THE MUSKRAT 99 



half to three feet above the water. Cory in describing one of the 

 houses that he has seen says : " It was built in a marsh on the edge 

 of a shallow pond; and it was constructed of reeds, weed stalks 

 and sticks mixed with mud and was somewhat oblong in shape, 

 although from a distance it appeared to be nearly round. The top 

 of the rounded dome was three feet high, measured from the sur- 

 face of the swamp and slightly over four feet where built up from 

 the side under water. The greatest diameter was 6 feet. The 

 inside chamber measured about 20x17 inches, the height above the 

 water being about 14 inches at the highest point, the ceiling being 

 irregular. The floor of the -chamber was about 7 inches above 

 the water but slanted downward at one side to a large hole or 

 passageway leading out under water into the pond. The size of 

 the houses varies considerably, however, and many are larger." 

 (I. c., 228-229.) The writer has examined houses similarly con- 

 structed, though in many cases the materials used have been dif- 

 ferent. On March 11, 1916, the writer visited Swan lake, a body 

 of shallow water covering between seventy and eighty acres, eleven 

 miles northwest of Iowa City. In many places the water, was 

 frozen to the bottom. Between twenty and thirty muskrat houses 

 were seen, the largest being three feet high and about six feet in 

 diameter. All were built of rushes, cornstalks, and debris of dif- 

 ferent kinds and appeared to be resting upon grass hummocks. 



Such houses are used largely for shelter during the winter and 

 also for storing places for food, but it is seldom that the young 

 are born in them. Usually a singlo family occupies a house. 



High banks are often taken advantage of in the construction of 

 habitations, and in such cases the entrances to the tunnels are 

 usually under water. The tunnels extend into the bank below 

 the level of the water, and often are protected by roots of trees and 

 shrubs. These tunnels are of varying lengths, and lead up to a 

 large chamber which in many cases contains 1 a nest composed of 

 dry vegetation. Usually two tunnels lead from the nest to the 

 water, and in some instances each tunnel has two branches. Bur- 

 rows seem to be preferred to houses for winter habitation ; but in 

 shallow ponds and marshes houses become a necessity, and as cold 

 weather comes en the animals add to the old winter houses, con- 

 struct new ones, and deepen the channels leading to houses and 

 burrows. The animals do not hibernate and often make "little 

 provision for winter. Julius Knepper informs the writer that on 



