CLASS MAMMALIA. MAMMALS 



485 



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Figure 357. Chipmunk ['lamias). A beautiful 

 little rodent that lives in crevices in rocks, under 

 logs, or in burrows in the ground. It becomes quite 

 tame if fed and is a favorite of children and adults 

 in some parks. (Courtesy of N.Y. Zoological So- 

 ciety.) 



Toothless mammals 



The toothless mammals either have no 

 teeth or a few that are not well developed. 

 They include sloths, anteaters, and armadil- 

 los. Sloths inhabit the tropical forests of 

 Central and South America, live in the 

 treetops, and hang to the underside of the 

 branches by means of two or three long 

 curved claws. The great anteater (Fig. 

 354C) has a long, narrow snout, long claws 

 on the forefeet with which to tear open 

 anthills, and a long, slender tongue serving 

 to capture ants. Armadillos (Fig. 354E) pos- 

 sess armor of bony scutes; and when they 

 are disturbed, some roll up into a ball for 

 protection. 



Gnawing mammals 



Among the gnawing mammals are squir- 

 rels, beavers, rats, mice, pocket gophers, 

 porcupines, chinchillas, and golden ham- 

 sters. Their front teeth are efficient chisels 

 and grow constantly. The common tree 

 squirrels are all excellent climbers. Chip- 

 munks usually live on the ground among 

 rocks. Ground squirrels are sometimes called 

 "gophers" in northeastern states where true 

 gophers do not occur. Prairie dogs of our 

 western plains are burrowing rodents. 

 Woodchucks or ground hogs also live in 

 burrows. Beavers (Fig. 354F) are adapted 

 for life in the water, possessing webbed 



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Figure 358. The chinchilla. These animals were 

 introduced into the United States in 1923 by 

 Chapman, who obtained 11 animals from Chile. 

 Since then many chinchilla ranches have been estab- 

 lished in the United States. Chinchilla fur has a 

 downy softness, but it is not as serviceable as some 

 other furs. (Courtesy of N.Y. Zoological Society.) 



hindfeet and a broad flat tail. Another 

 adaptation is ear and nose valves, which 

 close under water. The beaver can gnaw 

 logs below the surface of water as well as 

 above. The common house mouse, the 

 Norway rat, and black rat have all been in- 

 troduced into this country from the Old 

 World. Porcupines (Fig. 337) possess 

 spines, which normally lie back, but can be 

 elevated by muscles in the skin. The chin- 

 chillas of South America are of medium size 

 and noted for their very soft fur. 



Omnivorous mammals 



These are mammals which eat both plant 

 and animal food; examples are common 

 house rats, red fox, bears, raccoons, pigs, and 

 man. 



Carnivorous mammals 



The flesh-eating mammals live in two 

 types of habitats, terrestrial and aquatic. 

 The teeth of carnivores (Fig. 347) are per- 

 haps their most characteristic feature. The 

 front teeth or incisors are small and of little 

 use; the canines are very large and pointed, 

 enabling the animal to capture, kill, and tear 

 its prey; the premolars and the first molar in 

 the lower jaw have sharp cutting edges; the 

 other molars are usually broad crushing 



