Online

Rege-Colt, Manali

Biology

2022

M.S.

The pantropical spotted dolphin in the Eastern Tropical Pacific (ETP) is found in two genetically and phenotypically distinct ecotypes, coastal and offshore. These habitats have distinct acoustic characteristics and sound fields, which can lead to the evolution of distinct acoustic communication. Whistles are tonal sounds widely used by dolphins as they mediate species and individual recognition and social interactions. Here we study the intraspecific variation of pantropical spotted dolphin ecotypes in their whistle acoustic structure and repertoire. To compare spotted dolphin whistle repertoires, we used recordings obtained from boat-surveys throughout the species distribution in the ETP. Random forest classification performed with an accuracy of 83.99% and identified duration and peak and minimum frequency as most informative in distinguishing between ecotypes. Overall, coastal spotted dolphins produced whistles that were shorter in duration and lower in frequency than offshore dolphins. Ecotypes produced whistle repertoires that were similar in diversity, but different in contour composition, with the coastal ecotype producing 'simpler' whistles than offshore dolphins. The results of this study suggest that acoustic adaptations to coastal and offshore environments are important contributors to intraspecific variation of dolphin whistle repertoires.