Analysis of the sound emissions of captive bottlenose dolphins (Tursiops truncatus)

Abstract

Bottlenose dolphins (Tursiops truncatus) produce a great variety of sounds, including whistles, echolocation clicks, and other pulsed sounds. The behavior and the sound emissions of eight bottlenose dolphins were studied in a dolphinarium (Zoomarine, Albufeira, Portugal). Acoustic recordings were made with a B&K 8103 hydrophone and a Sony TCD-D10 Pro DAT recorder. Systematic behavioral observations were conducted (including show behaviors) simultaneously with acoustic recordings. Whistles were the most abundant signal type (n=4238) and several frequency modulation profiles were found to be repeatedly produced. Echolocation click trains and other pulsed signals were also produced. Whistle production throughout the day showed statistical concordance among 4 days of systematic sampling. Highest levels of whistle production occurred in interactions among the dolphins and in interactions between the dolphins and their trainers. The clicks and other pulsed sounds, more frequent in resting and swimming, showed a similar occurrence cycle throughout the day. Performances of conditioned behaviors (during shows) were associated with decreased levels of whistles and increased levels of click trains and other pulsed sounds.