270 



VERTEBRATA 



The squirrels (Sciuridce) are represented by the chip- 

 munks or ground-squirrels, usually striped, the red squirrel 

 living in northeastern United States, and the gray squirrel 



inhabiting the for- 

 ests east of the 

 Rocky Mountains. 

 The red squirrel 

 deserves to be ex- 

 terminated, as it 

 drives away the 

 gray squirrel and 

 destroys the eggs 

 and young of the 

 song birds. The 

 marmots are bur- 

 rowing rodents 

 much larger than 

 the true squirrels. 

 The woodchuck (Marmota monax) abounds nearly every- 

 where east of the Rockies. Instead of storing up food 

 like the squirrels it hibernates during the cold season, and 

 when removed from its burrow in winter appears to be in 

 an unconscious condition. The heart beats but a few 

 times per minute and respiration is very slow, so that the 

 food stored up largely in the form of fat in its own body 

 enables it to pass the cold season without eating. The 

 prairie dog, ranging from Texas to Canada, is a social 

 animal dwelling in large colonies sometimes more than 

 fifty miles in length. 



The rats and mice (Muridce) number about one hundred 

 <and seventy-five species in North America. The muskrat 



FIG. 306. A moose pushing its way through the 

 underbrush. 



