392 



MAMMALIA 



The Alpine marmot is. a similar form, hibernating a dozen in a group, 

 packed into a hair-lined burrow. 



The North American beaver {Family Castoridae), an aquatic 

 rodent, has a heavy body, webbed hind feet, and a large flat tail. 

 Contrary to the statements of some nature fakers, the tail is not 





ii^'^ 







Fig. 221. y^, chipmunk. 5, flying squirrel. C, prairie dog. D, beaver. 

 L. A. Fuertes. Courtesy of Slingerland-Comstock Publishing Co.) 



(From 



used as a trowel or a sledge, but as a danger signal and in swimming 

 and diving. The beavers fell trees up to eighteen inches in diameter 

 and quickly dam streams to flood the entrance to their burrows. 



The largest family of rodents and the most important economi- 

 cally is the family Muridae to which belong the rats and the mice. 



