Abstract:

Bottlenose dolphins (Tursiops truncatus) produce individually distinctive signature whistles when they are in isolation. These whistles have been hypothesized to be important in individual recognition and group cohesion. However, captive individuals are known sometimes to imitate each other's signature whistles. Imitation could either lead to confusion over the caller's identity and act against individual recognition or could be used to address specific individuals in a communication network. In this study a hydrophone array with three transducers was used to investigate whether whistle copying also occurs in the wild. Recordings were made in a 500- m-wide channel in the Moray Firth, Scotland. Caller position was determined by comparing differences in the time of arrival of a sound at different hydrophones. Since signature whistles could not be determined by isolating individuals, exact whistle matching in vocal interactions was used to study copying. The results showed that whistle matching occurred in 17% of all whistle interactions. An analysis of the variability of matched whistles showed similar degrees of stereotypy as reported for signature whistles. Thus signature whistle matching seems to be an important feature of bottlenose dolphin communication in the wild. [This study was funded by a DAAD-Doktorandenstipendium HSPII/AUFE.]