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
study.
Thank you for your time,
Alejandro Frid
PhD Candidate
Dept. Biological Sciences,
Simon Fraser University
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