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killer whale hearing range and seal transmitters (fwd)

Subject: killer whale hearing range and seal transmitters (fwd)
From: Dave Mellinger <>
Date: Mon, 22 Sep 2003 12:22:29 -0700
Date:    Thu, 18 Sep 2003 16:49:11 -0700
From: "Alejandro Frid" <[EMAIL PROTECTED]>
 I am considering using underwater sonic tags that ping at 80-100 kHz for
 studying diving behaviour of harbour seals in Alaska, but are concerned
 about artificially raising the seal's predation risk from transient killer
 whales (i.e.--orcas hearing and being attracted to the pingers).   The
 information I am aware comes from Szymanski et al. 1999 (J Acoust Soc Am
 106:1134-1141), and is that killer whale peak hearing sensitivity is at 20
 kHz, and tones of up to 120 kHz can be detected.  However, sensitivity
 declines gradually from above or below 20 kHz.
 Does anyone have information or an expert opinion suggesting whether a sonic
 tag transmitting at  80-100 kHz might artificially increase risk from orcas
 to the seals wearing the transmitters?  Suggestions for the lowest frequency
 that would be acceptable?
 The problem is that the higher the pinger's frequency, the lower the range
 from which we can detect it.  We tried transmitters pinging at 120 to 140
 kHz and their range was so small that we could not use them in the seal
 Thank you for your time,
 Alejandro Frid
 PhD Candidate
 Dept. Biological Sciences,
 Simon Fraser University

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