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Comportamento spaziale di Tursiops truncatus lungo la costa del Mar Ligure: risultati preliminari
Abstract
Introduzione – Il Delfinide Tursiops truncatus (Montagu, 1821) è noto come specie cosmopolita dalle abitudini prevalentemente costiere (Cagnolaro et al., 1983; Notarbartolo di Sciara e Demma, 1994). Alcuni autori indicano l'esistenza di due ecotipi distinti, uno con abitudini propriamente costiere ed uno pelagico (Duffield et al., 1983). L'habitat d'elezione di questa specie lungo la costa italiana sembra essere compreso entro l'isobata dei 100 m (Gnone et al., 2005). T. truncatus è descritta come specie territoriale, ma le informazioni riguardo al suo home range sono frammentarie e spesso contraddittorie (Notarbartolo di Sciara e Demma, 1994). Materiali e metodi – Dati fotografici per l'identificazione di individui di T. truncatus attraverso marcaggi naturali della pinna dorsale sono stati raccolti in 4 aree della costa ligure e toscana: Imperia-Alassio (Istituto Tethys), Genova, La Spezia (Acquario di Genova), Viareggio (Centro CETUS). I dati sono stati raccolti tra il 1999 e il 2005, nel corso di osservazioni da imbarcazioni a motore e motor-sailer. Ciascuna immagine fotografica è stata associata al punto geografico di avvistamento. Risultati – La raccolta dei dati fotografici ha portato all'elaborazione di 4 cataloghi distinti per un totale di 212 individui foto-identificati. I cataloghi sono stati successivamente messi a confronto per rilevare eventuali riavvistamenti di individui. I risultati sono riassunti in Tab. 1 e Fig. 1.
... Bottlenose dolphins have been reliably reported along the coast of the entire Mediterranean Basin (Bearzi et al., 2008) and occur regularly around many of the region's offshore islands and archipelagos. They can also be encountered along continental shelf and shallow plateau waters (Notarbartolo Di Sciara et al., 1993;Bearzi et al., 2004;Ben Naceur et al., 2004;Gómez de Segura et al., 2006;Gannier, 2005;Gnone et al., 2006;Azzellino et al., 2008;Bearzi et al., 2008). Despite the widespread distribution of the species in the Basin, most of the research in the western Mediterranean Sea has been carried out on easily accessible populations (Bearzi et al., 2012), where the logistics of the studies (i.e. ...
... Movements within and across pelagic waters may occur as documented for some sectors of the Mediterranean Sea (e.g. Dhermain et al., 1999;Gnone et al., 2006). Nonetheless, no bottlenose dolphins were observed in the pelagic waters of the study area, confirming similar results obtained by Forcada et al. (1995) and Lauriano et al. (2010) for the Pelagos Sanctuary. ...
... 157/'92, requiring the designation of Special Areas of Conservation (SACs). The presence and distribution of bottlenose dolphins inside the Pelagos Sanctuary (a Specially Protected Area of Mediterranean Importance (SPAMI) located in the North Western Mediterranean Sea, for the conservation of cetaceans, see below) has been extensively studied on both a large scale (Gnone et al., 2011;Fiori, 2014, Gnone et al., 2022) and locally in several regions: France (Di-Méglio et al., 2015;Gannier, 2005;Labach et al., 2019), the Eastern Ligurian coast (Alessi et al., 2019;Gnone et al., 2006), Tuscany and the Tuscan Archipelagos , the West and South coast of Corsica (Dhermain and Cesarini 2007;Di-Méglio et al., 2015), and the North coast of Sardinia (Fozzi et al., 2001;Lauriano et al., 2003). Despite the significant research effort in the Pelagos Sanctuary, bottlenose dolphins have been only sporadically reported inside the study area, on the West coast of Liguria Bearzi et al., 2008) and their abundance and population dynamics are poorly known. ...
This study represents the first complete assessment of the population dynamics and residency of common bottlenose dolphins in the Western Ligurian Sea, an area where bottlenose dolphin sightings have been rare in the past. Despite being greatly affected by human pressure, information about this population is poor and sporadic. The study took place from April 2018 to December 2020. One hundred and seventy-one dedicated boat surveys were performed year-round resulting in 95 sightings, and 123 individuals were identified through mark-recapture photo-identification techniques. Dolphins were found to be present year-round. Most of the animals (79) used the area sporadically and only 19.5% of the dolphins (24) were seen regularly. Bottlenose dolphin abundance was estimated at 248 using open POPAN population models (CI 95% = 217-284). These results help fill a knowledge gap by highlighting the regular presence of bottlenose dolphins in the study area. Moreover, they represent a baseline for future studies investigating abundance trends and the conservation status of this population
... INTRODUCTION Despite the bottlenose dolphin (Tursiops truncatus) seems to be the most common species in the Eastern Ligurian Sea costal waters (Gnone et al., 2006), little is known about the social behaviour of this specie in the area. Bottlenose dolphins are described like social animals extremely interactive with other members of its own species so to have a classifiable society (Lusseau et al., 2005). ...
AIM – This study investigates the association patterns between individuals and the social habits of the bottlenose dolphin in the Eastern Ligurian Sea.
... An individual photo-identified off northern Corsica was resighted after 50 days in the Hyères Archipelago, southeastern continental France, 228 km away from the original location (Dhermain et al. 1999). Mid-range movements were also observed among bottlenose dolphins photo-identified off the northwestern coast of Italy, between Genoa and Viareggio, with five individuals resighted 100–130 km apart (Gnone et al. 2006). So far, the longest movement reported in the region is that of the solitary dolphin mentioned previously (400 km; Lockyer and Müller 2003). ...
While bottlenose dolphins in Mediterranean waters often display a high degree of site fidelity, movements across distant areas can occur. Such movements have important implications in terms of population viability, particularly in basins with low bottlenose dolphin densities. We report movements of nine individuals photo-identified up to 265km apart in western Greece. Four showed a certain degree of site fidelity to one area across several years, but were also found elsewhere, with two individuals moving between two areas. This study provides further evidence that animals appearing to be “resident” within a given area can temporarily leave and range widely.
KeywordsCommon bottlenose dolphin–
Tursiops truncatus
–Ecology–Movements–Mediterranean Sea
– Analysis of the presence of the bottlenose dolphin (Tursiops truncatus) along the Italian peninsula in relation to the bathymetry of the coastal band
- Gnone G Caltavuturo
- G Tomasini A
- V Zavatta
- Nobili A
GNONE G., CALTAVUTURO G., TOMASINI A., ZAVATTA V., NOBILI A. (2005) – Analysis of the presence of the bottlenose dolphin (Tursiops truncatus) along the Italian peninsula in relation to the bathymetry of the coastal band. Atti Soc. It. Sci. nat. Museo civ. Stor. Nat Milano, 146 (1): 39-48.