CONICET | Buscador de Institutos y Recursos Humanos

Preliminary results have been obtained on the behaviour of Commerson´s solphins wich have recently been targeted by the dolphin-watching industry. Data were gathered at Bahía Engaño, northern Patagonia, between February 98 and June 99, from a 21m high cliff. Scan sampling methodology was applied every half an hour. Behaviour was classified as travelling, milling, co-operative feeding, resting, socialising or undefined. PhotoID was started in order to identify individuals and total size of the herd involved. Interactions with boats were also studied. Dolphins were sighted in 31 out of 147 scans. The mean group size was 2.12 individuals (SD=1,77), with a maximum of 20 individuals. The dolphins seem to display a daily pattern of movement, arriving to the area during the morning, being more abundant during noon and the first hours of the evening and moving away at dusk. The highest number of animals in the area was recorded between 12:00 and 16:00hs. The number of animals in the area also increased since February, reaching a peak in May. As far as known, these dolphins are in the study area during winter while during summer they are not. Behaviour scan samples were performed on 135 groups. The main activities were milling (36%) and travelling (31%), followed by socialising (10%), co-operative feeding (7%) and resting (6%). The undefined behaviours were also 10%. Birds were present and interacting with dolphins when feeding. By means of photo ID at least 22 dolphins were identified and some resigthted. The number of individuals in the area would be no less than 130 dolphins. Interactions with the boat were studied on board or from the cliff. On the base of the present information the dolphins seem to socialise often in the presence of the boat (1-80 individuals) and not all of them are involved in the interactions.

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