Muskrat
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.
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