The muskrat is found in swamps, marshes, and wetlands from northern North America to the Gulf coast and the Mexican border. Early in the 20th century, muskrats were introduced to northern Eurasia. Muskrats are found in wet environments, favoring locations with four to six feet of water. While muskrats are found in ponds, lakes, and swamps, their favorite locations are marshes, where the water level stays constant. Marshes provide the best vegetation for muskrats. They find shelter in bank burrows and their distinctive nests. Bank burrows are tunnels excavated in a bank. The nests of the muskrats are formed by piles of vegetation placed on top of a good base, for example a tree stump, generally in 15 to 40 inches of water.
Muskrats have large, robust bodies, with a total body length of twelve and a half inches. The tail is flat and scaly and is nine and a half inches in length. Muskrats have dense fur that traps air underneath for insulation and buoyancy. Their heads are very large and their ears are almost invisible underneath the fur. The whiskers are medium size. Muskrats have short legs and big feet; the back feet are slightly webbed for swimming. Adult muskrats have glossy upperparts that are dark brown, darker in winter and paler in the summer.
Southern muskrat populations can breed year round while northern populations only breed in the warmer months (March to August). The gestation period is 29 – 30 days and the litter size averages around 6, with northern populations having larger litters. Young are born in a grass lined nest. When born, the muskrat has short dark fur, closed eyes, and weighs around 22 grams. They are able to swim at 10 days and by 21 days can eat green vegetation. In 30 days muskrats gain their independence and will reach adult size in 200 days. Young are cared for and nursed by their mothers in the nest until they are about 2 weeks old, when they begin to swim and eat vegetation.
They are fully weaned by 3 to 4 weeks old and leave their mother’s home range after their first winter, usually when they are less than a year old. Although muskrats have been known to live to 10 years old in captivity, they probably live about 3 years in the wild.
Muskrats are arranged in large family groups and live in definite territories. If the conditions are overcrowded, the females will kick their offspring out of the group. Muskrats continue to live in large groups even when fighting and cannibalism occur in high rates. Muskrats are active at all times of the day but most active from mid-afternoon until just after dusk. Muskrats are good swimmers and can stay underwater for 12 – 17 minutes. Muskrats, however, move relatively slowly on land. Muskrats communicate by musk, which also is used as a warning for intruders.
They are capable of vocalizing by squeaks and squeals. Muskrats have poorly developed senses of sight, hearing, and smell. They are affected by quick changes in temperature, and dry, hot weather is especially bad for them. Their homes and burrows protect them from the elements. Muskrats also have a special adaptation called regional heterothermia, which regulates the flow of blood to the feet and tail, allowing these structures to be cooler than the body core. Muskrats communicate by a secretion from their glands called musk. This scent also serves to warn intruders. They are capable of vocalizing by squeaks and squeals. Muskrats have poorly developed senses of sight, hearing, and smell.
Muskrats are mainly vegetarians but will eat animals as well. Muskrats consume about one-third of their weight every day. Their digestive system is designed for green vegetation. In the summer they eat the roots of aquatic plants. In the winter, they swim under the surface ice to get to the plants. Muskrats also eat agricultural crops. In captivity they should be offered a complete diet of rodent lab blocks, and rat or mouse mix, with bits of fruit or veggies regularly.
Cheerios or wheat bread are great treats, in small quantities. Do NOT feed chocolate, fried foods, salted foods, candy or junk food! They may enjoy crickets and mealworms if they are captive bred, never feed wild insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium during nursing and growth due to demands on their systems at those times, but take care not to overdo it. Water bottles should be used to proved constant, clean water. Ceramic or stoneware food dishes work well for keeping seeds or fresh foods off the floor, and a wire mesh hopper that allows them to eat the lab blocks through without extra waste.