i8 



The 



rion (dead animals). But most carni- 

 vores hunt and kill. Bears, wolves, foxes, 

 skunks, and many others have blunt, 

 strong claws. In cats, tigers, and lions the 

 sharp claws are pulled back w hen not in 

 use. 



Gnawing mammals. We all know the 

 gnawing mammals, or rodents. There 

 are about 2000 species spread over prac- 

 tically the whole globe, in the hot 

 desert and in the arctic snow and ice. 

 Some burrow in the ground, some live 

 in trees, and others live in the water. 

 You know rabbits, rats, mice, squirrels, 

 and woodchucks. You may have seen 

 beavers, or perhaps the dams they build. 

 If you live in our West you have heard 

 the whistling marmot; you have seen the 

 prairie dogs on our great plains. Most 

 rodents are small and timid. The two 

 pairs of front teeth (incisors) can in- 

 flict an ugly wound but unless cornered 

 the animal will not bite. The front teeth, 

 used for gnawing and chiseling, are 

 worn down by constant use. But they 

 keep growing as long as the animal 

 lives. 



Mammals that live in the sea. A whale 

 is so dependent on the water and so 

 fishlike in shape and general appearance 

 that at first glance you might not classify 

 it as a mammal. But it has the two dis- 

 tinguishing characteristics of a mammal: 

 it has mammary (milk) glands and its 

 skin, although mostly naked, has a few 

 bristles of hair. Like other mammals it 

 is warm-blooded and brings forth its 

 young alive. Whales have large amounts 

 of fat called "blubber." This protects 

 them against the cold. Alan converts 

 the fat into oil, obtaining as much as 1 50 

 barrels of oil from a good-sized whale. 



Living Things of the Earth unit i 



There have been many fanciful stories 

 about whales. A \\ hale cannot swallow 

 a man whole nor does it even attack 

 man except when fighting back. And 

 whales do not spout water. When a 

 whale comes to the surface and breathes 

 out, the water vapor in its hot breath 

 condenses (just as yours does on a cold 

 day) and the little drops of water that 

 are formed look like a stream of water 

 shooting up into the air. 



There are other mammals that live 

 in the sea: walruses, seals, and sea lions. 

 Examination of their structure and par- 

 ticularly their teeth shows that they are 

 really carnivores. The seals and sea lions 

 spend part of the time on land resting 

 or waddling about awkwardly by using 

 their flippers as legs. 



Mammals that fly. The bats are mam- 

 mals that fly. They can flv^ better than 

 many birds. Being mammals, they do 

 not have feathers; they have hair. Bats 

 resemble a tailless mouse with bie ears 

 and large folds of skin under the arms 

 which are used as wings. All day long 

 they hang head down, hooked to the 

 rafters of some buildine^ or in a cave or 

 hollow tree. Some species sleep in col- 

 onies of several thousands, coming out 

 at night to search for food. Most bats 

 live on insects, some eat fruits, and a 

 few, the vampire bats, suck the blood 

 of other mammals. It is not true that 

 bats fly into people's hair nor do our bats 

 hurt \'ou in any way. 



Simple mammals. The 7f7arsi/pifils 

 (mar-soo'pee-els) are simpler than the 

 mammals you have just read about. 

 Among the marsupials the young are 

 born in a very undeveloped and helpless 

 state, and the female carries the young 



