Ecology:

Habitat:

Muskrats inhabit marshes and swamps, often reaching high population densities in areas with emergent cattails, and abundant aquatic vegetation. "Houses" are constructed of the same vegetation which composes the muskrat's diet: cattails, burreed, bulrush, etc. When these materials are scarce, a variety of other things may be substituted, including bark, sticks, and additional mud. The houses are about 1.5 m in diameter, with walls that are 30 cm thick. They tend to sit in shallow water with all the vegetation, roots included, conspicuously cleared around them.

Feeding:

Muskrats are mainly herbivorous, but are known to eat mussels, crayfish, and even carrion. In their optimal habitat of rich aquatic vegetation, they eat cattails, burreed, sedges, grasses, loosestrife, water lilies, and so on.

Mortality:

A major cause of mortality in muskrat is trapping, since their pelt is valued highly by the fur industry.

Predators of the muskrat are numerous. Mink predate adult Ondatra by tunnelling into their houses, while raccoons do the same in order to get at the litter. Other frequent predators include fox, coyote, wolves, and dogs. Environmental factors can impact muskrat populations severely. Drought and flooding often kill large numbers of muskrat within small areas. Diseases of Ondatra include internal and external parasites such as worms, fleas and ticks, as well as viral and bacterial illnesses.