[MARMAM] Recent paper on echolocation in Irrawaddy dolphins and Ganges river dolphins

Frants Jensen frants.jensen at gmail.com
Thu Apr 4 08:40:53 PDT 2013

Dear colleagues,

I am pleased to announce the publication of the following paper in the
journal PLOS ONE:

Jensen FH, Rocco A, Mansur RM, Smith BD, Janik VM, Madsen PT (2013):
*"Clicking in Shallow Rivers: Short-Range Echolocation of Irrawaddy and
  Ganges River Dolphins in a Shallow, Acoustically Complex Habitat"*.
PLOS ONE 8(4): e59284. doi:10.1371/journal.pone.0059284

The paper is open-access and can be downloaded at the following link:

*Abstract: *
Toothed whales (*Cetacea, odontoceti*) use biosonar to navigate their
environment and to find and catch prey. All studied toothed whale species
have evolved highly directional, high-amplitude ultrasonic clicks suited
for long-range echolocation of prey in open water. Little is known about
the biosonar signals of toothed whale species inhabiting freshwater
habitats such as endangered river dolphins. To address the evolutionary
pressures shaping the echolocation signal parameters of non-marine toothed
whales, we investigated the biosonar source parameters of Ganges river
dolphins (*Platanista gangetica gangetica*) and Irrawaddy dolphins (*Orcaella
brevirostris*) within the river systems of the Sundarban mangrove forest.
Both Ganges and Irrawaddy dolphins produced echolocation clicks with a high
repetition rate and low source level compared to marine species. Irrawaddy
dolphins, inhabiting coastal and riverine habitats, produced a mean source
level of 195 dB (max 203 dB) re 1 µPapp whereas Ganges river dolphins,
living exclusively upriver, produced a mean source level of 184 dB (max
191) re 1 µPapp. These source levels are 1–2 orders of magnitude lower than
those of similar sized marine delphinids and may reflect an adaptation to a
shallow, acoustically complex freshwater habitat with high reverberation
and acoustic clutter. The centroid frequency of Ganges river dolphin clicks
are an octave lower than predicted from scaling, but with an estimated
beamwidth comparable to that of porpoises. The unique bony maxillary crests
found in the Platanista forehead may help achieve a higher directionality
than expected using clicks nearly an octave lower than similar sized

I hope you may find the paper interesting. Feel free to contact me for any
Frants H. Jensen
Frants Havmand Jensen,
Danish Council for Independent Research, Natural Sciences Postdoctoral
Woods Hole Oceanographic Institution, MA, USA
Phone: (+1) 508 524 8436
Email: Frants.Jensen at gmail.com
Web: http://www.whoi.edu/profile.do?id=fjensen
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