Vocal behavior of the Ponmudi Bush Frog (Raorchestes graminirupes): Repertoire and individual variation

Frogs and toads have species-specific repertoires of vocalizations that function in contexts related to reproduction. Although some 6000 anuran species have been described to date, we have comparatively few descriptions of their vocalizations, which are among their most conspicuous behaviors. Statistical descriptions of vocal repertoires are key to understanding the evolution of frog communication systems and play potentially important roles in anuran conservation and systematics. The primary objective of this study was to describe the vocal repertoire and calling behavior of the Ponmudi Bush Frog, Raorchestes graminirupes, a recently described species endemic to the Western Ghats of India. A secondary objective was to investigate patterns of individual variation in calling behavior and several potential sources of that variability, including temperature, body size, and physical condition. We analyzed 1000 calls from 25 males near Ponmudi in the State of Kerala. Males produced two distinct, pulsatile call types that were temporally organized in a hierarchical structure of short call groups and longer call bouts. The two call types differed primarily in call duration, amplitude envelope, and the number of pulses per call. The dominant frequency of both call types was significantly negatively correlated with body length, mass, and condition. Temporal properties were generally unrelated to male phenotype, and few call properties were related to temperature in our sample of recordings. Based on coefficients of variation (CV), dominant frequency exhibited less variability within and among individuals (CV ≤ 4%) compared with temporal properties (e.g., 10% < CVs < 30%). We discuss these results in relation to previous studies of vocal repertoires and call variability in other anurans.