Dear Colleagues:
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 :
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.
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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
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