Muskrat

An adult muskrat is about 40–70 cm (16–28 in) long, half of that is the tail, and weighs from 0.6–2 kg (1.3–4.4 lb). That is about four times the weight of the brown rat (Rattus norvegicus), though an adult muskrat is only slightly longer, and are almost certainly the largest and heaviest members of the diverse family Cricetidae, which includes all voles, lemmings, and most mice native to the Americas. Muskrats are much smaller than beavers (Castor canadensis), with which they often share their habitat. Muskrats are covered with short, thick fur, which is medium to dark brown or black in color, with the belly a bit lighter (countershaded); as the age increases, it turns a partly gray in color. The fur has two layers, which help protect them from the cold water. They have long tails covered with scales rather than hair, and to aid them in swimming, are slightly flattened vertically, which is a shape that is unique to them. When they walk on land, their tails drag on the ground, which makes their tracks easy to recognize. Muskrats spend most of their time in the water and are well suited for their semiaquatic life. They can swim under water for 12 to 17 minutes. Their bodies, like those of seals and whales, are less sensitive to the buildup of carbon dioxide than those of most other mammals. They can close off their ears to keep the water out. Their hind feet are semiwebbed, although in swimming, their tails are their main means of propulsion.