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Article Reference
Chambers S., James R. N. - Sonar termination as a cause of mass cetacean
strandings in Geographe Bay, south-western Australia. p.391-398, Acoustics
2005, Acoustics in a Changing Environment. Proceedings of the Annual
Conference of the Australian Acoustical Society, Busselton, Western
Australia. November 9 - 11, 2005
Title
Sonar termination as a cause of mass cetacean strandings in Geographe Bay,
south-western Australia
Abstract
Geographe Bay, south-western Australia has been host to several past mass
live cetacean (whale and dolphin) strandings. It is noticed that the
majority of stranded whales tend to be healthy, toothed cetaceans
(Odontoceti) which employ echolocation as a method of navigation. This paper
explores a bioacoustic mechanism known as sonar termination as a major
factor in the occurrence of these strandings in Geographe Bay. Sonar
termination occurs when a navigational echolocation click projected towards
the coast critically attenuates to a point where it is not detectable. The
paper proposes two mechanisms contributing to sonar termination: first, the
presence of a gently sloping shore and second, the presence of continuously
created stagnant micro sized bubbles (microbubbles). By depicting a wedge
shaped coastline as a perfect flat reflector the attenuative effect of
multiple reflections and resident microbubbles in a coastal water column on
a cetacean echolocation signal is calculated, and a limiting distance that a
cetacean may be able to detect the presence of a shoreline is determined
from these results. A brief review of the most recent mass strandings at
Dunsborough (03/04/05, 02/06/05) is presented and the plausibility of the
bioacoustic mechanism's role in the strandings is investigated.
Shane Chambers
Bioacoustics Research
Room 1.3
School of Physics
University of Western Australia
Tel: +61 8 64881335
email: <outbind://2/#>
URL: http://www.biophysics.uwa.edu.au/Bioacoustics <outbind://2/#>
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