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.
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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.
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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.Jensen@gmail.com
Web: www.marinebioacoustics.com