Complexity index and proportional variability to study dolphin whistles

Abstract

Dolphin whistles are emitted especially during social interactions and feeding activities involving group cohesion, individual recognition and recruitment. This paper presents a new methodology to describe and compare the whistle repertoire of dolphins. It consists on first extracting the whistle contour using Matlab BELUGA, then classifying whistles into whistle types using Matlab ARTwarp, next classifying whistle types into four general categories (high complexity, low complexity, linear long, and linear short), and finally computing a complexity index and a proportional variability of the whistle repertoire. The method was tested with whistles from captive and wild bottlenose dolphins, Tursiops truncatus, and from wild Guiana dolphins, Sotalia guianensis. Results obtained showed that this very simple method is useful to describe the whistle repertoire and to compare it according to the activity of dolphins, and between species. It is necessary to implement new methodologies like this one to better understand how dolphins are using whistles, since acoustic communication is the most important sense in dolphin species. This is specially important in areas where dolphins are exposed to humans, and where underwater visibility is limited, like Laguna de Terminos, a Marine Protected Area in Mexico [work supported by PAPIIT-UNAM].