Title: The acoustic repertoire of wild common bottlenose dolphins (<i>Tursiops truncatus</i>) in Walvis Bay, Namibia
Abstract: AbstractDescribing the repertoire of sounds produced by wild cetaceans is necessary for understanding their function, for acoustic population monitoring and for measuring the potential influence of anthropogenic impact. Geographic variation in the types and parameters of sounds makes regional assessment of vocal behaviour necessary. We describe the acoustic repertoire of a small population of common bottlenose dolphins (Tursiops truncatus) inhabiting Walvis Bay, Namibia from recordings made over 59 encounters (72 h) between 2009 and 2012. The characteristics of burst pulse (BP) sounds, low-frequency narrow-band (LFN) sounds, brays, whistles and chirps are described. The BP sounds identified were generated at 150–1050 pulses per second, and most were short, lasting less than 1 s in duration. Bottlenose dolphins from Walvis Bay produce the lowest frequency LFN sounds described for the species. Whistles ranged in frequency from 1.58 to 23.24 kHz, and the mean acoustic parameters were within the range of those described from other geographic regions. Chirps were identified infrequently and usually as single occurrences. Although several sound types were often produced in close temporal succession, we found little evidence of stereotyped bray production, even during recordings of animals feeding. Our results demonstrate geographic variation in both the characteristics and sound types used by bottlenose dolphins and highlight the importance of regional data collection as a pre-curser to passive acoustic monitoring programmes.Keywords:: bottlenose dolphinTursiops truncatuslow-frequency narrow-bandburst pulsewhistleNamibia AcknowledgementsThis publication is an output from the Namibian Dolphin Project. We are grateful to the interns of Oceans Research for their help collecting these data and particularly X. Indurkhya and N. Tonachella for their enthusiasm. We would like to thank Prof R. Millar and Prof M. Bester for support through the University of Pretoria Mammal Research Institute. Research was conducted with permission from the Namibian Ministry of Fisheries and Marine Resources, and we thank Dr J-P Roux for his support throughout our research activities.Disclosure statementNo potential conflict of interest was reported by the authors.Notes1. Email: [email protected]. Email: [email protected]. Email: [email protected] informationFundingTG was funded during the initial stages of this work by NERC PhD studentship, a University of St. Andrews Russell Trust Award and later the University of Pretoria Vice Chancellor's Postdoctoral fellowship. A scholarship from Sapienza University of Rome provided financial support to AN and postdoctoral fellowships from the University of Pretoria and Claude Leon Foundation provided assistance to SE. Equipment and running costs were provided by Idea Wild Fund, Prof V. Janik, and the Nedbank Go Green Fund.