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Muskrat

Ondatra zibethicus

Muskrats have thick, glossy fur that varies in color from blackish to silvery-brown. (U.S. Fish & Wildlife Service)
Muskrats have thick, glossy fur that varies in color from blackish to silvery-brown. (U.S. Fish & Wildlife Service)

The muskrat is a semi-aquatic mammal with brownish fur and a long, rudder-like tail. It is found in marshes and other shallow-water areas throughout the Chesapeake Bay watershed.

Appearance:

The muskrat has thick, glossy fur that varies in color from blackish to silvery-brown, with a paler throat and belly. Its scaly, hairless, rudder-like tail is flattened on the sides and can grow to 10 inches long. Its small ears are nearly hidden within its fur, and it has partially webbed hind feet. The muskrat grows to a total length of 16 to 24 inches and can weigh up to 4 pounds.

Habitat:

Found mostly in marshes; also lives in other types of wetlands such as swamps and in ponds, lakes, streams and rivers. Prefers shallow areas with 4 to 6 feet of water. Builds dome-shaped lodges of mud and marsh plants on top of tree stumps in shallow water. Lodges can be up to 3 feet tall and have one or more underwater entrances. Will occasionally burrow into stream banks to create a den. Mostly nocturnal, but can sometimes be seen swimming or sunning on a log during the day.

Range:

Found throughout the Chesapeake Bay watershed.

Feeding:

The muskrat feeds mostly on the roots and rhizomes of marsh plants, especially cattails and rushes, but will also eat fish, frogs, insects and shellfish. It consumes about one-third of its weight every day. It will build separate feeding lodges or platforms so it can get out of the water and eat.

Predators:

Muskrats have many predators, including minks, raccoons, owls, hawks, red foxes and bald eagles. Humans hunt muskrats for meat, fur and sport. To hide from predators, they dive underwater or into their lodge.

Reproduction and Life Cycle:

Breeding occurs frequently throughout most of the year. Muskrats nest in chambers inside their lodges. Females have 1 to 3 litters of 5 to 6 young (called kits) each year. Gestation lasts less than one month. Young are born blind. Within 10 days young can swim, and within 21 days they can eat plants. After one month, the female ejects her now-independent young from the lodge. Muskrats can live 3 to 4 years in the wild.

Other Facts:

  • Muskrats are the most common semi-aquatic mammal found in the Bay watershed’s marshes.
  • They are named for the strong musky odor adults emit to communicate with one another. Part of their Latin name, zibethicus, means “musky-odored.”
  • Muskrats have poor vision, hearing and smell.
  • They can be confused with beavers and nutria. Muskrats can be distinguished by their smaller size and their rudder-like tails that are flattened on the sides.
  • To prevent water from getting in its mouth while chewing underwater, they have fur mouth flaps behind their teeth.
  • Muskrats have been observed swimming underwater for up to 17 minutes, surfacing for three seconds, and then going back underwater for another 10 minutes.
  • Snakes, turtles, Canada geese and many other animals use the tops of muskrat lodges as habitat.

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