Re: Echolocation

From: Erich Hoyt (e.hoyt@virginnet.co.uk)
Date: Mon Jan 10 2000 - 17:58:16 EST


Echolocation is the detection of an object by means of reflected sound. The
animal emits a sound, usually at a very high frequency, which bounces off an
object and returns as an echo. Interpreting the echo and the time taken for
it to return allows the animal to determine the position, distance, and size
of the object, and so helps it to orientate, navigate, and find food.

Echolocation is known for certain in only a dozen or so toothed (or
odontocete) whale & dolphin species studied, mainly through studies in
captivity. But all the wild odontocetes studied also produce similar sounds
that could be used for echolocation.

Toothed whales produce the sounds used in echolocation in the complex soft
tissues of their nasal passages, inside the forehead between the skull and
the blowhole. A large, fatty, internal structure, the melon, seems to help
focus the sound forward and out into the water as a narrow beam. In the
sperm whale, the skull itself may act as an acoustic reflector to further
refint he sound beam.

Echolocation is important because the world that many cetaceans hunt and
navigate in has little and sometimes no light. Still, hunters, like orcas,
have good sharp color vision and no doubt use it whenever possible. One
strategy we used to notice transient, marine mammal-hunting orcas using in
the waters around Vancouver Island was to keep quiet! Perhaps they had found
that echolocation was enough to tip off seals and sea lions to their
presence. Fish-eating orcas definitely use echolocation, on the other hand.

Lots has been written about echolocation, and of course there is
echolocation in bats which was studied even before dolphins and whales. Even
so, we are far from a complete understanding. Most general books on whales
and dolphins have a reasonable summary and useful illustrations of
echolocation. For more depth, I recommend Roger Payne's book AMONG WHALES as
he was one of the pioneers in studying cetacean sounds; though his work has
focussed mainly on baleen whales, he also discusses dolphins and whales
based on the work of his colleagues.

With best wishes,

Erich Hoyt

----------
>From: CherryPie1016236@aol.com
>To: e.hoyt@virginnet.co.uk, pita@whale.wheelock.edu,
kburnett@whale.wheelock.edu
>Subject: Echolocation
>Date: Mon, Jan 10, 2000, 12:14 AM
>

> I am doing a project on echolocation and i was wondering if you could decribe
> that to me in detail. Thanks.



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