a muskrat's winter home
From St. Nicholas magazine, October 1938:

When late autumn comes, you are likely to see the dome-shaped houses of the muskrat down along the marsh or in a shallow pond or creek. Often there are several of them in a group, for muskrats tend to be sociable.

Strangely enough, a muskrat builds its winter lodging out of the food it likes best to eat. Grasses, rushes, and the stems and leaves of water plants are gathered and placed on the bottom of the pond or slow-moving stream as a foundation. Then, without any special arrangement, more plants are heaped on the first ones and plastered with mud until the house becomes a dome-shaped structure, rising sometimes two or three feet above the water.

The part of the house above the water is hollowed out for a living-room, and from this room one or more tunnels lead down through the stems, roots, and leaves into the water below the point where the water would freeze. This is so that the owners will not be ice-bound, for the part of the house above the water usually has no openings except perhaps an airhole or two.

Muskrats build their dome-shaped winter homes only where shores are flat. Where shores are high, they burrow into the banks and use these snug underground hiding-places as both winter and summer homes.

The muskrat's winter lodge made of plants is much like the one constructed by the beaver except that it is smaller and not so strongly built.
- posted by pioneergirl at 1:34 AM