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MuskratMuskrat

Ondatra zibethicus

By Tom Dickson. Photo by Alan G. Nelson

Early one evening while fishing, you see a rabbit-sized animal swimming low in the water near shore. Is it an otter? A beaver?
Most likely the creature is a muskrat, a common furbearing mammal found throughout Montana that is most active when the sun is down.

Named for the smelly fluid secreted by two glands on its lower stomach, the muskrat is a medium-sized rodent closely related to the vole. Most active at night, it is found along rivers and streams and in lakes, reservoirs, ponds, and marshes in the countryside as well as in towns and cities.

Identification
Muskrats are from 18 to 24 inches long (including the tail) and weigh 2 to 5 pounds. They have small ears and eyes and often sit hunched over. Muskrats look somewhat like a beaver, though beavers are much larger (25 to 75 pounds). Also, beavers have a wide, flat tail, while the muskrat’s tail, though also scaled and hairless, is thinner and flattened laterally, like a boat rudder.

Muskrats have small front feet, used mainly to hold food, but their hind feet are large and webbed. These act as paddles, propelling the muskrat through the water as it steers with its strong tail.

Muskrats are chocolate brown on the back, fading to light brown with a reddish tinge on the sides. The belly and throat are cream-colored.

Fur
Muskrats, which have a soft fur used for coats and hats, are the most commonly trapped animal in North America. The underfur next to the muskrat’s body traps air and prevents its skin from getting wet. Long brown guard hairs cover and protect the underfur.

Predators
Because muskrats move awkwardly on land, they can be easy prey for coyotes, foxes, lynxes, and raptors. But in the water, where they spend most of their time, these excellent swimmers can escape most any predators except mink and otters.

Lodging
Muskrats live almost anywhere there is water. In slow-moving rivers, they burrow into banks from underwater, angling their tunnels up so the dry living chambers are above water level.

In lakes and marshes, muskrats build dome-shaped houses of cut bulrushes, cattails, and mud. Muskrat lodges, which look like those of beavers only smaller, are usually 6 to 8 feet in diameter at the base and have walls 1 to 2 feet thick. Muskrats enter their lodges, which contain several different sleeping areas, from underwater.

Feeding
Like bears, humans, and many other animals, muskrats are omnivores. They eat the roots, stems, leaves, and fruits of many water plants, such as cattails, water lilies, and rushes, but will also consume small fish, freshwater clams, snails, and even turtles.

Near their lodges, muskrats build several small feeding mounds, called “push-ups,” where they can sit and eat undisturbed by predators.

Reproduction
You’ve heard the term “breed like rabbits”? How about “breed like muskrats”? An adult female can have two or three litters of up to ten young each summer, and some have been known to produce as many as 45 kits in a single year.

The kits, which are naked, blind, and nearly helpless, weigh about one-half ounce at birth. But they grow rapidly. Within two weeks they can swim and dive, and after just one month they can live on their own.

Population
Muskrat numbers have increased in parts of Montana over the years due to the construction of artificial wetlands, but numbers have declined where natural wetlands have been drained. If you haven’t seen many muskrats recently, you’re not alone. Brian Giddings, FWP’s furbearer coordinator, says the state’s trapping harvest has been down the past several years, likely due to drought. The rain shortage has dried up many marshes and ponds, giving muskrats fewer places to live.

“ Once conditions improve, muskrats will likely return to those areas,” Giddings says.

When the rains return, watch out. Muskrats are so prolific they can quickly overpopulate a marsh. In what is dubbed an “eat-out,” muskrats consume all the cattails and bulrushes in an area. Then the starving animals turn on each other, fighting to the death and even eating their young. This gruesome behavior keeps their numbers in proportion to the food supply.

Fun Facts
Muskrats and beavers are the only mammals that build their home in the water. Unlike the beaver, however, the muskrat does not store food for the winter. It needs to eat fresh plants each day, and sometimes it makes channels in the mud to get from its house to reach food under the ice. To stay warm in winter, groups of muskrats huddle together in their lodge.Bear bullet

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