CLASS MAMMALIA. MAMMALS 



483 



Figure 355. Koala, Australian "teddy bear." Fe- 

 male first carries young in a pouch, then later on 

 her back, as is shown in this photograph. Adults 

 are about two feet long. They live in trees and feed 

 on the leaves of the giant gum (eucalyptus) tree of 

 this region. (Courtesy of Victorian Railways.) 



pieces with the sharp-pointed cusps on their 

 hind teeth. Most of them travel on the 

 ground, but a number of them hve in bur- 

 rows, a few are aquatic, and some hve in 

 trees. Moles (Fig. 354B) and shrews are 

 common species in this country. The shrews 

 are of special interest for several reasons: 

 they are the smallest mammals (some weigh 

 less than a dime) and their metabolic rate 

 is the highest of all animals in this group. 

 The masked shrew is reported to breath 

 850 times per minute and has a pulse rate 

 of about 800 beats. A poisonous substance 

 in the saliva helps the shrew in the capture 

 of mice and other prey. 



The only true flying mammal 



Bats possess forelimbs that are modified 

 for flight. The forearm and fingers are 



elongated and connected with each other, 

 with the hindfeet, and usually with the tail, 

 by a thin leathery membrane. Because of 

 their remarkable powers of locomotion, bats 

 are very widely distributed, occurring on 

 small islands devoid of other mammals. 

 Most of the more than 600 species are small 

 and chiefly nocturnal. During the day most 

 of them seek darkened retreats such as caves, 

 tree hollows, and houses, where they hang 

 head downward, suspended by the claws of 

 one or both legs. At night, bats fly about 

 actively in search of insects. Some live on 

 fruit, and a few suck the blood of other 

 mammals. The little brown bat, which is 

 abundant in eastern North America, appears 

 to have a well-developed homing instinct. 

 Experiments show that it tends to return 

 to the same cave used as a davtime re- 

 treat. 



The true vampire bats inhabit tropical 

 America. They live on the blood of horses, 

 cattle, and other warm-blooded animals, and 

 sometimes they attack sleeping human be- 

 ings. Their front teeth are very sharp, but 

 the back teeth have practically disappeared. 

 The skin of their victims is cut by the front 

 teeth, and the oozing blood is lapped up. 

 It has been proved that vampire bats in 

 Mexico transmit paralytic rabies, a disease to 

 which many animals, including man, are 

 susceptible. Other diseases known or sus- 

 pected to be vampire-bat-borne include yel- 

 low fever, scrub typhus, Chagas' disease, all 

 affecting humans; and a tropical tr^pano- 

 some disease of horses known as murrina. 



The expression "blind as a bat" indicates 

 a common misconception, for the bat does 

 have eyes and appears able to see well. 

 Nevertheless, a completely blinded bat can 

 fly about in a room hung with crisscrossing 

 silk threads without touching the threads. 

 It guides itself by the echoes of supersonic 

 sounds it makes which are thrown back from 

 objects in its path. Thus it will be seen that 

 long before man ever thought of radar, the 

 bat employed this principle. It can catch its 

 food in pitch darkness while dodging all 

 sorts of objects. 



