Acoustic competition in male Pelodytes ibericus (Anura: Pelodytidae): Interactive playback tests

Abstract

The advertisement call of Pelodytes ibericus (Anura: Pelodytidae) is composed of two distinct pulsed notes (A and B). A single A note is always emitted at the beginning of a call, and it may be followed by a sequence of 0-9 B notes. We studied the role of vocalizations in male-male competition by performing a playback experiment on naturally calling focal males by mimicking the effect of competing male calls with call bouts of different number of Bs. The A and B notes used as stimuli were standard natural calls selected through audiospectrogram correlations. Field tests were performed with a portable computer and interactive playback software. Males responded to stimuli by increasing call repetition rate (= decreasing intercall interval), pulses/note and note duration. Other static call parameters (frequency and number of pulses) did not increase and did not change linearly with the number of B notes in the stimulus. In addition, males did not increase the number of B notes in their calls, and the number of B notes/call was not correlated with the number of B notes in the stimulus. The biological significance of the repetition of the number of B notes remains unknown, but it does not appear to have a simple role in male-male competition.