Intensity of female preference for call source level in midwife toads Alytes cisternasii and A. obstetricans

Abstract

AbstractWe address the question of whether female preference exerts selection on male calling energy (souce level). We investigate whether female midwife toads express a preference between advertisement calls that have different source levels but that reach them with similar intensities (due to differences in distance). Females were presented with pairs of recordings of identical synthetic calls, recorded at the same location in the field site, and reaching the microphone at similar sound levels (69 dB peak SPL). Stimulus 'Hi source level' was recorded two meters away from the sound source but emitted with higher sound intensity, and stimulus 'Low source level' was recorded one meter away from the source but emitted with lower source level. We use a protocol of 'playback setpoints' for tests with no a priori expectations. We did not find evidence of female preference for source level in either species. Alytes obstetricans females reversed their choice when differences in intensity were lower, suggesting lower selectivity during the approach phase. We conclude that any selection on male call intensity is unlikely to occur, possibly being severely limited by calling location (male–female distance) and by transmission conditions.