ACOUSTIC COMPETITION IN MALE MIDWIFE TOADS ALYTES OBSTETRICANS AND ALYTES CISTERNASII - RESPONSE TO NEIGHBOR SIZE AND CALLING RATE - IMPLICATIONS FOR FEMALE CHOICE

Effects of neighbor on male calling behavior was studied through playb ack experiments of synthetic calls to males of two species of midwife toads. The responses of resident males were scored considering two tem poral parameters (call duration and calling rate) and one spectral par ameter (dominant frequency). The sounds used for the playback tests in cluded two levels of fundamental frequency (correlated with male size) and two levels of call repetition rare. In both species, resident mal es only changed their calling rate in the presence of an intruder, and the response was different for synthetic calls with two levels of dom inant frequencies and with two calling rates. Resident size was nor si gnificantly correlated with the magnitude of the change in the calling rare. On the other hand, resident calling rate was significantly and positively correlated with the magnitude of the increase in calling ra te of the stimulus. The maximum relative increase in calling rate was observed in A. cisternasii. In phonotaxis tests, females are preferent ially attracted to calls emitted at a higher rate confirming the impor tance of changes in calling rate for female attraction.