Info: Whale communications/ dolphin pictures

Michael Williamson (whe_william@flo.org)
Mon, 5 Mar 1995 21:23:34

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Date: Sun, 05 Mar 1995 21:08:46 -0500 (EST)
From: Michael Williamson <WHE_WILLIAM@FLO.ORG>
Subject: Info: Whale communications/ dolphin pictures
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From:	SMTP%"MARMAM@UVVM.BITNET"  5-MAR-1995 15:25:23.77
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Subj:	Re: Whale communications/ dolphin pictures
 
Date:         Mon, 6 Mar 1995 07:22:22 GMT+1200
Reply-To:     Marine Mammals Research and Conservation Discussion
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              <MARMAM@UVVM.BITNET>
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From:         "Dr. David Helweg" <da.helweg@auckland.ac.nz>
Subject:      Re: Whale communications/ dolphin pictures
To:           Multiple recipients of list MARMAM <MARMAM@UVVM.BITNET>
 
> Your idea of dolphins transmitting information about images they perceive
>  from echolocation signals seems more plausible, but how to test it?  Dolphin
> echolcation signals essentially sound like clatter or clicking - not much
 there
> that resembles a "picture".  Keep in mind that these animals have very sophis-
> ticated acoustic processing capabilities.  Much of which is not understood
> and far beyond anything we are yet capable of emulating (as far as I know.)
 
I agree with Tom's statements both about whale song _and_
dolphin echolocation.  Re the casual conversation about
"whale echolocation," there is no evidence of *baleen*
whale echolocation.  Echolocation has been demonstrated
only in odontocetes.  Moreover, there is absolutely no
evidence that echolocating animals represent echoic
information visually, ie, that echolocating animals form
"sound pictures."  Recent experiments have shown that
echolocating dolphins can match objects experienced in
different sensory modalities, and that they can match
objects at different orientations.  Echolocating bats have
extremely acute temporal resolution abilities, and may
therefore "listen to details within echoes," but again it
does not follow from this that bats form spatial
representations of ensonified objects.
 
Dolphin echolocation signals sound like
clicks -- to us.  However,  with the dolphin's better high
frequency hearing, the clicks may "stretch" out in time and
provide a detailed signal.  Echoes from different objects,
or the same object at different orientations, produce
different echoes.  You can easily discriminate
"middle C" played on a saxophone versus a Fender
Stratocaster, and when you hear it you may be able to
recall what the instrument looks like.  But this does not
mean that the "middle C" note carried the visual
information.  The link between acoustic/echoic and visual
representation could also be learned through association.
 
However, all this does not preclude the ability of
echolocating animals to form representations of objects
that are object-centered, somehow independent of the
proximate echoic stimulus.  The ability to represent
objects independently of the simple acoustic features of
their echoes, and to integrate visual and echoic
information, makes sense.  Most objects produce different
echoes when their orientation changes, and a
multidimensional representation would be most resistant to
noise, changes in orientation, and so on.
 
The following all have excellent chapters on these topics:
 
Herman, LM (1980) Cetacean behavior:  Mechanisms and
functions.  Florida: Krieger.
 
Schusterman, RJ, Thomas, JA & Wood, FG (Eds.) (1986).
Dolphin cognition and behavior:  A comparative approach.
Hillsdale, NJ:  Erlbaum.
 
Nachtigall, PE & Moore, PWB (Eds) (1988).  Animal sonar:
Processes and performance.  New YOrk: Plenum.
 
Thomas, JA & Kastelein, RA (Eds) (1990).  Sensory abilities
of cetaceans:  Laboratory and field evidence.  New YOrk:
Plenum.
 
Thomas, JA, Kastelein, RA & Supin, A Ya. (Eds.) (1992).
Marine Mammal Sensory Systems.  New York:  Plenum.
 
Au, WWL (1993).  The sonar of dolphins.  New York:
Springer-Verlag.
 
cheers,
-------------------------
David A. Helweg
Department of Psychology, University of Auckland
Private Bag 92019, Auckland, New Zealand
FAX (+64 +9) 373-7450
email da.helweg@auckland.ac.nz