The nest, or den, is reached by means of a tunnel which usually opens under water. In addition to building homes, muskrats often undertake other construction. Platforms for resting and feeding are made of mud and vegetation, and sometimes jetties are built for landing places along marshy shores. The area an individual occupies depends to a certain extent upon the size and shape of the water area in which it lives. Muskrats living in the center of a marsh usually occupy a circular area, while those living along the shoreline of a marsh or river occupy a narrow area extending from bank burrow out several hundred feet into deep water.
Muskrats readily fight one another, especially during food shortages.
This is one way the muskrat population of an area is kept within the limits of the food supply. In the marshy areas of Missouri,muskrats eat rootstocks and stems of cattail and three-square bulrush, and the seeds of lotus. In other areas of the state, white clover, corn and bluegrass are preferred foods. Muskrats living along Ozark streams feed upon freshwater clams, snails, crayfish, fish, frogs and aquatic plants. The breeding season in Missouri begins in late winter and extends to the middle of September.