Muskrats are good swimmers thanks to their webbed feet and slightly flattened tail. They live around freshwater lakes and rivers with overgrown banks. They dig tunnels into these banks, with the entrance usually located underwater. During the winter, they build lodges from grass and reed. Their diet consists of aquatic plants, grass, plant roots, field crops and occasionally freshwater shells, crustaceans and fish. Muskrats are sometimes consumed by humans. Since muskrats live in water, they are considered equivalent to fish. That is why Catholics living in Detroit are allowed to eat them on days when fish is permitted but not meat.