Ondatra zibethicus
PROFILE Muskrat 520x289
The Muskrat is a busy little homebody. It does not migrate, hibernate, or lay up provisions for the winter, like the Beaver or the Pika. It lives alongside rivers and lakes and estuaries in a nest or burrow, venturing out at dusk to gather fresh plant matter to masticate: cattails, water lilies, sometimes the odd frog or crayfish. Often it harvests straight from the murky bottom, staying submerged for up to fifteen minutes at a time to gnaw at stems and roots. Because a Muskrat’s lips seal behind its incisors, it can chew underwater without swallowing a drop.
Muskrats are not actually rats, but cousins to the vole and lemming, their collective 142 species constituting the rodent subfamily Arvicolinae. All are found in the Northern Hemisphere. At twenty inches in length—half of this a vertically compressed, almost hairless tail—and two pounds in weight, the Muskrat is the largest species of its subfamily. The arvicolines have characteristically triangle-tipped molars for chewing roughage, and their teeth grow continuously through life. Arvicolines do not hibernate, even where their range extends up to the Arctic Circle. They are constantly active, seeking out food, tidying their burrows, caring for their copious young. 

Most arvicoline populations exhibit marked patterns of boom and bust, fluctuating cyclically: individuals in a given area reproduce prodigiously until a critical mass is reached; this may take years, representing several rodent generations. Finally, after stretching the limits and resources of their surroundings to an unsustainable extent, the population crashes. Starvation is widespread. Many a Holarctic predator species sees its population graph follow the exact same peaks and troughs of the resident arvicolines.
The Muskrat is a creature adapted to the water. Its hind feet are semi-webbed for swimming, and its flattened tail acts as a paddle, providing additional side-to-side propulsion. Its ears seal shut while submerged. Two layers of soft, supple fur keep the animal warm and dry on its dives to the river bottom for food. In a number of Native American creation myths, the Muskrat dives down to the floor of the primordial sea and returns with mud to construct the earth, succeeding where other animals had failed. So piscine is the Muskrat, in fact, that in Detroit, the Roman Catholic Archdiocese permits the consumption of muskrat on Ash Wednesday, and on the Fridays of Lent, when all meat but fish is prohibited.
And what about its name? It’s probable that “muskrat” comes from the Algonquin word for the creature, muscascus, meaning, literally, “It is red”—a reference to its roan pelage. But the rodents do leave musky scent markings to establish territory—and they do look something like big, drowned rats—so it’s entirely possible that early trappers just called it like they saw (and smelled) it.

Facts About Muskrat

-Found throughout North America in wetland habitat, which it shares with the much-larger Beaver
-In streams, ponds and lakes, will dig burrows into banks; on marshes will construct a heaping nest of vegetation and mud called a "push-up"
-Hind feet are semi-webbed; front feet feature long claws for digging
-Females bear 2-3 litters of small, hairless young per year; litter size ranges from 6-8 pups