Development of Tursiops truncatus Sonar System During First Months of Life in Captivity: Acoustic Interactions with other Community Members

The aims of the present work are to point out the time necessary for a calf to learn the use of biosonar, the role played by the mother and the other community members in the learning process, and the possible acoustical changes of the community after the entry of a new calf. The Delphinaria of Cattolica and Rimini house two small communities of bottlenose dolphin. The births of Daphne and Blue in autumn 1992 and spring 1997, respectively, offered suitable conditions to carry this study. The sonar signals emitted by the dolphins were collected systematically using a Brüel&Kjær 8105 hydrophone. All the data were processed using MATLAB software m-file language and analyzing statistical and acoustic parameters. The results show that all members of both communities dynamically participated in the calves' learning phase and their acoustic behavior was affected by the presence of the new entries. After several months the calves play a central role within the communities and the other members tend to modify the acoustic features of their biosonar adapting it to that of the calves. On the other hand, the calves seem to be acoustically similar to the other juveniles of the communities.