Dear colleagues, I am pleased to announce the publication of the following paper in the Journal of the acoustical society of America:
*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," J Acoust Soc Am 131, 582-592. URL: http://link.aip.org/link/?JAS/131/582 DOI: 10.1121/1.3662067 *Abstract: * Bottlenose dolphins (*Tursiops* sp.) depend on frequency-modulated whistles for many aspects of their social behavior, including group cohesion and recognition of familiar individuals. Vocalization amplitude and frequency influences communication range and may be shaped by many ecological and physiological factors including energetic costs. Here, a calibrated GPS-synchronized hydrophone array was used to record the whistles of bottlenose dolphins in a tropical shallow-water environment with high ambient noise levels. Acoustic localization techniques were used to estimate the source levels and energy content of individual whistles. Bottlenose dolphins produced whistles with mean source levels of 146.7±6.2 dB re. 1 μPa(RMS). These were lower than source levels estimated for a population inhabiting the quieter Moray Firth, indicating that dolphins do not necessarily compensate for the high noise levels found in noisy tropical habitats by increasing their source level. Combined with measured transmission loss and noise levels, these source levels provided estimated median communication ranges of 750 m and maximum communication ranges up to 5740 m. Whistles contained less than 17 mJ of acoustic energy, showing that the energetic cost of whistling is small compared to the high metabolic rate of these aquatic mammals, and unlikely to limit the vocal activity of toothed whales. ------------------------------------------------------ Also, the following publication investigating sound production at depth for deep-diving pilot whales recently appeared in print in proceedings of the royal society of London B: *Jensen, F. H., Marrero Perez, J., Johnson, M., Aguilar Soto, N., and Madsen, P. T. (2011). * "Calling under pressure: short-finned pilot whales make social calls during deep foraging dives," Proc R Soc Lond B 278, 3017-3025 URL: http://rspb.royalsocietypublishing.org/cgi/content/abstract/278/1721/3017 *Abstract:* Toothed whales rely on sound to echolocate prey and communicate with conspecifics, but little is known about how extreme pressure affects pneumatic sound production in deep-diving species with a limited air supply. The short-finned pilot whale (*Globicephala macrorhynchus*) is a highly social species among the deep-diving toothed whales, in which individuals socialize at the surface but leave their social group in pursuit of prey at depths of up to 1000 m. To investigate if these animals communicate acoustically at depth and test whether hydrostatic pressure affects communication signals, acoustic DTAGs logging sound, depth and orientation were attached to 12 pilot whales. Tagged whales produced tonal calls during deep foraging dives at depths of up to 800 m. Mean call output and duration decreased with depth despite the increased distance to conspecifics at the surface. This shows that the energy content of calls is lower at depths where lungs are collapsed and where the air volume available for sound generation is limited by ambient pressure. Frequency content was unaffected, providing a possible cue for group or species identification of diving whales. Social calls may be important to maintain social ties for foraging animals, but may be impacted adversely by vessel noise. ----------------------------------------------------- I hope you may find the papers interesting. Please feel free to contact me for PDF versions. Best regards, Frants H. Jensen -- Frants Havmand Jensen, Danish Council for Independent Research, Natural Sciences Postdoctoral Fellow, Woods Hole Oceanographic Institution, MA, USA Phone: (+1) 508 524 8436 Email: frants.jen...@gmail.com Web: www.marinebioacoustics.com
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