Fes., 1912. Mammats or ILLINoIs AND WIscoNnsIN — 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 (J. 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.t 
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., Zodlogy, 1868 (1869), p. 367. 
t Lewis and Clark, Ex. Longman’s ed., p. 146. 
