Signature whistle variations in a bottlenosed dolphin, Tursiops truncatus

To examine whether context-specific information is superimposed upon the individual cues present in the whistling of the bottlenosed dolphin, Tursiops truncatus, parameter variations within the two most frequently emitted whistle types of a captive individual were investigated in three different behavioural contexts. The study concentrated on comparing signal features of spontaneously occurring vocalizations in two possible phases following the performance of a trained discrimination task and those occurring during isolation. Phases of the discrimination task differed according to whether the animal showed ''correct'' (reward given) or ''incorrect'' performance (no reward). Signature whistles were most common in isolation, but also represented just over half of the whistles following a choice task. Of 14 signature whistle frequency and time parameters measured 9 differed significantly between isolation and at least one of the phases following a choice task (Table 1). Three parameters also varied according to whether performance was correct or incorrect. In contrast, only one out of four parameters (start frequency) measured from the second most frequent whistle type varied significantly between contexts (isolation vs. phase following correct choice). The results indicate that not only identity but also context-related information is available in the whistles of a bottlenosed dolphin.