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This Week’s Creature Feature: The Overlooked Muskrat

They try to avoid us, but their riverbank-busting helps save marshes

      Many times, I have walked along a riverbank and have been startled by both a large animal splashing at my feet and a collapsing shore edge. Muskrats are marsh-dwelling rodents that resemble large, thin gerbils and weigh up to four pounds. When they swim, their long tails swing back and forth in the water like a snake’s. They live in marshes, lakes and streams from Mexico to Northern Canada and are very common in the brackish marshes of the Chesapeake Bay.
       Muskrats try to stay away from humans, unless you are about to step on their home, which they build in a couple of styles. The most common is the push-up or mound. In the open marsh, the rodents collect mud and vegetation and push it together into a mound higher than high tide. The mound is hollow with a below-water entrance.
      The second home, a bank tunnel, is more destructive. At the edge of the water, they sometimes make extensive living chambers by digging out the bank. Unfortunately, banks frequently collapse by their digging. I have stepped into their living room on several occasions. Because the entrance to the tunnel is underwater, the soft earth is hard to see until it caves in.
      The muskrat owners also more closely protect these bank tunnels. They will swim toward you and splash loudly if you get too close, especially when they are protecting offspring. They have one to three broods a year of up to eight kits, so they can quickly overpopulate an area.
      Many animals from turtles to coyotes prey upon muskrats, which helps prevent overpopulation. When there are too many in an area, deadly fights ensue between rival family groups with the loser leaving or dying.
     Muskrats help maintain marshes, while their imported South American cousin, an invasive species called the nutria or coypu, kills marsh grasses by digging up and eating the roots of the plants. They have caused a reduction of Chesapeake marshland and intrusion of deep water. A lot of effort has been made to control nutria, but they are still an issue.