| Show Bats Employ Radar 1 To Dodge Obstacles When en Flying in in Dark The flying bat at night employs natural radar to avoid colliding with trees and other obstacles The little animal sends out cries too shrill to be heard by the human ear car that help it to locate things in its path Dr Robert Galambos of the University of Rochester medical medica school recounted his experiments experiment in a General Electric science forum address at Schenectady New York Bats move around almost exclusively exclusively exclusively ex ex- in complete darkness in in search of food food except except for moon and starlight Dr Galambos said That means they would collide with trees bushes and unless they had some way to tell teU where such obstacles are arc located Although bats have eyes they prefer prefer prefer pre pre- fer to live and feed in darkness The method used by the flying bat ba depends on the production of sound and the analysis of echoes As the bat flies through the air it emits a constant stream of pitched high cries which permeate the space in front of the animal If there are arc any obstacles out there like tree branches or the sound is reflected or echoed back The bat ba hears these echoes changes its course and flies into regions which are echo Physicists have invented electronic electronic electronic elec elec- I devices for detecting the supersonic sounds of bats Dr Galambos continued When Dr Donald Griffin and I were asking ourselves whether bats produced a supersonic cry we took the problem to Prof G. G W W. Pierce the expert in supersonic sound at Harvard U. U who very generously turned over to us whatever whatever whatever what what- ever laboratory space and equipment equipment equipment equip equip- ment we required The instrument we needed most was a so-called so sonic amplifier a device which converts supersonic sounds into audible ones With it we were able to show that so long a as bats fly they emit a constant stream of cries in which frequencies around cycles were particularly strong the doctor explained ned Humans cannot hear much above about cycles And as people grow older the upper limit drop lower and lower until at 60 or so soa soa soa a person is deaf above about cycles The bat emits a steady tat tat of about 30 supersonic cries a second as it cruises about in the theair theair theair air Dr Galambos said But when an obstacle lies ahead this rate just ab about ut doubles momentarily ther then drops back to 30 again when the obstacle is passed Dr Griffin and Dr watched about a hundred bats anc also experimented further to show sho the importance of the supersonic cry in another way They tied the mouth of the animal closed and then let i i fly flyaway away Those gagged animals were wen helpless in the air But as soon a athey ar arthey they cut the strings each bat bai avoided obstacles cles once again The physicists also found that thai plugged ears were as dangerous a gags for the bats the latter bump bumping bumping bumping ing into obstacles again FUndamentally Funda Fundamentally Fundamentally mentally the same vocal structure produces supersonic cries in baU bati as produces speech in man |
