FOOD, HIBERNATION AND MIGRATION III 



another suggestion, but it cannot be seriously considered. Orientation 

 always requires that there should be a difference between different 

 parts of the field. Now, during rain, the whole country is wet — -just 

 as wet as the ponds — so that an animal using hydrotaxis as a guide 

 would lose its direction. But this is just the time when migration 

 seems most likely to occur, and the animals show no sign that they 

 have lost their way. Chapman and Chapman (1958) came to a similar 

 conclusion in their study of the African Leopard Toad, B. re<^nlaris, and 

 rightly point out that migration from one pond to another shows that 

 hydrotaxis camiot be important, citing Breder, Breder and Redmond 

 (1927) and my paper of 1935. To these examples can be added Juszczyk 

 (195 1) on R. esculenta and Martof (1953) for R. clamitans. 



Since frogs have voices, it is natural that there should be many 

 suggestions that these are used to attract other frogs to a pond in which 

 there is at least one already. This was the view, for example, of 

 Noble (193 1), and Bogert (1958) came to the conclusion that although 

 there were some inconsistencies, it was probably true that voice plays 

 a part in guiding frogs and toads to their ponds. But Cummins (1920), 

 who having camped beside an American pond for six weeks for the 

 special purpose of observing migration, should certainly know about 

 the species there, thought that voice played a minor role. He made 

 small catches on nights when there was much croaking, and large ones 

 when there was httle. The remarkable experiments of Bogert (1958) 

 must be mentioned here. The Southern Toads, B. terrestris terrestris, 

 were tested for their reactions to the voices of their own species played 

 back to them from a tape-recorder. Females on the whole moved 

 towards the instrument, but males often moved away from it. 



It is, however, necessary to take account of the species concerned. 

 Many of the American species have very loud voices — in fact the noise 

 arising from the ponds there has been described as deafening. In 

 Europe, too, there are noisy frogs. Among the causes of the French 

 Revolution, the noise of frogs, probably R. esculenta or Hyla arborea, 

 was possibly one. The nobles forced the peasants to beat the ponds all 

 night so that in the chateau near by, sleep would be possible. English 

 people are not used to tliis kind of thing from either nobles or frogs. 

 R. temporaria has a very quiet voice, and even a large colony can usually 

 not be heard more than, say, fifty yards away. Now, this is not likely 

 to be due to any insensitivity of the human ear. We have very good 

 ears (and very good eyes, too), so good that we can perceive a few 



