Geographic variation in whistles produced by short-beaked common dolphins (Delphinus delphis) in the Mediterranean Sea and Atlantic Ocean

Acoustic features of whistles produced by short-beaked common dolphins were investigated in two adjacent macro geographic areas: Atlantic Ocean (221 high quality sounds used for the analyses) and Mediterranean Sea (193 high quality sounds used for the analyses).Twelve parameters were measured from each whistle: duration, beginning, end, minimum and maximum frequency, frequency range, beginning and ending slope, inflection points, steps, number of minima in the contour, number of maxima in the contour. Modulation parameters showed the highest coefficients of variation and were the most varying factors within the areas. Comparing data among basins (nonparametric Mann-Witney and Kolmogorov- Smirnov tests), differences were significant for duration and all frequency parameters except for minimum frequency. The Discriminant analysis can be used to predict basin’s sounds with 72.5% accuracy. Results are in agreement with the hypothesis proposed by previous genetic studies that two distinct populations with a low gene flow between the basins are present. However intra basin differences leave open the issue of local adaptation to specific habitat conditions.