216 GNAWING ANIMALS 



supplies of food-wood for winter use, when the surface is 

 frozen for a long period. 



Sometimes when food-wood on a beaver pond becomes 

 scarce, the animals dig canals into places where fresh supplies 

 can be cut and floated down to the pond. These canals are 

 usually about two feet wide. 



A Beaver is readily recognized by its very flat, hairless, 

 and scaly tail, which beyond the hair of the body is about 

 9 inches long by 4 inches wide. The tail is never used as a 

 trowel in building dams, but only as a propeller in swimming. 



Dam-building is done in two ways. With his front feet 

 the animal digs up soft mud, holds the mass with his fore 

 legs against his breast, and swims with it to the dam. There 

 he deposits it where it is most needed, and pats it down with 

 his front feet. To strengthen the structure, he brings sticks 

 4 or 5 feet long, and I or 2 inches in diameter, from which 

 he has eaten the bark. These he usually lays upon the dam, 

 crosswise or nearly so, and fills in between them with mud. 



When Beavers have to build a dam exceeding 50 feet in 

 length, to flood low ground, they usually lay it out with a 

 curve up-stream. The dam built by the Beavers in the New 

 York Zoological Park is about 40 feet long, and 3 feet high, 

 and quite sharply curved up-stream. 



In most localities inhabited by Beavers, the banks of the 

 streams are so low that the animals cannot burrow into 

 them, and consequently they build houses for themselves. 

 The ordinary Beaver house is a huge pile of neatly trimmed 

 6-foot poles, with all spaces between the sticks plastered full 

 of mud. The one in the Zoological Park is about 15 feet in 



