Title and publication details:
Jensen, F. H., Beedholm, K., Wahlberg, M., Bejder, L., and Madsen, P. T. 2012. Estimated communication range and energetic cost of bottlenose dolphin whistles in a tropical habitat. Journal of the Acoustical Society of America. 131: 582-592.
Abstract and research conclusions:
Bottlenose dolphins depend on whistles for many aspects of their social behaviour, including maintaining group cohesion and recognizing familiar individuals. The amplitude and frequency of these whistles influence the range over which they can be heard by conspecifics. To study the source parameters of whistles from Bottlenose dolphins, Tursiops aduncus, we deployed a GPS-synchronized hydrophone array in Koombana Bay, Bunbury, Western Australia. Acoustic localization techniques were used to estimate the source level and energy content of individual whistles, and combined with noise and transmission loss measurements to estimate typical detection distances. Our study shows that bottlenose dolphins in Koombana Bay use lower source levels than reported for bottlenose dolphins in Moray Firth, Scotland, despite much higher noise levels in Koombana Bay. These two factors result in a general low communication range for dolphins here, and this might influence the structure and dispersion of groups and the contact between individuals. It seems unlikely that the low source levels is a result of high metabolic costs of whistling, as the acoustic energy in whistles, and the metabolic energy required to produce them, would be very low compared to the field metabolic rate of a normal bottlenose dolphin. Other ecological factors such as increased risk of being detected by predators, prey, or social competitors, are probably more important in shaping the acoustic behaviour of these animals.
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This study received support from the Danish Ph.D. School of Aquatic Sciences (SOAS), Aarhus University, DK, WWF Verdensnaturfonden and Aase & Ejnar Danielsens Foundation, the Siemens Foundation, the Faculty of Science at the University of Aarhus, DK, and the Danish Natural Science Foundation via a Steno scholarship and a logistics grant to PTM. Research was conducted under a permit to LB from the Department of Environment and Conservation and Ethics Approval from Murdoch University.