THE LANGUAGE OF ECHOES 



proximately 4 meters per second) that with the smaller 

 wires it often has time for only 2 or 3 additional pulses 

 above the number it would have employed had there 

 been no wire in place. All these facts testify that the 

 echolocation practiced by bats is a refined, accurate 

 method of orientation, not merely a crude sort of 

 gropmg. 



Bread upon the Waters 



Nor do these examples by any means exhaust the list 

 of difficult tasks which bats accomplish with some aid 

 at least from echolocation. Certain of the whispering bats 

 catch insects, small birds, or lizards that are resting on 

 vegetation, but we are not sure that they do this by means 

 of echolocation. They may simply listen to characteristic 

 sounds coming from their prey. More amazing is the fact 

 that four different species of the FM bats make their liv- 

 ing by catching fish. This they do by flying just above the 

 surface of the water and every now and then dipping 

 their hind feet just below the surface. The claws on these 

 feet are long, curved, and sharp, and the bats manage 

 to gaff small minnows often enough to fill their stomachs 

 every evening (as shown in Fig. 13 ) . When fishing in this 

 way on the darkest nights (and often with mist rising 

 from the water) , they emit a rapid series of chirps much 

 like those of their insect-catching relatives. The gap be- 

 tween the two types of food gathering is not as great 

 as it might at first seem, for the insectivorous bats drink 

 by skimming the surface of the water and dipping their 

 chins just deep enough to secure a drop of water at a 

 time. This requires fine control, for a millimeter too deep 

 would surely result in a dunking. These insectivorous 

 bats also catch insects resting on the water surface, so 

 perhaps it was a small step from this habit to reach for 



95 



