432 PRACTICAL ZOOLOGY 



of open country and dig burrows in the ground. Their food 

 consists of grain which they carry into their burrows in cheek 

 pouches. The prairie " dogs " (Fig. 300) are burrowing rodents 

 that live on our western plains in colonies of from forty to one 

 thousand. They feed upon grass and other vegetation. The 

 woodchucks, or ground " hogs," also live in burrows ; but are usu- 



FIG. 300. Prairie dog at the entrance to its burrow. 

 (Photo, by Brownell.) 



ally not colonial, and prefer hillsides or pasture land for their 

 homes. They feed on clover and other grass. The flying 

 squirrels are delicate nocturnal rodents that spend the day asleep 

 in a nest, usually in a cavity in a tree. They possess a thin 

 fold of skin between the fore and hind limbs on either side, 

 which, when spread out, acts like a parachute to sustain the 

 animal in the air. 



The beaver family contains the largest gnawing animals in 

 North America. They are adapted for life in the water, possess- 

 ing webbed hind feet and a broad, flat tail. The dams of wood, 

 grass, and mud made by beavers are constructed for the purpose 

 of farming ponds in which houses are built with underwater 

 entrances (Fig. 301). 



