The muskrat (Ondatra zibethicus) is a common semi-aquatic rodent found across North America, inhabiting a wide variety of wetland environments. While often mistaken for other aquatic rodents, muskrats possess distinct characteristics that allow them to thrive in their watery habitats.
Physical Traits and Identification
Muskrats are medium-sized rodents, typically measuring between 16 to 25 inches in total length, with about half of that length attributed to their tail. Adults generally weigh between 2 to 5 pounds, making them considerably smaller than beavers but larger than common rats. Their fur is dense and waterproof, ranging in color from medium to dark brown on the upper body and a lighter grayish-brown or silvery shade on the belly. This two-layered coat provides insulation against cold water.
A distinguishing feature is its long, scaly, almost hairless tail, which is vertically flattened unlike a beaver’s broad, flat tail, aiding in propulsion and steering. Their small eyes and tiny, barely visible ears are suited for their semi-aquatic life. Muskrats possess partially webbed hind feet, their primary means of propulsion when swimming, while smaller front feet are adapted for digging. These traits differentiate them from beavers, which are much larger with a paddle-like tail, and nutria, which have a rounder tail.
Where Muskrats Live and How They Behave
Muskrats prefer freshwater wetlands, including marshes, ponds, slow-moving rivers, and streams, where abundant aquatic vegetation is available. Muskrats are excellent swimmers and can remain submerged for extended periods, typically 12 to 17 minutes, by closing their ears to keep water out. Their webbed hind feet and vertically flattened tail allow them to swim efficiently, even backwards.
These rodents construct two main types of homes: lodges or burrows. In shallow water with ample vegetation, they build dome-shaped “lodges” from mud and plant materials, resembling smaller versions of beaver lodges. These lodges can be up to 3 feet tall and have underwater entrances, leading to dry living chambers above water level. Alternatively, in areas with steep banks, muskrats will burrow into the soil, creating dens with underwater entrances and dry chambers.
Muskrats are generally nocturnal or crepuscular, meaning they are most active during dawn and dusk, though they can be observed during the day. They are territorial, especially during breeding season, but several muskrats may share a den in winter to conserve heat.
What Muskrats Eat and Their Environmental Impact
Muskrats are primarily herbivorous, with aquatic vegetation forming the bulk of their diet. They consume various parts of plants, including roots, stems, leaves, and fruits, with a particular fondness for cattails, water lilies, sedges, and rushes. They use their sharp incisors and forefeet to harvest these plants. While their diet is about 95% plant-based, muskrats may occasionally supplement it with small amounts of animal matter such as mussels, crayfish, snails, frogs, or small fish, especially when plant food is scarce.
The feeding and building activities of muskrats have a notable impact on their environment. Their consumption of dense aquatic vegetation, particularly invasive species like hybrid cattails, can create open water channels, often referred to as “eat-outs.” These clearings can benefit other wetland species by increasing biodiversity and creating patchy ecosystems. However, their burrowing habits can also cause damage to human infrastructure, such as dikes, dams, and levees, potentially leading to leaks or structural weakening. Muskrats may also forage on agricultural crops if they are located near water sources.