information:extraction
Behavior

Muskrats normally live in families consisting of a male and female and their young. During the spring, they often fight with other muskrats over territory and potential mates. Many are injured or killed in these fights. Muskrat families build nests to protect themselves and their young from cold and predators. Muskrats burrow into the bank with an underwater entrance in streams, ponds, or lakes. These entrances are 15–20 cm (6–8 in) wide. In marshes, push-ups are constructed from vegetation and mud. These push-ups are up to 90 cm (3 ft) in height. In snowy areas, they keep the openings to their push-ups closed by plugging them with vegetation, which they replace daily. Some muskrat push-ups are swept away in spring floods and must be replaced yearly. Muskrats also build feeding platforms constructed in the water from cut pieces of vegetation supported by a branch structure. They help maintain open areas in marshes, which helps to provide habitat for aquatic birds.

Muskrats are most active at night or near dawn and dusk. They feed on cattails and other aquatic vegetation. They do not store food for the winter, but sometimes eat the insides of their push-ups. While they may appear to steal food beavers have stored, more seemingly cooperative partnerships with beavers exist, as featured in the BBC David Attenborough wildlife documentary The Life of Mammals. Plant materials compose about 95% of their diets, but they also eat small animals, such as freshwater mussels, frogs, crayfish, fish, and small turtles. Muskrats follow trails they make in swamps and ponds. They continue to follow their trails under the ice when the water freezes.

Muskrats provide an important food resource for many other animals, including mink, foxes, cougars, coyotes, wolves, lynx, bobcats, raccoons, bears, wolverines, eagles, hawks, large owls, snakes, alligators, and bull sharks. Otters, snapping turtles, herons, bullfrogs, large fish such as pike and largemouth bass, and predatory land reptiles such as monitor lizards prey on baby muskrats. Caribou, moose, and elk sometimes feed on the vegetation which makes up muskrat push-ups during the winter when other food is scarce for them. In their introduced range in the former Soviet Union, the muskrat's greatest predator is the golden jackal. They can be completely eradicated in shallow water bodies. During the winter of 1948–49 in the Amu Darya (river in central Asia), muskrats constituted 12.3% of jackal feces contents, and 71% of muskrat houses were destroyed by jackals, 16% of which froze and became unsuitable for muskrat occupation. Jackals also harm the muskrat industry by eating muskrats caught in traps or taking skins left out to dry.

Muskrats, like most rodents, are prolific breeders. Females can have two or three litters a year of six to eight young each. The babies are born small and hairless and weigh only about 22 g (340 gr). In southern environments, young muskrats mature in six months, while in colder northern environments, it takes about a year. Muskrat populations appear to go through a regular pattern of rise and dramatic decline spread over a six- to 10-year period. Some other rodents, including famously the muskrat's close relatives, such as the lemmings, go through the same type of population changes.