Life History and Reproduction:
Mom, where do babies come from?

     Even as pups, young muskrats have a lot to worry about. Muskrats are known to transfer their young, helpless pups on top of lodges, nests, and even inside of other unused lodges and just leave them there to fend for themselves or simply just kill their young themselves. This irresponsible behavior doesn’t even seem to bother or affect the careless mother, and if just a few of her pups manage to survive long enough to take care of themselves it’s fine with her. Mother muskrats that are still taking care of their pups become very hostile towards other young muskrats. Although they may let young muskrats near their nests, most often the female muskrats will become very territorial and attack any young muskrat that comes near her lodge and nest. While muskrats are not readily willing to protect their young from other muskrats or threats, they will do anything to protect themselves. They will not only attack young muskrats that have emigrated from another habitat, but will also attack young that were born in their same habitat or even their previous offspring.

     It is not unusual for muskrats to live with each other during winter months within a certain territory when the breeding season has slowed down significantly. Typically a “family” will consist of a male, a female, and their pups that haven’t matured enough to have made their own lodge and fend for themselves. In this situation, breeding does not occur until the spring when there is more room and more resources to raise new pups. If the habitat is at its maximum carrying capacity or very close, young muskrats often don’t have any other choice but to travel to another nearby habitat. Muskrats however do not like to travel on land for very far distances because of the higher risk of being injured or killed by predators such as mink, fox, raccoons, owls, hawks, snapping turtles, and snakes. Most muskrats, if forced to travel away from their birthplace, will only migrate a few miles at the most to find a new suitable habitat to live in.

     Muskrats reproduce several times a year at and also at a rather quick rate that is commonly associated with the Order Rodentia (see Classification). However, muskrats do not produce at a steady rate all year long; they have a breeding season that is relatively similar within all types of muskrats. This breeding season starts during the late winter months, usually in February, as the cold winter months slowly start to change into spring. The season continues for about six to seven months and usually slows down in September as the temperatures start to drop and ice forms in the muskrats' habitat. Most female muskrats that are able to reproduce will have one last litter during the winter and take care of the pups until she is ready to reproduce again the following spring.

     In observations conducted by J. Sather in 1958, the data he collected showed that there were 3 times during the breeding season where the birth rates were at their highest (Sather, 1958). These times were in early May, June, and late August continuing into early September. Sather also found that the average number of pups per litter were different throughout the breeding season. During the beginning of the breeding season in the spring and summer, breeding females averaged six to seven pups per litter. Also, during the winter when breeding is much slower, breeding females averaged only four to five pups per litter.

     Muskrats typically start breeding at about a year of age during the spring after their birth. The method muskrats use to find a mate is opposite from what is usually seen in other mammals. Usually, the males are the ones to show themselves off to attract females, but with muskrats females search for and try to attract males by swimming around and “singing” a love song by squeaking. Muskrats are mostly monogamous organisms and therefore stay with their partner during the breeding season.

    


     Muskrats, like other rodents, have a relatively short gestation period. Thanks to this short gestation period, muskrats are able to have up to seven or eight litters per year with as many as three to eight pups per litter. While this many litters and pups is not ideal, it is very possible, especially when the muskrat’s nutritional and habitat requirements are met. Female muskrats usually give birth to their pups in a den or in a nest made of grasses, reeds, and other materials abundant in their habitat. Male muskrats commonly help their mate to build the lodge that their young will be raised in; however the males usually will not stay in it once the pups are born.

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