Muskrats are medium-sized mammals seen swimming in North American wetlands. They are indeed rodents, closely related to voles and lemmings. These semi-aquatic creatures inhabit marshes, ponds, and slow-moving streams across the continent. Muskrats are common from the Arctic Circle down to the Gulf of Mexico, adapting their lives entirely around the water environment.
Yes, Muskrats Are Rodents
The muskrat’s placement within the Order Rodentia is determined by anatomical features. All rodents possess a single pair of continuously growing incisors in both the upper and lower jaw. These four teeth are self-sharpening, maintaining a chisel-like edge necessary for gnawing. A large gap, called a diastema, separates these incisors from the grinding cheek teeth.
Muskrats belong to the Family Cricetidae, which includes voles, lemmings, and New World rats and mice. This dental arrangement separates them from groups like rabbits. Muskrats can close their lips behind the incisors, an adaptation that enables them to chew submerged plant material without swallowing water.
Unique Aquatic Adaptations
The physical traits of the muskrat distinguish it from its terrestrial rodent relatives. The most notable adaptation is the tail, which is long, nearly hairless, and laterally flattened like a rudder. This shape is used for steering and propulsion underwater. The hind feet are partially webbed, acting as the primary source of thrust for swimming.
Dense, two-layered fur provides insulation and buoyancy in cold water. The underfur is short and thick, trapping a layer of air, while longer guard hairs repel water. Muskrats can hold their breath for extended periods, typically between 12 and 17 minutes. Like other diving mammals, their system is less sensitive to the buildup of carbon dioxide. Their small ears and nostrils automatically close upon submerging.
Ecological Role and Distribution
Muskrats are native to North America, but they have been introduced in parts of Eurasia and South America. They thrive in freshwater and brackish habitats, favoring areas with abundant aquatic vegetation and still or slow-moving water. The animals construct two main types of shelter: lodges and dens.
In open marshes, muskrats build dome-shaped lodges from piled vegetation and mud that can rise several feet above the water line. If the habitat features stable banks, they excavate bank dens with multiple chambers and underwater entrances. These structures provide protection from weather and predators like mink and owls.
The muskrat is primarily herbivorous, with its diet consisting mainly of aquatic plants such as cattails, reeds, and water lilies. By consuming large quantities of vegetation, muskrats function as significant ecosystem engineers in marsh environments. Their feeding and construction activities create open water channels and clearings, which benefit numerous species of waterfowl and other aquatic life.