The following paper is now available online at JASA Express Letters;
full text is available at http://scitation.aip.org/journals/doc/JASMAN-ft/vol_125/iss_1/EL27_1-div0.html,
or by emailing me (Marla.Holt@noaa.gov):
Speaking up: Killer whales (Orcinus orca)
increase their call amplitude in response to vessel noise
Marla M. Holt, Dawn P. Noren, Val Veirs, Candice K. Emmons, and Scott
Veirs
Abstract:
This study investigated the effects of anthropogenic sound exposure on
the vocal behavior of free-ranging killer whales. Endangered Southern
Resident killer whales inhabit areas including the urban coastal waters
of Puget Sound near Seattle, WA, where anthropogenic sounds are
ubiquitous, particularly those from motorized vessels. A calibrated
recording system was used to measure killer whale call source levels
and background noise levels (1–40 kHz). Results show that whales
increased their call amplitude by 1 dB for every 1 dB increase in
background noise levels. Furthermore, nearby vessel counts were
positively correlated with these observed background noise levels.
©2009 Acoustical
Society of America
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__________________________________
Marla M. Holt, Ph.D.
NRC Postdoctoral Associate
Marine Mammal Program
NOAA/NMFS Northwest Fisheries Science Center
2725 Montlake Blvd East
Seattle, WA 98112
Phone: 206.860.3261
Fax: 206.860.3400
www.nwfsc.noaa.gov/research/divisions/cbd/marine_mammal/marinemammal.cfm