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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

Rendell L.,University of St. Andrews | Simiao S.,University of St. Andrews | Brotons J.M.,Direccio General de Medi Rural i Mari | Airoldi S.,Tethys Research Institute | And 2 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems

Sperm whales in the Mediterranean are classified as 'Endangered' by the IUCN. They are apparently isolated from adjacent Atlantic populations, and subject to anthropogenic pressures including interactions with illegal driftnet fisheries, ship strikes, ingestion of debris and underwater noise. Photo-identification data opportunistically collected from the western Mediterranean basin show that individual sperm whales regularly move in excess of 500km across the western basin, suggesting that this area is occupied by a single population. The best abundance estimate for this region is approximately 400 animals, with confidence intervals between 200 and 1000. Given the mortality levels reported in the literature, this figure suggests that the conservation status of sperm whales in this region is very serious. Immediate priority should be placed both on conducting systematic surveys for abundance estimation and on measures to reduce the mortality associated with driftnet fishing. © 2014 John Wiley & Sons, Ltd. Source

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