A muskrat can stay underwater for up to 17 minutes
Like seals and whales, muskrats tolerate a buildup of carbon dioxide better than most mammals, letting them swim submerged for 12 to 17 minutes. They seal their ears against water, paddle with half-webbed hind feet and steer with a scaly, vertically flattened tail found on no other animal.
The common muskrat, Ondatra zibethicus, is a semiaquatic rodent native to North America and introduced to parts of Eurasia and South America. Adults measure 40 to 70 centimetres, half of it tail, and weigh 0.6 to 2 kilograms, roughly four times a brown rat though only slightly longer. It is the sole living species in its genus, the largest of the voles and lemmings in the subfamily Arvicolinae, and far smaller than the beavers it often lives beside. Its nearest relative is the round-tailed muskrat.
A dense two-layer coat, brown to black with a lighter belly and greying with age, keeps out cold water. On land the tail drags behind, leaving easily recognised tracks. Muskrats are mostly active at night and around dawn and dusk, and they follow their own trails through swamps and ponds, even under ice once the surface freezes.
Families consist of a breeding pair and their young, and spring brings fierce disputes over territory and mates. Along streams and lakes they dig bank burrows with underwater entrances 15 to 20 centimetres wide. In marshes they pile vegetation and mud into lodges called push-ups up to 90 centimetres high; in snowy places they plug the openings with fresh plants daily, and floods may sweep the structures away each spring. They also build floating feeding platforms, and their activity keeps patches of marsh open for water birds.
About 95 percent of the diet is plants, especially cattails, with freshwater mussels, frogs, crayfish, fish and small turtles making up the rest. Muskrats store no winter food and sometimes nibble the insides of their own push-ups instead. They may seem to raid beaver stores, yet David Attenborough's series The Life of Mammals filmed what looked like cooperative partnerships between the two. People have long used muskrats for fur and food.
Source: Muskrat
