Muskrat

• 1. Introduction

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  The muskrat, Ondatra zibethicus, can stay underwater for 12 to 17 minutes on a single breath. That is longer than most people could hold a conversation without checking their phone. This medium-sized rodent lives in wetlands across North America, where it has long mattered to the people who share its streams and marshes. Native stories place it at the very beginning of the world. Yet the same animal is treated as a pest in parts of Europe, and in some American states its numbers have fallen sharply. How does a creature built like this survive in water and ice? What does it build, and what eats it? And how did one animal become a creation hero, a Lenten meal, a fur coat and a threat to the dikes of low-lying countries?

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• 2. Built For Water

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  An adult muskrat weighs between 0.6 and 2 kg, which is about four times the weight of a brown rat. It is only slightly longer than that rat, though. Body and tail together measure roughly 40 to 70 cm, and the tail makes up about half of that. Among the family Cricetidae, which includes voles, lemmings, most native American mice and Eurasian hamsters, the muskrat is almost certainly the heaviest. Next to a beaver, however, it looks small, and the two often share the same water.

  Its coat is short and thick, running from medium brown to black, with a lighter belly. Two layers of fur keep cold water away from the skin. With age, the fur turns partly gray.

  The tail is the most unusual feature. Scales cover it instead of hair, and it is flattened in a shape found on no other animal. In the water it works as a rudder. On land it drags behind, leaving a trail that makes muskrat tracks easy to recognize. The partly webbed hind feet do most of the pushing.

  The animal's body chemistry matters as much as its shape. Like seals and whales, muskrats tolerate a rising level of carbon dioxide better than most mammals. They can also close off their ears against the water.

  One last detail sits in the tail itself. The musk glands are located there, and they give the animal its scent and, as the next chapters show, much of its name.

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• 3. Houses Of Mud And Reeds

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  Each spring, muskrats fight. They quarrel over territory and over potential mates, and many are injured or killed. Outside those weeks, a household is a male, a female and their young.

  Their homes protect the family from cold and predators. Along streams, ponds and lakes, muskrats dig into the bank and put the entrance underwater, where it is hard to reach. In marshes, they instead heap up vegetation and mud into push-ups, which can rise to 3 ft. Where snow falls, the openings are plugged with plant matter, and the animals replace that plug every day.

  Spring floods sometimes sweep a push-up away. Those lost houses must be rebuilt each year.

  Muskrats also construct feeding platforms. They cut vegetation, support it on a framework of branches and set it afloat. Their work keeps open patches in marshes, and aquatic birds benefit from that open habitat.

  Muskrats are most active at night, at dawn and at dusk. They follow well-worn trails through swamps and ponds. When the water freezes, they keep using those same trails beneath the ice.

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• 4. Eaten And Eating

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  About 95 percent of a muskrat's diet is plant material, chiefly cattails and other aquatic vegetation. The rest is small animals, including freshwater mussels, frogs, crayfish, fish and small turtles. Muskrats do not store food for winter. They sometimes nibble the inside of their own push-ups instead.

  Beavers raise an odd question here. A muskrat may look as if it is stealing from a beaver's food store. Yet the BBC David Attenborough documentary The Life of Mammals shows closer, more cooperative partnerships between the two.

  The list of animals that hunt muskrats is very long. It includes mink, foxes, cougars, coyotes, wolves, lynx, bobcats, raccoons, bears, wolverines, eagles, owls, cottonmouths, American alligators and even bull sharks. Baby muskrats face otters, snapping turtles, herons, bullfrogs, pike, largemouth bass and monitor lizards. In winter, caribou, moose and elk sometimes eat the plants that make up push-ups when other food is scarce.

  The golden jackal is the muskrat's greatest enemy where the animal was introduced in the former Soviet Union. Jackals can wipe muskrats out of shallow waters entirely. In the winter of 1948-49 on the Amu Darya, a river in central Asia, muskrats made up 12.3 percent of jackal droppings. Jackals destroyed 71 percent of muskrat houses, and 16 percent of those then froze and became unusable.

  The jackals also raid the muskrat trade directly. They eat animals caught in traps and take skins that trappers have left out to dry.

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• 5. Boom And Bust

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  A female muskrat can raise two or three litters a year, each with six to eight young. The newborns are hairless and weigh only about 22 g. In southern climates, they mature in six months. In colder northern ones, the wait stretches to about a year.

  That pace of breeding produces dramatic swings. Muskrat numbers climb and then crash on a cycle of six to ten years. Lemmings, close relatives, are famous for the same pattern.

  At the top of a cycle, the effects on a wetland are large. Abundant muskrats can strip away much of the vegetation. They are thought to shape the plant life of prairie wetlands in particular. They choose their favorites, such as cattail and yellow water lily, and so change which plants are common.

  In Florida, muskrats are missing entirely. A different animal, the Florida water rat, fills their place in the ecosystem. Alligators may help explain the absence, since they are an important predator.

  People have shaped the muskrat's fortunes too. Canals and irrigation channels, including the acequias of the southwestern United States, have created new habitat even as natural wetlands vanished. Muskrats can live beside streams carrying sulfurous water from coal mines, where fish and frogs die. They also benefit when people persecute their predators.

  Then came a reversal. According to an April 2024 article in Hakai Magazine, populations have fallen by at least half in 34 US states. In a handful of states, the loss reached 90 to 99 percent. Rhode Island is estimated to hold roughly 15 percent of its former muskrats. The decline began in the 1990s and early 2000s.

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• 6. A Name With Many Roots

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  The word muskrat travelled through several languages before it settled into English. The genus name, Ondatra, comes from ondathra, the Huron word for the animal. It reached Neo-Latin by way of French. The species name zibethicus means musky and is linked to a word for civet musk.

  The common name probably began with an Algonquian word, possibly Powhatan. That word, muscascus, literally means it is red, a reference to the animal's coloring. Another candidate is the Abenaki word mòskwas, which survives in the old English name musquash.

  The smell of the animal, which it uses to mark territory, pushed the name toward musk. Its flattened tail added a comparison to the beaver, so it became musk-beaver. Eventually its resemblance to rats produced the name we use today.

  Biologists classify it as the only living species in its genus. It is the largest member of the subfamily Arvicolinae, which holds 142 other species, mostly voles and lemmings. Sixteen subspecies are recognized, among them O. z. albus, O. z. osoyoosensis and O. z. zibethicus.

  A related Latin tag also appears in a legal list far from any marsh, as the following chapter shows.

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• 7. Invaders Of The Dikes

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  In 1905, five muskrats were released into a park at Dobříš. Two were males and three were females. The House of Colloredo-Mansfeld released them. Europeans had brought the animal over at the start of the 20th century as a source of fur, and its descendants spread across northern Europe and Asia.

  Today, the muskrat is an invasive species in northwestern Europe. Since the 2nd of August 2017, it has appeared on the European Union list of invasive alien species of Union concern. The listing bars anyone in the EU from importing, breeding, transporting, selling or deliberately releasing it.

  The damage is practical. In Belgium, France and the Netherlands, the muskrat is considered a pest. Its burrows weaken the dikes and levees that protect those low-lying countries from flooding. Authorities trap, poison and hunt the animals to hold numbers down. Muskrats also eat corn and other crops grown near water, and they damage flood control systems and river banks across the continent.

  In delicate ecosystems, the concern goes further, because muskrats can outcompete or displace native species. Several European countries run eradication programs.

  Far away, New Zealand takes no chances. Under its Hazardous Substances and New Organisms Act 1996, the muskrat is a prohibited new organism, and nobody may import it.

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• 8. Fur, Friday, And Myth

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  Muskrat fur becomes prime in northern North America at the beginning of December. Trapping grew into an important industry there in the early 20th century. Furriers trimmed and dyed the pelts and sold them widely in the United States as Hudson seal. Today, the winter hats of the Royal Canadian Mounted Police are still made from muskrat fur.

  The animal has also been dinner. Since the 19th century in southeastern Michigan, some Catholics have eaten it. A longstanding dispensation allows muskrat on Fridays, on Ash Wednesday and on the Fridays of Lent, when meat other than fish is forbidden. In 2019, reports described a series of Lenten muskrat dinners along the Detroit River. At a single dinner, up to 900 muskrats were eaten.

  The cook starts by removing the musk glands, which sit in the tail but can taint the lower belly. Then comes gutting and cleaning. The meat is parboiled for four hours with onion and garlic, and finally fried.

  Native Americans have long regarded the muskrat as important. Some watch the size and timing of its lodge building to predict how much snow winter will bring. In several creation myths, the other animals fail to reach the bottom of the primordial sea. The muskrat dives down and returns with the mud from which the earth is made.

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