Acoustic Competition in Male Pelodytes ibericus (Anura: Pelodytidae): Interactive Playback Tests
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.Abstract
Audiospectrogram and oscillogram of notes A and B of an advertisement call. Male snout–vent length, 33 mm; water temperature, 14.4 C
Results of the single stimulus tests. Each series of 4–6 circles corresponds to the results for a single male and a single call parameter. The first plot of each series (open circle) represents values for the calling male before being subjected to a stimulus (control). Solid circles to the right of each open circle show responses to computer-generated calls consisting of A, AB, ABB, ABBB calls, and ABBBBBB calls, respectively. The whiskers represent the standard error