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| Azorean Species | Common Bottlenose dolphin – Tursiops truncatus – Golfinho-roaz



Scientific Name: Tursiops truncatus (Montagu, 1821).


Common Name (UK, FR, PT, ES, DE): Common bottlenose dolphin. Grand dauphin. Golfinho-roaz. Delfín mular. Hochcöplige tümmler. (Jefferson et al. 2015).


Short Species description: This cetacean belongs to the suborder of toothed whales (Odontoceti). This species is one of the best known as they are held captive around the world and appear on television and advertisements. Bottlenose dolphins have large dimensions and a relatively robust body. Calves are born with 1-1.3 m while adult length range from 1.9-3.8 m and have a maximum weight of 650 kg. Males are usually slightly larger than females. The color pattern of this dolphin is very widespread and differs from light gray to almost black on the sides and back. (Jefferson et al. 2015).


These dolphins feed mainly on fish and squid but can also eat shrimps and other crustaceans. Have a maximum longevity of 50 years for females and 45 years for males. (Jefferson et al. 2015).


Population status: Least Concern (overall species) by IUCN status. (Jefferson et al. 2015).


Occurrence in the Azores (including season): Resident in the Azores and are usually sighted in coastal areas near the islands. They can be observed interacting with the boats especially performing bow-riding. These dolphins may associate with individuals of different species as the common dolphin (Delphinus delphis), the striped dolphin (Stenella coeruleoalba) and the Atlantic spotted dolphin (Stenella frontalis). (Quérouil et al. 2008, Seabra et al. 2005, Jefferson et al. 2015).


Habitat Use: Mostly coastal areas and continental shelf waters but can also be found offshore. They are distributed in tropical and temperate areas of the world. In the Azores they tend to be found at depths less than 750 m. (Seabra et al. 2005, Jefferson et al. 2015).


Acoustics: They make clicks to determine the shape and location of adjacent elements, such as potential prey. Bottlenose dolphins also use sounds to communicate like whistles, squeaks and sounds made by body language. The whistles are narrow-band sounds and, in this species, its frequency spectrum varies between 0.8-28.5 kHz. (Gridley et al. 2015, Au et al. 1993).


Pod Size: Usually they are associated in small groups with less than 20 individuals, however, in some deeper areas large pods of several hundred can be observed. (Jefferson et al. 2015).


Typical Behaviour: They are very active animals especially when they feed and socialize. These dolphins usually perform aerial behaviors such as leaping, tail slapping and sometimes they ride in the waves caused by large whales. The pods are formed by gender, age, family bond and reproductive condition. (Augusto, Rachinas-Lopes & dos Santos, 2011, Jefferson et al. 2015).




References


Augusto, J.F., Rachinas-Lopes, P. & dos Santos, M.E. (2011). Social structure of the declining resident community of common bottlenose dolphins in the Sado Estuary, Portugal. Journal of the Marine Biological Association of the United Kingdom 92, pp. 1773–1782. doi:10.1017/s002531541100088.


Au, W.W.L (1993). The sonar of Dolphins. Springer-Verlag New York. ISBN 978-1-4612-4356-4.


Gridley, T., Nastasi, A., Kriesell, H.J. & Elwen, S.H. (2015) The acoustic repertoire of wild common bottlenose dolphins (Tursiops truncatus) in Walvis Bay, Namibia. Bioacoustics 24, pp. 153-174, doi: 10.1080/09524622.2015.1014851.


Jefferson, T.A., Webber, M.A., Pitman, R.L. (2015). Marine Mammals of the World; A Comprehensive Guide of Their Identification. 2nd edition. London: El Sevier.


Quérouil, S., Silva, M.A., Cascao, I., Magalhaes, S., Seabra, M.I., Machete, M.A. & Santos, R.S. (2008). Why do dolphins form mixed-species associations in the Azores? Ethology 114, pp. 1183-1194.


Seabra, M.I., Silva, M.A., Magalhães, S., Prieto, R., August, P., Vigness-Raposa, K., Lafon, V. & Santos, R.S. (2005) Distribution and habitat preferences of bottlenose dolphins and sperm whales with respect to physiographic and oceanographic factors in the waters around the Azores. Proceedings of the 19th Annual Conference of the European Cetacean Society. La Rochelle, France, pp. 105.