It had been a while since I had driven down the road that passes beside a large marsh west of here. In the summer, it is dense with cattails. It’s hard to see past the line of cattails lining the road. But now, the weight of the snow and the breaking down of the cattails has revealed…Muskratville!
The snow piled on domed roofs catches the eye and dozens of muskrat abodes have suddenly (it seems) been made visible. Muskrats (Ondatra zibethicus) build a couple of kinds of structures, lodges and pushups. Pushups are smaller than lodges and serve as resting places where muskrats can eat in safety.
Muskrats forage underwater for roots and underground stems of plants such as pondweed, water milfoil, and burr-reed. Using a line of pushups stretching away from its lodge, a muskrat can gather food farther away form its lodge than it could otherwise reach. As well as providing a feeding station, pushups also provide an insulated shelter out of the icy water that can quickly rob heat from the muskrat’s naked tail and feet.
Pushups are created in autumn, when the pond first freezes over. The muskrat chews a hole through the thin ice, often around an air bubble or a spot where marsh gas is escaping. Then the muskrat pushes up a pile of fine roots, submerged vegetation, and other debris to form a dome. As the pile grows, it forms an enclosed cavity on the ice surface.
The muskrat visits the pushup throughout the winter to keep the ice open. Pushups are generally constructed in straight lines, about 12 yards apart, in line with a favoured feeding ground. I’m not sure which of these structures might be lodges, and which might be pushups, but the many structures certainly suggest an active community.
For more on muskrats, see my November 17th post, Busy as a Beaver. You can also learn more at The Marvelous in Nature at Muskrat in our Meadow, and see another muskrat push-up at Back on the Blades.
Willow House Chronicles 