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A quantitative study of the behaviour of captive Bottlenose Dolphins (Tursiops truncatus)

Rhind, Susan (1991) A quantitative study of the behaviour of captive Bottlenose Dolphins (Tursiops truncatus). Honours thesis, Murdoch University.

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Focal animal sampling (Altmann 1974) was used to gather quantitative data, over a period of 6 months, on associations and interactive behaviours of captive bottlenose dolphins (Tursiops truncatus ). The focal animals consisted of three adult females and three, two year old calves who belonged to a group of nine dolphins. Associations between the animals were assessed using proximity measures and the behaviour of synchronous surfacing between animals. Resulting data showed strong associations between mothers and calves and between one adult female and male. Group instability was revealed by the progressive development of two subgroups within the captive colony. The division between these subgroups became more pronounced with time and ended with the establishment of an alliance between two previously unassociated males. These males attacked the female who had been associating with the male, and she died some days later. Following this event, group stability returned and animals from both subgroups were recorded as interacting more frequently. This was most evident among the calves who previously had not socialised with each other to any degree. At this same time, there was an abrupt change in the swimming position that the calves had previously adopted with their mothers. Interactive and social behaviours between the animals were recorded to identify the nature of relationships between animals. Most of these behaviours were relatively infrequent. However, several trends were apparent. Firstly, the males and females (excluding the male-female pair) rarely interacted socially. Likewise, there were almost no social interactions between the adult females. Of those interactive behaviours documented between the males and females/calves, the males were shown to consistently initiate most interactions. Unlike the adults, the calves were highly sociable and interacted frequently with each other and with their mothers. Over time, the calves associated less with their mothers and socialised more with each other. Assessment of responsibility in maintaining proximity was carried out by recording approaches and leaves between dyads. The results from this data showed that the calves associated with each other in a reciprocal manner. Between the mother-calf pairs, the mothers were initially shown to be responsible for maintaining close proximity with their calves. However the level of such maintenance decreased with time. A variety of general behaviours was documented in order to assess activity budget, and it was shown that adult females rested more than the calves and, in turn, the calves socialised and solicited attention more than the adults. Most of the observed changes in the behaviour of the calves during the course of the study were probably a consequence of the shifting group dynamics, rather than developmental changes due to maturation. The cause of the group instability was unknown, however, it is possible that the increasing sexual maturity of the males was a significant factor.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Bradley, Stuart
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