Muskrat

Ondatra zibethicus

The muskrat is an aquatic rodent with thick, glossy fur that varies in color from blackish to rich, silvery brown. Adults have:

• A scaly, black, rudder-like tail that is flattened on the sides and grows to about 10 inches long.
• Partially webbed hind feet.

Muskrats grow to a total length of about 16 to 24 inches and can weigh up to 4 pounds.

Where does the muskrat live?

Muskrats are found in watery habitats throughout the Bay watershed, including ponds, swamps, lakes, streams, rivers, marshes and wetlands. They will occasionally burrow into stream banks to create a den.

Muskrats are mostly nocturnal, but can also often be seen swimming or sunning themselves on logs during the day.

What does the muskrat eat?

Muskrats feed mostly on the rhizomes of marsh plants, but will also eat fish, frogs, insects and shellfish. They eat privately on feeding platforms, which they construct from marsh plants.

When does the muskrat breed?

Muskrats breed frequently throughout most the year.

• Muskrats build dome-shaped lodges of mud and marsh vegetation in shallow water. The lodges can be up to 3 feet tall and have one or more underwater entrances. Inside the lodges are nesting chambers. Each muskrat family lives in its own lodge.
• Female muskrats have one to three litters of five to six young (called kits) per breeding season. The gestation period lasts less than a month.
• Young muskrats are born naked and blind, but grow fur within two weeks.
• After one month, the female muskrat ejects her now-independent young from the nest.

Other facts about the muskrat:

• Muskrats are the most common aquatic mammal found in Bay marshes.
• Ondatra is the Iroquois name for the muskrat, and zibethicus means "musky-odored" in Latin, referring to the scent that breeding males emit.
• Muskrats can be confused with nutria, an invasive aquatic rodent. You can identify a muskrat by its smaller size and long, hairless, laterally flattened tail.
• Muskrats have fur mouth flaps behind their teeth, which seal off their mouth opening and prevent water from getting in their mouths while they are chewing underwater.
• Muskrats have an extraordinary lung capacity; individuals have been seen swimming underwater for up to 17 minutes, surfacing for three seconds, then going back under for another 10 minutes without a breath.