Abstract:
Vocalizations produced by a neonate male bottlenosed dolphin during the first 5 days after birth were compared to the vocalizations of two adult female bottlenosed dolphins housed in the same enclosure. Audio and video recordings were made of the focal mother and her calf from birth. Calf vocalizations were identified as sounds that occurred concurrently with the emission of bubble streams by the calf. Adult vocalizations were recorded prior to, during, and after the birth of the calf. Initial calf vocalizations were of a single sound type varying in duration from 0.35 to 1.4 s. The sounds produced by the calf were broadband signals with spectral energy from approximately 0.5 to 9 kHz and peak energy levels between 1.2 and 1.6 kHz. Spectrographic and aural analyses of sounds made by the calf and adults revealed that calf vocalizations were more similar to the burst-pulse sounds of both adults than to any other vocalizations of either dolphin. Evolution of the calf's sounds toward narrow-band frequency-modulated whistles was evident in later recordings. These results contrast with previous reports that bottlenosed dolphins produce whistles from birth and elucidate relationships between the production of whistles and burst-pulse sounds and their ontogeny.