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Papale E.,University of Turin | Azzolin M.,University of Turin | Cascao I.,University of The Azores | Gannier A.,Groupe de Recherche sur les Cetaces GREC | And 9 more authors.
Ethology Ecology and Evolution

Genetic studies have shown that there are small but significant differences between the short-beaked common dolphin populations in the Atlantic Ocean and those in the Mediterranean Sea. The short-beaked common dolphin is a highly vocal species with a wide sound production repertoire including whistles. Whistles are continuous, narrowband, frequency-modulated signals that can show geographic variation in dolphin species. This study tests whether the differences, highlighted by genetic studies, are recognisable in the acoustic features of short-beaked common dolphins whistles in the two adjacent areas of the Atlantic Ocean and the Mediterranean Sea. From a selected sample of good quality whistles (514 recorded in the Atlantic and 193 in the Mediterranean) 10 parameters of duration, frequency and frequency modulation were measured. Comparing data among basins, differences were found for duration and all frequency parameters except for minimum frequency. Modulation parameters showed the highest coefficient of variation. Through discriminant analysis we correctly assigned 75.7% of sounds to their basins. Furthermore, micro-geographic analysis revealed similarity between the sounds recorded around the Azores and the Canary archipelagos and between the Bay of Biscay and the Mediterranean Sea. Results are in agreement with the hypothesis proposed by previous genetic studies that two distinct populations are present, still supposing a gene flow between the basins. This study is the first to compare short-beaked common dolphins whistles of the Atlantic Ocean and the Mediterranean areas. © 2013 © 2013 Dipartimento di Biologia, Università di Firenze, Italia. Source

Papale E.,University of Turin | Azzolin M.,University of Turin | Cascao I.,University of The Azores | Gannier A.,Groupe de Recherche sur les Cetaces GREC | And 9 more authors.
Acta Ethologica

To improve our understanding of the complex genetic and ecological structure of bottlenose dolphin (Tursiops truncatus) populations, we examined the acoustic features of communication signals from two geographically contiguous areas: the Central-Eastern North Atlantic and the Mediterranean Sea. Variations in the whistles were evaluated for four locations. Ten signal parameters were measured and used to statistically differentiate between the areas. Over 79 % of sightings were correctly classified by discriminant function analysis, confirming an acoustic differentiation between the two basins. The results of cluster analysis using the mean values of the parameters for each sighting showed that the three easternmost sightings from the Mediterranean and one sighting from the Canary archipelago formed a separate cluster from the rest of the Atlantic. The two sightings from the Alboran Sea in the west Mediterranean were grouped with the Atlantic recordings. There was more variability in whistles from the Atlantic Ocean consistent with data from genetic and photo-identification studies that document resident and non-resident animals in the area. The results suggest that the Alboran area may be inhabited by animals differentiated from the rest of the Mediterranean basin as a result of habitat features. © 2013 Springer-Verlag Berlin Heidelberg and ISPA. Source

Papale E.,University of Turin | Papale E.,National Research Council Italy | Gamba M.,University of Turin | Perez-Gil M.,Society for the Study of Cetaceans in the Canary Archipelago SECAC | And 2 more authors.

An increase in ocean noise levels could interfere with acoustic communication of marine mammals. In this study we explored the effects of anthropogenic and natural noise on the acoustic properties of a dolphin communication signal, the whistle. A towed array with four elements was used to record environmental background noise and whistles of short-beaked common-, Atlantic spotted- and striped-dolphins in the Canaries archipelago. Four frequency parameters were measured from each whistle, while Sound Pressure Levels (SPL) of the background noise were measured at the central frequencies of seven one-third octave bands, from 5 to 20 kHz. Results show that dolphins increase the whistles ' frequency parameters with lower variability in the presence of anthropogenic noise, and increase the end frequency of their whistles when confronted with increasing natural noise. This study provides the first evidence that the synergy among SPLs has a role in shaping the whistles' structure of these three species, with respect to both natural and anthropogenic noise. © 2015 Papale et al. Source

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