Vocal Responses to Conspecific Calls in a Neotropical Hylid Frog, Hyla ebraccata

We investigated the vocal behavior of Hyla ebraccata in Central Panama. The advertisement call consists of a pulsed buzz-like primary note (approximately 3,000 Hz, 0.16 s, 95 pulses/s) followed by 0-4 click-like secondary notes. The aggressive call consists of a primary note with a much higher pulse repetition rate (9 = 265 pulses/s) given with or without secondary clicks. Isolated males give mostly single-note (primary note) calls, whereas males in choruses usually give calls with click notes. Males respond to the approach of non-calling individuals by giving a series of primary notes without clicks. In field playback experiments, stimulus tapes of single-note advertisement calls, three-note advertisement calls, and three-note aggressive calls all elicited increases in number of notes per minute, number of calls per minute, the frequency of multi-note calls, and the frequency of aggressive calls. Playbacks of aggressive calls evoked more aggressive calls in response than playbacks of advertisement calls, and the frequency of aggressive calls increased with increasing playback volume. The communication system of H. ebraccata, which is more complex than that of many frogs, apparently allows males to convey separate messages simultaneously to males and females.