Male Phonotropism and Answer Calls Elicited by Female Vocalizations in the African Clawed Frog, Xenopus laevis

Abstract

Male and female African Clawed Frogs (Xenopus laevis) produce calls and engage in dueting in both silt-filled ponds and laboratory aquaria. Previous research has established that males produce different answer calls in response to receptive (11–12 Hz click rate) and nonreceptive (click rate of 4 Hz) female calls. In the present study, in addition to male answer calls, male phonotropism behaviors were measured for the first time during playbacks of natural female rapping and ticking calls as well as synthetic stimuli consisting of ticking calls with 90-msec interclick intervals (ICIs) and rapping calls with 250-msec ICIs. Also, the results show that males approach a loudspeaker significantly more often in response to rapping calls and remain longer in the proximity of the speaker. Moreover, males produce answer calls more frequently in response to female rapping calls and produce few answer calls in response to female ticking calls. Synthetic ticking calls with 90-msec ICIs evoked an intermediate phonotaxis response, whereas synthetic rapping calls with 250-msec ICIs evoked the same level of phonotaxy as do natural ticking calls. These results show that male phonotaxy is strongly, although not entirely, determined by the rhythmic characteristics of female calls, whereas antiphonotaxy appears to be determined by female call rhythm alone.