Hands-down, the favorite TV show for kids growing up in a previous era was The Mickey Mouse Club. The spell those creatures with big ears cast over children continues to this day, now as the cartoon characters draw masses of children to the vast Disney empire. But what if Uncle Walt had had a different inspiration? What if while passing by a clear-running stream on his morning walk or stopping near a patch of cattails bordering a pond, he spotted a cartoon-like rodent from real life, with a pointy nose and whiskers, webbed feet, and a long tail? Would we be watching reruns of The Mickey Muskrat Club?
We’ll never know why Walt Disney chose such an ignominious rodent as the mouse to elevate to global icon status when perfectly lovable large rodents with outsized personalities went unclaimed—marmots, prairie dogs, beaver, capybaras, or even porcupines. But let’s fantasize for a moment that cartoon editors presented Walt Disney with sketches of our local muskrat, and it had won the charm contest.
There is much to be said for this semi-aquatic mammal, Disney might be told. Living alongside beavers that also prefer marshy habitats, it can readily be distinguished from the latter by its smaller size and its distinctive narrow, long tail whereas the beaver has a broad flat tail; both use this appendage like a rudder. To swim, both use their powerful hind webbed feet. Muskrats can stay under for a long time, too, as much as 17 minutes similar to the beaver. Their bodies, like marine mammals, can tolerate the build-up of CO2 and lactic acid in the muscles.
Muskrats run only about 16-28 inches long, with half that length being their whip-like tail so about half as long as beavers. They are much lighter, too: beavers can reach 60 lbs. while muskrats only weigh between 1.4 and 4.4 lbs. Even so, muskrats are the largest member of the family of rodents known as the Cricetidae which includes deer mice, lemmings, hamsters, and voles (but not true rats which are part of the Muridae family; beavers belong to the family Castoridae in the Order Rodentia).
Muskrats have reddish brown fur, attractive enough that a fur industry developed around this species. For a time muskrat lined coats were in fashion. Muskrats may look cute, but be careful, inside that body is a musk gland, from which the animal’s name came, that can stink up a place. The scientific name is Ondatra zibethica; Ondatra being the Huron word for this species, and the specific epithet, zibethica, refers to the word civet or civet musk, another species with scent glands. Muskrats, like the mustelids such as skunks, wolverines, and weasels, use their special glands to scent-mark their territories.
If you are trying to spot a muskrat in the Potomac, watch the river and look for a v-shaped chevron with a nose at the tip of the arrow, making its way across to Virginia or back, especially around dawn or dusk. Another way to find them is to look for their dens. The muskrat abode has a charming name, just like its inhabitants—the dwelling is called a “push-up” because the shelter, constructed of sticks and other material, looks like a forest igloo. The entrance to the push-up is from underwater, giving the muskrat some privacy and serving as a safety feature from predators. Lots of creatures will eat muskrats, especially baby muskrats. The long list includes most North American carnivorous mammals and birds, snakes, reptiles, and even large fish.
Another good place to find muskrats is in a wetland or in part of the canal that is rich in cattails—one of their favorite food items. Muskrats live mostly on vegetable matter, but like most mammals, they are opportunists, occasionally dining on small animals. Like beavers, they can heavily influence local vegetation composition and structure by their selective feeding.
Muskrats are native to only North America, but were introduced widely in Europe in the 20th century for reasons unknown, perhaps to encourage economic use of another fur-bearing mammal for the fashion industry. They have taken root in northern Europe where they are considered a pest species, but attempts to eradicate them have proved difficult.
I was not yet a biologist when I was first introduced to Mickey and Minnie, but now it occurs to me that Walt must have kept them on contraceptives as part of their contract: they never had offspring during their Disney run. It’s hard to restrain libidinous muskrats who can have two to three litters per year with six to eight muskrateers per litter. Most rodents, except for prairie dogs and a few others are prolific breeders. It’s part of what is called their life-history strategy—life spans are short, in the case of the muskrat of about 3-4 years, so pump out the young while you can to pass as many genes as possible into the next generation. Reports of muskrats surviving to 10 years exist, but most are probably taken by predators before they reach the golden years. The population of muskrats in our area seems stable, so long after Mickey and Minnie are gone, there will be muskrats chewing on a cattail or gathering sticks and reeds for a new push-up, preparing to house the next generation of pups.
By Eric Dinerstein
Illustration by Trudy Nicholson