Muskrat, photo by Adore707.

The University of Michigan Animal Diversity Web entry for Ondatra zibethicus, muskrat says:

Muskrats are found in wet environments, favoring locations with four to six feet of water. While muskrats are found in ponds, lakes, and swamps, their favorite locations are marshes, where the water level stays constant. Marshes provide the best vegetation for muskrats. They find shelter in bank burrows and their distinctive nests. Bank burrows are tunnels excavated in a bank. The nests of the muskrats are formed by piles of vegetation placed on top of a good base, for example a tree stump, generally in 15 to 40 inches of water.

…Muskrats have large, robust bodies, with a total body length of twelve and a half inches. The tail is flat and scaly and is nine and a half inches in length. Muskrats have dense fur that traps air underneath for insulation and buoyancy. Their heads are very large and their ears are almost invisible underneath the fur. The whiskers are mediun size. Muskrats have short legs and big feet; the back feet are slightly webbed for swimming. Adult muskrats have glossy upper parts that are dark brown, darker in winter and paler in the summer.

A Michigan muskrat recently made the news in these photos from the Kalamazoo River oil spill.

See this photo bigger in Eli’s Nature slideshow and check out more Michigan animals on Michigan in Pictures.