Imitative Behaviour By Indian Ocean Bottlenose Dolphins (t uRsiops Aduncus) in Captivity

Evidence is presented for the ability of Indian Ocean bottlenose dolphins (Tursiops aduncus) to learn complex behavioural sequences by observation and to imitate a wide variety of previously unfamiliar motor patterns and sounds, without any apparent external reinforcement apart from the performance of the activity itself, both in the presence and in the absence of the stimulus which originally evoked the imitative behaviour. The reproduction in fine detail by a dolphin of the comfort and sleeping movements of a Cape Fur Seal (Arctocephalus pusillus), leading to behavioural interactions between the two forms with attempts at copulation, and culminating in aggression is described. Further instances of observational learning are cited, including the imitation by dolphins of the activities and sounds of human divers during maintenance operations in the pool which resulted in elementary tool-using behaviour by the dolphins. Interactions between dolphins and seals occurred not only in captivity but also under free-ranging conditions. The significance of imitation in delphinids for comparative assessments of animal intelligence is discussed and the possible function under normal conditions of the delphinid faculty to imitate is considered. It is proposed that the tendency to imitate may be genetically programmed in delphinids to operate in the selection of compatible sexual partners, in the reinforcement of social bonds and in the strengthening of group cohesiveness.