Subject: Re: whale communication

Robert Kenney (rkenney@gsosun1.gso.uri.edu)
Thu, 13 Nov 97 10:30:51 EST

At 22:57 11/12/97 -0500, you wrote:
>Since whales can communicate over 1000 miles, what type of wave is used to
>communicate, what is the wave speed and wave frequency.
>
Do we know that whales communicate over 1000 miles?  First we need to agree
on what "communicate" means.  Here is what I would tell an animal behavior
class.  Communication requires several components:
(1) a signal sent intentionally by one individual (intentionally does not
mean that the animal thinks about it or plans it) that is received by another
(2) the signal changes the behavior of the receiver in some way, even if
it's only to affect the probability of the receiver's following behavior
(3) the change in the receiver's behavior benefits the sender

So what do we actually know about "long-range communication" in whales?  Not
much.  

-- The wave type is sound, so the speed is the speed of sound in salt water
(about 1500 meters per second or 3360 miles per hour, but it changes a bit
with changes in temperature, salinity, and depth).  

-- We know that low frequencies travel farther than high frequencies (the
laws of physics predict it, and the measurements to confirm are very easy to
do).  

-- We know that there is a depth in the ocean (about 1000 meters or 3000
feet below the surface) where sounds can travel the farthest (called the
deep sound channel).  

-- We know that some whales can make very low-frequency sounds, so low they
are below the range of human hearing.  Fin whales make sounds at about 20 Hz
(hertz or cycles per second); blue whales make sounds as low as 12 Hz.  

-- We guess that whales which make low-frequency sounds can also hear them.
It makes sense based on what we know about humans and other animals, but we
can't really do hearing tests on big whales (even if we could find
headphones big enough, they don't have thumbs to press the little button
when they hear the tone).

So what we actually KNOW is - IF a blue whales makes a 12 Hz sound while
diving down to 1000 meters, and IF another blue whale is also diving down to
1000 meters, the second blue whale could PROBABLY hear the first over 1000
miles away.  That still doesn't tell us if they are communicating, since we
don't know whether hearing the sound changes the behavior of whale number 2.
But that is a reasonable hypothesis (why else would whale #1 bother making
the sound in the first place)?

Cheers,
Dr. Bob  

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 | Robert D. Kenney, Ph.D.               rkenney@gsosun1.gso.uri.edu |
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