Can whistles be used to estimate dolphin abundance?

Abstract

Dolphin whistles have been studied extensively for both wild and captive animals. They are used in the communication between individuals, to maintain contact within individuals of a herd, and to coordinate herd movements. However, little is still known on how whistles can be used to ascribe individuals. Therefore, the present study is focused on determining the stereotypy of the most frequently emitted whistles by captive bottlenose dolphins,Tursiops truncatus, housed in two different marine parks. Stereotypy was computed by changing the similarity index while classifying whistles into whistle types using Matlab BELUGA and ArtWARP. Signature whistles are an individual distinction and have a similarity index greater than 95%, therefore, allowing to assess the minimum number of whistling dolphins in a pod that emit signature whistles. This is specially important in the wild, where in some occasions, it is very difficult to assess how many individuals are present. Thus this very simple method will be useful to quantify the number of signature whistles from underwater recordings, and to relate it with the possible number of dolphins present. It is necessary to implement methods like this one to better understand how dolphins are using whistles, since acoustic communication is the most important sense in dolphin species. [Work supported by PAPIIT&PASPA-UNAM.]