THE VERTEBRATE ANIMALS 



313 



Skull of a dog. Notice the size and shape of 

 the canine teeth. 



many, as the bear and lion, have homes or dens to which they retreat. 

 Some (for example, bears and raccoons) live at least part of the time 

 upon berries and fruit. Seals, sea lions, and walruses are adapted 

 to a life in the water. 

 Especially in the seals, the 

 hind limbs are almost use- 

 less on land. Some of the 

 fur bearers, as the otter 

 and mink, lead a partially 

 aquatic life. Others in this 

 great group prefer regions 

 of comparative dryness, as 

 the inhabitants of the 

 South African belt.- A few 

 have come to live most of 

 their time in the trees, the raccoon being an example. Many 

 have adaptations for food getting and escape from enemies; the 

 seasonal change in color of the weasel is an example of an adapta- 

 tion which serves both of the above purposes. This is only one 

 of hundreds of others that might lie mentioned. 



Economic Importance. — The Carnivora as a group are of much 

 economic importance as the source of most of our fur. The fur seal 



fisheries alone amount to many 

 millions of dollars annually. 

 Otters, skunks, sables, weasels, 

 and minks are of considerable 

 importance as fur producers. 

 Our domestic cats (particularly 

 deserted cats) are such factors in 

 the extermination of our native 

 birds that their place as house 

 pets is seriously questioned 

 by some people. In India tigers, and in Africa lions, are man- 

 eating in certain localities, and in our own country wolves, 

 pumas, and wild cats do some damage. 



Rodents. — Mammals known as rodents have the teeth so 

 modified that on the upper and lower jaw two prominent incisor 

 teeth can be used for gnawing. These teeth keep their chisel-like 



The California sea lion (Zalophus call/or- 

 nianua). Photographed in the Philadel 

 phia Zoological Gardens by Davison. 



