MIGRATION AND SEX RECOGNITION IN FROGS 333 



fully about the joint between femur and crus, then liberated in 

 the wood about 1000 feet away from the pond. Only four indi- 

 viduals were recovered, the remainder probably having migrated 

 to a pond on the opposite side of the wood. These catches were 

 not included in the trap record. The dates of capture follow: 

 a male, April 1st; a male, April 12th; a female, April 16th, and 

 a female, April 18th. Reference to table 1 shows that a cool 

 spell intervened between the trapping of the first individual and 

 of the last three. That this fact alone was not responsible for 

 the extended time requirement of the last three individuals is 

 evidenced first by the return of one frog as early as the next 

 day after liberation, and second by the migrations of other frogs 

 in the interval. 



To voice has been generally attributed the function of at- 

 tracting frogs to their breeding ponds. In the species under con- 

 sideration the males are provided with huge resonating sacs 

 opening iijto the mouth cavities, whose presence results in a 

 marked increase in the volume of sound. A general account of 

 voice is extracted from Holmes ('12) : "The voice of the male is 

 louder and deeper than that of the female and is more often 

 heard. In large frogs the notes are deeper than in small ones. 

 The notes of frogs are more often heard in the breeding season, 

 when they are supposed to serve the purpose of a sex call. In 

 the summer, however, it is not unusual to hear the croaking of 

 frogs, especially in the evening. A damp atmosphere is con- 

 ducive to their song, and for this reason the voices of these 

 animals are often heard upon the approach of a shower." The 

 writer did not hear female leopard frogs croaking during the 

 breeding season of 1914 except under circumstances which would 

 permit of explanation by reflex croaking in response to tactual 

 stimulation. Males, on the other hand, not only exhibited the 

 croaking reflex, but also croaked of their own accord. The 

 chorus of male toads has been studied by Courtis ('07) and 

 Miller ('09). Their results indicate that voice in this form does 

 serve as a sex call, but the writer's study of frogs does not sup- 

 port this view, at least it indicates that the chorus is not neces- 

 sary to incite or direct migration. 



