246 THE ANIMALS AND MAN 



and the constant rubbing on each other. The food of rodents 

 is chiefly vegetable. 



Of the hares and rabbits the cottontail {Lepus nuUalli) 

 and the common jack-rabbit {L. campestris) are the best 

 known. The cottontail is found all over the United States, 

 but shows some variation in the different regions. There are 

 several species of jack-rabbit, all limited to the plains and 

 mountain regions west of the Mississippi River. The food of 

 rabbits is strictly vegetable, consisting of succulent roots, 

 branches, or leaves. Rabbits are very prolific and yearly 

 rear from three to six broods of from three to six young each. 

 There are two North American species of porcupines, an 

 Eastern one, Erethizon dorsatus, and a Western one, E. 

 epixanihus. The quills in both these species are short, being 

 only a few inches in length, and are barbed. In some 

 foreign porcupines they are a foot long. They are loosely 

 attached in the skin and may be readily pulled out, but they 

 cannot he shot out by the porcupine, as is popularly told. 

 The little guinea-pigs (Cavia), kept as pets, are South 

 American animals related to the porcupines. 



The pocket gophers, of which there are several species 

 mostly inhabiting the central plains, are rodents found 

 only in North America. They all live underground, 

 making extensive galleries and feeding chiefly on bulbous 

 roots. The mice and rats constitute a large family of 

 which the house-mice and rats, the various field-mice, the 

 wood-rat {Neotoma pennsylvanica) and the muskrat {Fiber 

 zibethicus) are familiar representatives. The common brown 

 rat {Mus decumanus) was introduced into this country 

 from Europe about 1775, and has now nearly wholly sup- ■ 

 planted the black rat {M. rattus), also a European species, 

 introduced about 1544. The beaver (Castor canadensis) 

 is the largest rodent. It seems to be doomed to extermin- 

 ation- through the relentless hunting of it for its fur. The 

 woodchuck or ground-hog {Arctomys monax) is another 



