THE 



AMERICAN NATURALIST 



Vol. XLI Noveinher, 1907 No. 491 



RESPONSE OF TOADS TO SOUND STIMULI 

 S. A. COURTIS 



The sense of hearing in frogs has been critically studied by Dr. 

 R. M. Yerkes. He tested the effect of a great variety of sounds 

 upon frogs in their natural habitat and states that "To no sound 

 have I ever seen a motor response given."* The sounds ranged in 

 pitch from a low tone in imitation of the bull frog's croak to a shrill 

 whistle, and in loudness from the fall of a pebble to the report of a 

 pistol. H<- savs further, — "One can a])proach to within a few 

 feet ot a i^rccii tr..-- or bull frog and make all sorts of noises without 



I hav'e rcpcatedls crept up very ch.se 1o fn-u's kirpinir ""iiivself 

 screene.l from them b.N l.ii.lie. <.r tie.", an.l made vaiiou. mmuhIs, 

 but Ikuo nexer m.<-( (<e<h .1 in m arinu an annual into a motor response 

 so long as I was invisil)le. Apparently they .h-pend ahn..>t entirely 

 upon vision for the avoj.huice of dan-ei>. . .Many ohMTvcr. have 

 told me that froo-s could hear the human voice and that slight 



In no case, li.mcNc!-. Ikinc ^n, h obMM\ei. lu-cn -Mv to'a.M-n that 

 the animals were unallected i)V vi-nal stinmh at th(^ >-m\\v time . . . 

 There is, however. concln>iv." v^u\v^u■v that the animal.^ hear one 

 anoth.M', an<l the pn.bal.iHtv i^ vrrv -nat tluit they hear a wide 



