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The Bottlenose Dolphin

Tursiops truncatus

Order: Cetartiodactyla

Suborder: Cetancodonta

Family: Delphinidae

Genus: Tursiops

Species: Tursiops truncatus (Montagu, 1821)

Name: Bottlenose dolphin, tursìope, delfín mular, grand dauphin, großer Tümmler.



The common bottlenose dolphin is a large, torpedo-shaped dolphin with a thickset, rounded head and short bottlenose-shaped beak. Their back is typically grey (although it can be found blackish or brow-grey) with lighter flanks and a white creamy belly. Their size can vary between 1.8 to 3.9m weighing up to 650 kg. Further, females can live between 20-50 years while males have a lifespan of about 20-40 years (Still et al., 2019).


The bottlenose dolphin can be found worldwide in temperate and tropical waters both inshore and out in the sea. They are also found near river estuaries, headlands and sandbanks where there are strong tidal currents. It is estimated that the global population is of 600.000 individuals while the population in the Mediterranean Sea is not known, yet estimated to be below the 10.000 individuals. It is interesting to note, that the Mediterranean population of bottlenose dolphins is genetically distinct from the North Atlantic Ocean or elsewhere (Still et al., 2019). This means, that the animals within the Mediterranean do not reproduce with animals of the Black Sea or the Atlantic Ocean.


The Mediterranean Sea is a place where dolphins have always captured the human imagination, a natural paradise where spotting dolphins from the coast and meeting them at sea was a normal event. All this has changed: thousands of dolphins were killed in the first half of the twentieth century as human perception had transformed them from mythical animals to competitors for fishing. Up until the 1960, the bottlenose dolphin was subject to human persecution in the Mediterranean Sea (Bearzi et al., 2004; IUCN, 2013). Dolphin extermination was promoted for at least a century by the governments of many Mediterranean countries, including Spain, France, Italy, the former Yugoslavia and Greece, including through money reward (Bearzi et al. 2004, Smith, 1995).


Currently, their main threats are incidental catches in fishing activities, chemical contamination, over-exploitation of coastal fish resources (Bearzi et al., 2009; IUCN, 2013), disturbance from leisure vessels, whale watching and nautical activities (jet-ski) as well as environmental degradation (UNEP, 2013).

The Mediterranean subpopulation has declined within the past decades and is now classified as Vulnerable (VU) on the IUCN Red List. Nevertheless, it is still possible to see these dolphins all year round in this Sea, especially in coastal waters. In the Mediterranean Sea the bottlenose dolphin is protected by the Bern Convention (1982, 2002), by the EU Habitat Directive adopted in 1992, the Barcelona Convention (1995, 2009 and 2012), CITES (2010) and, as all wildlife, by the Italian law n. 157/922.


Oceanomare Delphis Onlus is an Italian NGO that strives to study cetaceans in the Tyrrhenian Sea and also focuses on the common bottlenose dolphin in this area. They are currently working on two projects: The Ischia Dolphin Project (IDP) and the Delfini Capitolini (Roman Dolphin) (DC) project.


The Ischia Dolphin Project is focused on the communities of cetaceans that can be encountered in an area that covers about 8800 Km2 between the islands of Ischia, Ventotene, Ponza and the Italian mainland. One of their target species is the bottlenose dolphin. With 207 identified individuals since 2004, the results obtained support the hypothesis that the waters around Ischia Island represent a feeding area, as well as a calving and nursery area for the bottlenose dolphin local population. The study area of IDP includes a Marine Protected Area called ‘Regno de Nettuno’ with a specific section (Section D) dedicated to the conservation of cetaceans, in particular the common dolphin (Delphinus delphis). Furthermore, it has recently been recognized as an Important Marine Mammals Area (IMMA) by the IUCN, with common dolphin, bottlenose dolphin and fin whale as qualifying species. However, despite the severe anthropogenic pressure (overfishing, vessel traffic, pollution) in the area, no management actions aimed at preserving the local ecosystem are implemented until today.


The Delfini Capitolini (DC) project was born in 2010 to study the bottlenose dolphins along the coast in front of Rome, between the mouth of the Tiber and the Marine Protected Area ‘Secche di Tor Paterno’. Due to this research effort ODO researchers were able to detect the regular presence of this species in these waters. The data obtained with photo identification shows that there are around 130 individuals that frequent the area including females, juveniles, and newborns. The data collected in this project was used to create a density map that was then presented to the European Commission in the frame of the Habitat Directive of the European Union (Malta, 27-29 September 2016). This directive aims to establish Natura 2000 sites for marine species and habitats. Further, the effort paid off as the mouth of the Tiber received the status of Area of Interest (AoI) by the IUCN Marine Mammal Protected Areas Task Force. The further investigation on this AoI can in the future turn these waters into Important Marine Mamma Area (IMMA).


Last but not least, with the aim to assess the conservation status of the bottlenose dolphin in the Mediterranean Sea, ODO participated in the project TURSIOMED – coordinated by Fondazione Acquario di Genova and supported by ACCOBAMS. ODO submitted all data (routes, sighting coordinates, photographic material for photo-id analyses) gathered by Delfini Capitolini (2015-2016) and Ischia Dolphin Project (2004-2016) on the Internet platform (www.intercet.it), available to all international scientific community.


With the aim to keep the conservation effort alive and as well as including an outreach aspect, ODO created a volunteer based research station in the frame of the Ischia Dolphin projects. If you would like to join their activity and learn more about the bottlenose dolphin and other cetaceans in the area make sure to check out our webpage and get in contact with us. We would be thrilled to have you on board and make this an educational and fun experience.


References:

CITES or Washington Convention protects the trade of Tursiops truncatus aduncus, the subspecies from the Black Sea: https://speciesplus.net/#/taxon_concepts/7086/legal

Bearzi, G., Fortuna, C.M., Reeves, R.R. (2009), Ecology, behaviour and conservation of Common Bottlenose Dolphins Tursiops truncatus in the Mediterranean Sea. Mammal Review n.39(2): pp. 92-123

Bearzi, G., Holcer, D., Notarbartolo di Sciara, G. (2004), The role of historical dolphin takes and habitat degradation in shaping the present status of northern Adriatic cetaceans. Aquatic Conservation: Marine and Freshwater n.14: pp. 363-379

IUCN (2013) Tursiops truncatus. http://www.iucn.it/scheda.php?id=-1062271328

Smith T.D. 1995. Interactions between marine mammals and fisheries: an unresolved problem for fisheries research. Pp. 527–536 in A.S. Blix, L. Walløe, Ø. Ulltang, eds. Whales, Seals, Fish and Man. Elsevier Science, Amsterdam.             

Still, R., Harrop, H., Stenton, T. And Dias, L. (2019). Europe’s sea mammals. A field guide to the whales, dolphins, porpoises and seals. Wild Guides Ltd., Hampshire, UK.

UNEP-MAP-RAC/SPA (2013). Important areas for the conservation of cetaceans in the gulf of lions shelf and slope area: synthesis of existing data on cetaceans and threats. By David, L., Di Méglio, N. Ed. RAC/SPA, Tunis, 37 pp.

WORMS: World Register of Marine Species. Tursiops truncatus classification: http://www.marinespecies.org/aphia.php?p=taxdetails&id=137111

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