Geographic variations in the whistle repertoire of Hawaiian spinner dolphins (Stenella longirostris)

Abstract

Studying geographic variations in the whistle repertoire of Hawaiian spinner dolphins (Stenella longirostris) will increase our understanding of the population structure of this species. In the present work, groups of spinner dolphins off the Islands of Oahu, Lanai, and Hawaii, were studied. The dolphin whistle repertoire of each island was used to search for geographic variations. Two methods were used: (1) spectrogram information extraction and (2) zero crossing. For the first method, frequency and time information was extracted from the spectrogram of each whistle. Results show that geographic variations exist in the whistle repertoire of Hawaiian spinner dolphins. Statistically significant differences were obtained by using discriminant function analysis: Wilks lambda=0.576; F(22,1866)=26.93, p<0.00001, N(Oahu)=314, N(Lanai)=293, and N(Hawaii)=339. Greater differences were found between the Oahu and Hawaii groups (3.413), intermediate differences were found between the Oahu and Lanai groups (2.200), and Lanai and Hawaii were the least different groups (0.560). These results indicate that looking for geographic variations in the whistle repertoire will help us in understanding the population structure of Hawaiian spinner dolphins. The results of the zero-crossing method will be compared to the spectrogram information extraction results. [Work supported by Leonida Memorial Scholarship, UH Seed Money Grant, UH Foundation Grant, Fulbright-GarcaRobles-CONACyT and DGAPA.]