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Muskrats (Ondatra zibethicus) resemble large field mice with none of the offensive traits or habits of the common rat. They weigh about 3 pounds, have bead like eyes, and their ears are nearly concealed in dense fur. The hind feet are quite large, and while not webbed, have stiff hair between the toes, which aid in swimming. The tail is flattened on the sides and serves as a rudder. Most muskrats have long, dark, reddish-brown fur on the upper parts of the body and short, silver-tipped fur underneath. Guard hairs are long and durable while the underfur is fine, soft and waterproof. This mammal is well equipped for its aquatic habitat but is awkward on land.
Muskrats are vegetarians, but if unable to secure plant foods, they will feed on carcasses of fish, frogs, and other muskrats. Nearly all plants growing in and near their water areas are eaten, but cattails are the backbone of their diet. Food is not stored for winter use, so they must dig roots and tubers from beneath the ice, returning to their house and burrow to feed. If food sources are too far from the house, a feeding shelter called a “push-up” is built on the ice. A similar feeding platform – a raft consisting of discarded plant food – is constructed for summer use. A dense winter population feeding on roots and bulbs in a marsh or small lake may consume nearly all the roots. Upper parts decay the following spring, turning the water and soil sour so that few plants will grow in that area. This is called an eat-out, and if little water moves through it, this portion of the marsh may be unproductive for several years.
Distribution and Abundance
Muskrats occur throughout Indiana but are most numerous in areas of abundant shallow water. The northeastern section of the state produces a substantial proportion of these rodents each year. The construction of private ponds for livestock watering or recreation across Indiana has been important in offsetting the losses of muskrat habitat due to wetland drainage and stream channelization. Muskrats living along streams prefer to place nest chambers above the water level in burrows entered from the water. In marshes and lakes, they use cattails and other aquatic plants to construct houses resembling small haystacks.
Courtship is conducted by the female as she swims about singing her love song resembling the squeak of a mouse. Two or three litters may be produced each year, but most muskrats in Indiana are born in May and June, 28 to 30 days after mating. Litters averaging about six in size are born in a shredded cattail or grass nest. The male assists in preparing the chamber but does not enter the house or burrow after the young are born. Kits are naked, blind and helpless at birth, but are weaned at 4 weeks of age. At this time, they can swim but do not dive well. If the mother is to have another litter soon, they are driven from the house or burrow, but the last litter of the season often spends the winter with its parents. Muskrats are quite tolerant of each other, and except during the breeding season, several may live together. Many muskrats spend their entire lives within a few hundred yards of their birthplace, but in autumn and spring, some are forced to migrate to less-crowded areas and may wander several miles to establish new homes.
Prevention and Control
Resident landowners and tenants can trap or shoot a muskrat that is causing damage on their own property. The muskrat must be euthanized or released within the county of capture on property in which you have permission. In order to prevent the spread of disease, the DNR encourages homeowners to safely and humanely euthanize the muskrats, if possible. If you do not want to trap the muskrat yourself, contact a licensed nuisance wild animal control operator.
Muskrats can sometimes be prevented from digging in a pond dam or bank by rip-rapping. Drawing the pond down at least 2 feet below normal water levels during the winter can also encourage them to leave. Once it is drawn-down, you can trap or shoot (where legal) the muskrat, then fill the dens, burrows and runs and rip-rap the dam with stone.
Make a concentrated effort to reduce the breeding population of muskrats during the winter months through either trapping or shooting (where legal).