484 



THE NATIONAL GEOGRAPHIC MAGAZINE 



many mice are known to have continuous 

 series of notes which are as evidently 

 songs as the utterances of birds. Some 

 of these notes, as in the case of singing 

 mice, have a remarkably musical char- 

 acter, similar to the warblings of cana- 

 ries. Various unrelated species of mice 

 have been observed singing, and a closer 

 study of the life habits of these small 

 animals may develop the fact that all are 

 songsters to some degree. 



House rats and mice have, undoubtedly, 

 been parasitic about the haunts of man 

 from early times. From Asia they have 

 accompanied him through his advance in 

 civilization. With the growth of com- 

 merce they have traveled around the 

 world, becoming transplanted to all lands 

 and thriving in all climates. In various 

 parts of America they have not only be- 

 come pests about human habitations, but 

 where climatic conditions were favorable 

 have reverted to the wild state and are 

 competing with the native species in the 

 fields. 



Of all the small mammals none have 

 become modified to such an extent as the 

 bats. As a group these mammals are of 

 world-wide distribution except in the in- 

 hospitable polar regions. They are true 

 mammals and present an extraordinary 

 variation in - size, from tiny little crea- 

 tures, almost as small and fragile as 

 butterflies, to the huge fruit-bats, with a 

 spread of wings like that of a wild goose. 



BATS WITH BULLDOG FACES 



The heads of bats are strangely sculp- 

 tured, some being smoothly contoured 

 and shaped like those of little foxes ; 

 others appear like miniature bulldogs ; 

 and still others have curious cartilaginous 

 nose-leaves upright on the muzzle. Some 

 have the entire face molded into a hide- 

 ous mask repulsive to look upon. 



Their habits are equally varied to meet 

 special conditions: Some are eaters of 

 fruit alone ; others feed solely upon in- 

 sects, while others bite other mammals, 

 including man, for the purpose of drink- 

 ing the oozing blood, upon which they 

 subsist. All are nocturnal, but some ap- 

 pear late in the afternoon, before the sun 

 sets ; most species, however, wait until 

 the shades of night have covered the 

 earth. 



Throughout the world the majority of 

 the species of bats feed upon insects, but 

 there are many fruit-eaters. The teem- 

 ing insects and plant life of the tropics 

 afford a never-failing food supply, and 

 the center of abundance of these animals 

 IS found there. In some localities be- 

 tween twenty and thirty kinds of bats 

 exist, with such vast numbers of indi- 

 viduals that the bat population far out- 

 numbers all other kinds of mammals com- 

 bined. 



ANIMALS THAT PUT THEMSELVES IN COLD 

 STORAGE 



In the northern parts of the Old and 

 New Worlds many mammals, including 

 bears, marmots, prairie-dogs, ground- 

 squirrels, and jumping mice, pass a large 

 part of the winter months in a lethargic 

 sleep called hibernation. While hibernat- 

 ing these animals have extremely slow 

 and slight heart action and their bodily 

 temperature falls far below the normal 

 of their active periods. During the most 

 profound hibernation an animal may be 

 awakened if brought into a warm tem- 

 perature, but when again put into the cold 

 at once returns to sleep. 



Preparatory to this sleep, during the 

 summer and in the autumn, the hibernat- 

 ing mammals become exceedingly fat. 



It has long been generally accepted that 

 the fat thus accumulated was for the 

 purpose of being gradually absorbed to 

 nourish the animals during their long 

 fast. As a matter of fact, during this 

 period the bodily functions appear to be 

 practically suspended and the animals 

 may be said to be in cold storage. This 

 is evident from the fact that observations 

 have been made of ground-squirrels, and 

 even bears, emerging in spring, after 

 their long winter sleep, practically as fat 

 as when they retired in fall. Hibernat- 

 ing animals become extremely active as 

 soon as they come out in spring and 

 quickly lose the fat which should be of 

 special service to them, owing to the tem- 

 porary shortage of food they experience 

 at this season. 



Most hibernating species do not retire 

 for the winter until cold weather is at 

 hand, in September or October, at times 

 remaining out until after the first snow 

 has fallen. The animals which retire 



