Muskrat
Ondatra zibethicus

Appearance

The muskrat has thick, glossy fur that varies in color from blackish to silvery-brown. They have a paler colored throat and belly. Its scaly, hairless, rudder-like tail is flattened on the sides and can grow to 10 inches long. It has small ears which are almost 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.

Feeding

The muskrat feeds mostly on the roots and rhizomes of marsh plants, especially cattails and rushes. They will also eat fish, frogs, insects and shellfish. A muskrat will eat 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.

Voice

Vocalizations such as “chirping”, and “whining” function as signals. Muskrats sometimes slap their tail on the water, possibly to alert neighbors of impending danger.

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 independent young leave the lodge. Muskrats can live 3 to 4 years in the wild.

Did You Know?

• 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 prefer shallow areas with 4 to 6 feet of water. They build 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. They are mostly nocturnal, but can sometimes be seen swimming or sunning on a log during the day.
• 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.

Sources and Additional Information

• Chesapeake Bay: Nature of the Estuary, A Field Guide by Christopher P. White
• Wildlife Information: Common Muskrat – Virginia Department of Wildlife Resources
• Animal Diversity Web: Ondatra zibethicus – University of Michigan Museum of Zoology
• Ondatra zibethicus – U.S. Forest Service