Quantitative analysis of tonal calls from five odontocele species, examining interspecific and intraspecific variation

Whistle vocalizations of five odontocete cetaceans, the fals killer whale P . crassidens, short-finned pilot whale G. macrorhynchus, long-finned pilot whale G. melas, white-beaked dolphin L. albirostris and Risso's dolphin G. griseus, were analysed and summarized quantitatively. Recordings were acqui red from a number of locations and encounters. significant differences were found between species and, to a lesser extent, between locations. The call s of the two pilot whale species are distinct despite their close relatedne ss, and similar size and morphology. This may be due to selection pressures to maintain distinctiveness. The variance was partitioned into between-spe cies, between-location (within species) and within-location factors. for th e frequency variables, variation between-species is high relative to variat ion between locations. Thus, geographic variation is a relatively minor eff ect, compared to the many processes which cause interspecific differences. The within-location component includes such factors as social context, beha viour and group composition. This component is of a similar magnitude to th e between-species component, indicating that whistles vary considerable wit h these factors. Significant between-location differences may be attributab le to these confounding factors. For whistle duration, most of the variatio n occurred within location. There is less significant variation in duration across species compared with the frequency measures. This study highlights the need to collet sample across all potential strata whenever possible, a nd provides a framework for future, more comprehensive work.