Friday Harbor, Wa. -- A new research paper published by researchers working closely with The Whale Museum

shows that the endangered killer whales of Puget Sound raise their voices in direct proportion with increasing

underwater noise; that increasing underwater noise correlates with increasing numbers of vessels in the

neighborhood of the whales.

This past fall, seven of these endangered killer whales went missing, presumed dead, leaving a total population

of about 83 animals. On an average summer day approximately 20 vessels are near the whales throughout the

daylight hours. It is not uncommon to find 50 vessels surrounding these whales during summer weekends and

holidays.

The Southern Resident orcas' underwater vocalizations were recorded with an array of hydrophones. The

recorded data were used to calculate how much energy vocalizers put into each of their calls. In addition, the

number of vessels within 1000m of the research boat were counted. This is the first report of killer whales

responding to increased noise by increasing the volume of their calls, an effect called the Lombard effect, that

we humans are familiar with as we also raise our voices in noisy situations.

This paper concludes: "The potential costs of such vocal compensation are important to consider. For example,

increasing vocal output to compensate for noise might have energetic costs, lead to increased stress levels, or

degrade communication among individuals which could affect their activity budget. At some level, background

noise could also completely impede the use of calls by killer whales for communicative functions."

Supplementary information: research paper “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

JASA Express Letters

Published Online 22 December 2008

Journal of the Acoustical Society of America 125, 1 January 2009

Two graphs that summarize the principle findings:

A. Orca's calls' energy (termed Call Source Level) increases as Background Noise increases. For each decibel

of increase in background noise, the orca raise their voices by 1 decibel.

B. Background Noise increases of the Number of Vessels near the whales increases, here expressed as the

logarithm of the number of vessels within 1000 m of the research vessel.

In partnership with NOAA/NMFS, Beam Reach, OrcaSound, and others, The Whale Museum operates the

Seasound Hydrophone Network with five hydrophones deployed throughout the Salish Sea region.

Contacts: Jenny Atkinson (360) 378-4710 ext. 26 Executive Director, The Whale Museum

Val Veirs (360) 378-8360 Author and Whale Museum Board President

Marla Holt (831) 239-7277 Author and NOAA researcher

Scott Veirs (206) 251-5554 Author and Beam Reach researcher

Download a PDF of the release here.

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