ECHOES OF BATS AND MEN 



fish below the surface. In any event, the fish-catching 

 species make much of their living in this way, and during 

 their recent evolutionary history a relatively small ana- 

 tomical adaptation has resulted in the specialized fish- 

 gafiSng claws. 



When I have watched these bats in Panama, I have 

 seen no sign that the fish were moving or disturbing the 

 surface of the water in any way. Often it was glassy 

 calm, and the bat flew for hundreds of feet a few inches 

 above the surface, quickly lowering the hind feet into the 

 water for a short distance and then raising them while 

 continuing its low-altitude searching flight. How do these 

 bats know where fish are to be captured? They are evi- 



Fig. 13. Motion pictures of fishing bats actually gaf- 

 fing minnows provided the model for this drawing. 

 Prentice Bloedel took the photographs. 



dently selective in their fishing, for they fly long distances 

 just above the water and only rarely dip their claws be- 

 neath the surface. Since the fishing occurs on dark and 

 misty nights, it is most unlikely that the fish could be 

 seen and still less probable that they emit any sound 

 audible to the bat flying in the air above the surface. 

 Could it be that the fish-catching bats detect echoes from 

 fish beneath the surface? At first glance this may seem 

 only a slight modification of the process by which closely 

 related bats catch insects in the air. But the physical dis- 

 continuity between air and water makes the transmission 



96 



