Episode 39
Copyright © John Page Williams, Jr. all rights reserved.
This is John Page Williams with another reading from Chesapeake Almanac. The month is December and this one is entitled, "Muskrats and Winter Marshes."
My daughter Kelly and her friend Stacey were rowing a small boat around a salt pond on the Severn above Annapolis one summer day. Kelly noticed some sprigs of cordgrass floating on the surface near a pocket marsh. "Look," she said, "A muskrat has been here." "Huh?" said Stacey. "How do you know?" "See," said Kelly, "They've all been bitten off." Sure enough, each stalk had been cut at a 45-degree angle near the base. "You mean they eat grass?" asked Stacey. "That's weird." "It is not. Haven't you ever chewed a grass stem?" queried Kelly. She rowed over to the marsh, pulled several stems of grass out from their bases, and peeled them down to the tender parts. Stacey screwed up her courage and took a bite. "Hey, that's good," she said. "It tastes like celery, but salty and sweet at the same time. Maybe muskrats aren't so weird after all."
Muskrats are the Chesapeake's most abundant aquatic animals. The species breaks down into 16 subspecies that range over most of North America. The animals are rodents, related to moles, mice, beavers, and squirrels. Muskrats measure 10 to 16 inches long with five to six inches of scaly, nearly hairless tail. Weight for adults in the Bay is two to three pounds, with males being slightly heavier than females. The animal's coat color generally ranges from rusty red-brown to nearly black, though several color mutations are known. Soft, dense fur grows under long, glossy guard hairs. Muskrats swim well, chugging across the surface by kicking their webbed hind feet and diving when necessary to feed or to avoid danger. In general, they're most active at night.
At the front of a muskrat's upper and lower jaws are paired, sharp incisor teeth, hence the neat cuts on Kelly's and Stacey's cordgrass sprigs. There are rows of molars behind for chewing plant food thoroughly. The animals primarily eat the tender parts of submerged vegetation and marsh plants. In the Chesapeake region, their major foods are narrowleaf cattail in freshwater marshes and a bulrush, Olney threesquare, in brackish marshes. As noted by Kelly and Stacey, they also eat a good deal of saltmarsh cordgrass. Locally, this diet opens up hundreds of thousands of marshland acres to muskrats, especially the broad threesquare marshes of Dorchester County below Cambridge on the Eastern Shore. In addition, the large meander curves on major rivers offer brackish marshes with communities of cattails, bulrushes, and cordgrasses growing side by side.
With so much food available, muskrats are highly prolific. They produce litters through most of the year, though the peak period is March to September. Females bear two to five young per litter and can produce three litters a year. Kid mortality is high. Over half of a litter may die in the first year from disease or predation. Adult mortality is high too. Predators include marsh hawks, raccoons, foxes, and man. Maximum life span in the wild appears to be four years, but the average is one or two. Muskrats grow fast, breed fast, and die fast.
It's easy to get a feel for the muskrat's life-style in warm weather. Kelly and Stacey were exploring Ray's Pond in August, and the cordgrass was still green and growing. Now it's winter: the grass is dead, at least aboveground; the water is very cold; and the marshes are iced over part of the time. Muskrats are especially interesting now because they're one of the few species on the Bay that are active in winter.
Their major strategy for cold weather is to build shelters. On the rivers and creeks, some muskrats dig burrows into the banks. On the open marshes, they build lodges. These are four to six feet in diameter and two to three feet high, usually rounded or oval, with one or two chambers inside and a couple of exits to leads cut through the marsh. Materials come from whatever plants are readily available, and the lodges are reasonably well insulated. Often the system of short leads will connect the lodge with several feed huts, smaller and simpler shelters close to food supplies where a muskrat can get out of the weather to eat.
Winter food foraging on the Bay requires a change in behavior because there are no tender shoots to eat. Instead, the muskrats concentrate on digging into the marsh peat for the starchy rootstocks of cattails and bulrushes. A very hard freeze can make digging difficult, so the animals will dive below whatever ice is present and burrow into marsh banks from the side to find food. Finally, if necessary, they'll switch to animal foods like clams, grass shrimp, and killifish.
Shelter building and resourceful ways of feeding are important behavioral strategies. Muskrats also have a physiological one: their coats grow denser and glossier in the winter, increasing their insulating and water-repellent qualities. While it is possible for a muskrat to stay in the water too long and get wet through to the skin, the animal usually avoids this situation by using its shelter and lead system to minimize exposure.
For us, it's difficult to understand how a warm-blooded mammal can live in an aquatic environment in the dead of winter. The lessons are clear—the food value in the stalk hearts and rootstocks of marsh plants is remarkably high; the huts provide snug housing; and muskrat fur is a very efficient insulation system. There's plenty to admire in this little rodent.
For more happenings around the Bay in December see our other Chesapeake Almanac podcasts and read our blog posts "Buffleheads and a Winter Miracle" and "Getting Outside in December."
