Quantitative description of the vocal repertoire of the territorial olive frog, Babina adenopleura, from Taiwan

Anurans communicate using a repertoire of acoustic signals that can be classified as different call types based on differences in both their acoustic properties and the contexts in which they are produced. Descriptions of these repertoires represent a key first step towards understanding the vocal behaviour of any species and provide a critical foundation for comparative bioacoustic studies. In this study of the olive frog, Babina (formerly Rana) adenopleura, a territorial species from subtropical Taiwan, we used focal observations, acoustic recordings and statistical analyses of temporal, spectral and amplitude-related call properties to describe six different call types in the species' vocal repertoire. These call types included a putative advertisement call, territorial call, encounter call, amplectant call, distress call and alarm call. Advertisement calls consisted of four to five discrete notes, and they were the most commonly produced call. Territorial and encounter calls were delivered during interactions with other males; the former is a two-note call, whereas the latter is a distinctly pulsatile signal. Amplectant calls were acoustically similar to territorial calls but were delivered while males were in amplexus. Distress calls were given while the animal was being consumed by a snake, and alarm calls were recorded in response to startling stimuli. With basic descriptions of these call types in hand, we discuss several testable hypotheses for their putative adaptive functions.