. Bulletin of the Chicago Academy of Sciences 5 (6): 137-162.

• Linzey, D. W. 1995a. Mammals of Great Smoky Mountains National Park. Blacksburg, Virginia: The McDonald & Woodward Publishing Company, Inc.

• Linzey, D. W. 1995b. Mammals of Great Smoky Mountains National Park-1995 Update. Journal of the Elisha Mitchell Scientific Society 111(1):1-81.

• Linzey, D.W. 1998. The Mammals of Virginia. Blacksburg, Virginia: The McDonald & Woodward Publishing Company, Inc.

• Stupka, A. 1935-1963. Nature Journal, Great Smoky Mountains National Park. 28 vols. (years) each with index. (Typewritten copy in files of Great Smoky Mountains National Park).

• Willner, G.R., G.A. Feldhamer, E.E. Zucker, and J.A. Chapman. 1980. Ondatra zibethicus. Mammalian Species No. 141: 1-8. American Society of Mammalogists.