Recently when I photographed the coots at Baum Lake, I noticed a muskrat house on the shore behind the swimming birds. That muskrat house suggested these two muskrat posts.
Muskrats (Ondatra zibethica) utilize different types of shelter and individual muskrats often have several “homes”.
The most prominent muskrat house is constructed of vegetation at the water’s edge on the shore or in shallow water. It consists of marsh grasses and sedges piled in a conical form that can reach four feet or more in height. Last spring we found one at Ash Creek Wildlife Refuge that was as tall as I am – a couple inches over five feet. In the winter these vegetation piles may be built over an ice hole. The muskrat pushes debris up through the hole forming a dense mass with a cavity big enough for one animal. This provides enough insulation to keep the plunge hole from freezing and the muskrat warm and protected.
Muskrats also build two types of bank burrows with underwater entrances. One is quite complicated with various passages, rooms and a nest chamber. A second type of bank chamber is simply a shallow cavity where the animal can eat and rest. This small cavity is also a place to escape predators.
Finally, although they are not houses, per se, muskrats will also build little platforms of cattail stalks and other vegetation, perhaps mixed with a little mud. These simple platforms can be floating or on the bank and are used as feeding stations and scent posts. The muskrat gets its name from two scent glands near the base of the tail.
With all the burrowing that muskrats do while building their houses, they can cause extensive damage to levees, banks and pond breastworks. Consequently they are often vigorously hunted and trapped in an effort to prevent destruction.
In closing, an interesting anecdote about living with muskrats: A friend built a large pond near his house several years ago. Although the nearest water was about a half mile away, before long he had muskrats living in his pond. Out came the gun and for several years he waged a war with the muskrats in an attempt to keep their numbers down. Not long ago while visiting we noticed a muskrat in the pond and asked about his “war” with the little rodents. Turns out he no longer kills them and lives peacefully with only a couple of muskrats in the pond. When he stopped killing them, the muskrat numbers did not increase. In spite of being prolific breeders, the muskrats self-limit their population in the pond.
The pictures were all taken at Baum Lake. The vegetation house can be seen on the lake bank behind the coots. The other picture shows where the water was disturbed when a muskrat entered its burrow in the bank. Although the two muskrats did not build the sunken log, they were definitely using it as a feeding, sunning and resting station.