332 THE BOOK OF THE ANIMAL KINGDOM 



capable of moving without creating any sound audible to a human 

 being. 



As it catches its food upon the wing it is necessary that the Bat 

 should have a wide-cleft mouth. Such it possesses, and thus reminds 

 us of the wide aperture of the Nightjar (which feeds upon very 

 similar creatures to the Bat, and is a nocturnal bird), and also the 

 more familiar Swallow. 



The sharp, needle-like teeth of the Bat enable it to bore through 

 the outer covering of its prey, and it uses its teeth only for biting 

 and boring, gnawing and grinding being unnecessary. The short 

 neck is in keeping with the other structure of the body, as a long 

 neck would be of no service in view of the fact that when upon the 

 wing it is an easy matter for the head and body to be turned together 

 in any desired direction. 



Unlike birds, the Bat is unable to undertake a perilous journey 

 over land and sea, hence at the approach of Winter it does not migrate 

 to a warmer climate where an abundant food supply would also be 

 procurable, although it is stated that one species in North America 

 does migrate to warmer climes. Thus, when the chill of Autumn is 

 upon us, the Bat adopts the habit of hibernating, and for this 

 purpose it selects a hiding-place where it may be secure for the 

 Winter. In such a snug retreat as a cave, roof of a house or barn, 

 chimney, hollow tree, quarry, cellar or among ruins, this mammal 

 seeks out a congenial spot where it may rest during the cold weather, 

 and large numbers of them may very often be found hibernating 

 together, hanging up by their feet, unconscious, stiff and motionless. 

 Dr. Schmeil states that when in this condition the pulse only beats 

 about once every three minutes, and the respirations are rare and 

 hardly perceptible. 



It is essential, of course, that while in this comatose state the Bat 

 should be guarded against sinking below a certain minimum of body 

 heat, and this is provided against by means of the uncommonly 

 thick, heavy covering of the body, and also the flying membrane, 

 which, by enfolding the body similar to a mantle, "likewise forms a 

 protection against an excessive loss of body heat, since the air 

 enclosed within it acts as a bad conductor of heat." 



During the time it is out and about the Bat stores up within its 

 body a supply of fat which stands it in good stead when it is neces- 

 sary for it to go into temporary retirement, for "although during its 

 Winter sleep the Bat is suspended like a corpse, life is by no means 



