Geographic variation of whistles of the striped dolphin (Stenella coeruleoalba) within the Mediterranean Sea

Abstract

The striped dolphin is a cosmopolitan species distributed worldwide. Morphological and genetic studies strongly suggest that the Mediterranean and eastern North Atlantic populations are isolated from each other. The Mediterranean population is considered a distinct conservation unit by International Union for the Conservation of Nature experts, classified as "vulnerable." This study describes the geographical variation of the striped dolphin whistles within the Mediterranean Sea. Recordings were collected from 1996 to 2003 throughout the basin, employing multiple platforms. Thirty-seven independent sightings with acoustic data collection were made, and 599 whistles were extracted and considered for statistical analysis. Whistle analysis enabled the identification of sub-populations of striped dolphins within the Mediterranean Sea. The acoustic diversity observed reflects the genetic differences recently found among striped dolphins inhabiting different Mediterranean regions. The results of this study support the hypothesis that gene flow reduction plays an important role in determining variation in whistle duration and frequency parameters, while ecological and social factors influence parameters of the modulation domains. The ability to acoustically identify distinct geographic sub-populations could provide a useful tool for the management of this protected species.