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Behaviour of resident bottlenose dolphins (Tursiops truncatus) in Tramandaí river, South Brazil

2012Behaviour of resident bottlenose dolphins (Tursiops truncatus) in Tramandaí river, South Brazil.KLEINZ Solveig (Germany)solveig@kleinz.de
Organisation:University of Poitiers, Poitiers (FR) - Federal University of Rio Grande do Sul, Porto Alegre (Brazil)Supervisor :Freddie-Jeanne Richard (UP) & Ignacio Moreno (UFRGS)
Summary: Animals adapt their behaviour to the environment. Delphinids either form bands or schools, and forage solitary or in cooperation depending on the habitat, prey and circumstances. In an estuary in South Brazil we observed a resident group of bottlenose dolphins for four month during the high season of mullet occurrence. Overall, most of the time the animals were foraging, which suggest that they come to the estuary mainly to feed. Nevertheless, when prey was absent sometimes the dolphins stayed in the area milling around, socialising and waiting for fish to arrive. Especially one female with two calves was most often present. Reasons there for may be safety provided by the area and it may be more efficient to wait for mullet than to find prey in the open sea. The cooperation with the artisanal fishermen was most notably performed when high amount of mullet were in the channel. The number of dolphins involved in an association at one spot may depend on the size of schooling fish and their dispersal in the area. Furthermore, the social structure, the development of a lactating newborn and some aerial behaviour could be documented as well. For future research on this group, to fully understand their behaviour it is necessary to ascertaining how far they travel and what they do when they are not in the estuary. This could lead to a better understanding of dolphin behaviour, and in addition comparisons between populations at different places are possible.
Keywords:Bottlenose dolphins, Tursiops truncatus, behaviour, cooperative foraging,habitat use