ECHO-LOCATION 187 



We have likened the sonar of bats to the radar of man, 

 which was first developed for use in war, for locating hostile 

 aircraft in the dark or when far beyond the range of vision 

 — radar has since proved to have uses equally valuable 

 to the arts of peace. In war as soon as any new device 

 is produced by one side the other seeks means for frust- 

 rating it, and many different ways were invented for 

 jamming or otherwise rendering radar useless. Surprising as 

 it may seem, it appears that nature too has long ago invented 

 countermeasures to combat the sonar of bats, for it is now 

 reported that certain moths have ears sensitive to ultrasonic 

 vibrations, and that they take violent evasive action on being 

 "looked at" by a bat's sonar system so that the moths can 

 escape; man has not been alone in inventing air-borne 

 "anti-bandit" apparatus! Perhaps we may yet find that 

 some moths actually have a system of jamming the bat's 

 sonar. 



Few people have ever heard a whale's voice, and until 

 recently zoologists believed that whales were completely 

 dumb. Yet Arctic whalers had long known that at least one 

 kind of whale, the Beluga or White Whale, sometimes makes 

 sounds audible to men on the deck of a sailing ship. When 

 these creatures were near or underneath the ship a whistling 

 musical trill was heard so often that the whalers nicknamed 

 them "sea canaries". Zoologists considered that the sounds 

 were probably made by the whales releasing a fine stream 

 of bubbles from the blowhole, and that they were not a true 

 voice. 



The widespread use of hydrophones for undersea listening 

 during the war showed that the popular conception of the 

 "silent depths" of the ocean was far from correct. Many sea 

 creatures, from shrimps and crawfish to fishes, dolphins and 

 whales, keep up a chorus that sometimes rises to little short 

 of a general uproar — to ears that can hear it. Animals that 

 make noises can, presumably, also hear them. Here again 

 the whalers have long known how easily a nearby whale is 

 frightened away by a sudden sound, as of a bucket dropped 

 on deck. Asdic, another war-time device used for echo- 

 locating underwater objects by ultrasonic vibrations, has 

 given us more knowledge about whales, for it was soon 



