FEB., 1912. MAMMALS OF ILLINOIS AND WISCONSIN CORY. 165 



a passage leading to a good-sized chamber, the floor of which is several 

 inches above the level of the water. When houses are built, they are 

 constructed of sticks, brush and mud; the top is rounded and rises 

 three or four feet above the water. Ordinary houses vary in size from 

 6 to 14 feet in diameter, although some are considerably larger. The 

 living chamber of an ordinary house is often (but not always) nearly 

 circular and has a diameter of from 4 to 5 feet and a height of from 

 15 to 24 inches; the size varies considerably and there are many smaller 

 and others decidedly larger. These chambers are almost invariably 

 supplied with two entrances. When the house is in a bank, the length 

 of the passageway to the living rooms varies, but is commonly from 10 

 to 20 feet. 



In swimming the Beaver propels itself by its broadly webbed hind 

 feet and makes little or no use of the forefeet, which are usually held 

 loosely against the body. They have a habit of striking the water 

 with their tails before diving, making a loud splash, the sound of which 

 on a calm evening can be heard a long distance. While as a rule they 

 strike the water before diving, they do not always do so, as I have, on 

 at least two occasions, seen them dive silently after the manner of a 

 Muskrat. Their work is done chiefly in the evening and at night, 

 although in unsettled districts they may not uncommonly be seen 

 swimming about in the daytime. The young are usually born in May 

 and the average number in a litter is 4 or 5, sometimes 6 and, according 

 to Morgan, very rarely 7 or 8 (/. c., p. 221). The extraordinary number 

 of 10 young Beavers in a litter is recorded by Brown.* 



The food of the Beaver consists principally of the bark and tender 

 twigs of the poplar or aspen and the willow. It also eats the bark of 

 other trees and bushes and sometimes roots and leaves. To procure 

 its store of winter food it cuts down trees and transports the logs and 

 branches to the vicinity of its house or burrow, where they are stored 

 under water to be used when needed. In many cases a hole in the ice 

 is kept open to enable the animals to come out when they please, and 

 through which an extra supply of food can be taken to the house after 

 the river or pond is frozen over. Numbers of small trees are cut down, 

 but larger ones having a diameter of 12 to 15 inches are by no means 

 unusual. Trees two feet in diameter are occasionally felled by these 

 animals and Lewis and Clark record one measuring nearly three feet.f 

 In places where the trees are separated from the water by a marsh, 

 the Beavers dig canals to enable them to float the trees and larger 

 branches, after they are cut up into sections, to the pond. The larger 



* Brown, R. Proc. Linn. Soc. Lond., Zoology, 1868 (1869), p. 367. 

 t Lewis and Clark, Ex. Longman's ed., p. 146. 



