I need to know how various wildlife respond to different noise levels
in decibels.  What is the quietest sound they can hear, when do they
sense danger, when do they flee.  I realize different species are more
sensitive to different frequencies.  For this let's assume that the
noise source produces all frequencies at the same levels.  The kinds
of animals I need to cover are fish, deer/elk/moose, birds, bears,
butterflies, and maybe amphibians and reptiles--common animals that
you might see if you were, say, canoeing down a river in north
america.  It can be for a specific species like "King Salmon" or
general like "most fish."  Another way to answer this question would
be: how far away could these different animals hear a 100 decibel
noise source, how far away would they sense danger and how far away
would the noise be loud enough that they would flee?

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Request for Question Clarification by willie-ga on 06 Nov 2002 04:10 PST

There is a very good summary of research in this area at :
The Effect Of Noise On Wildlife: A Literature Review 
( http://interact.uoregon.edu/MediaLit/wfae/readings/radle.html )

Here's the abstract:
"Noise pollution, as it effects humans, has been a recognized problem
for decades, but the effect of noise on wildlife has only recently
been considered a potential threat to animal health and long-term
survival. Research into the effects of noise on wildlife, which has
been growing rapidly since the 1970s, often presents conflicting
results because of the variety of factors and variables that can
effect and/or interfere with the determination of the actual effects
that human-produced noise is having on any given creature. Both land
and marine wildlife have been studied, especially in regards to noise
in the National Parks System and the onslaught of human- made
cacophony in the oceans from military, commercial and scientific
endeavors."

Would this article constitute an answer to your question? Is so let me
know, and I'll post a summary as an answer.

willie-ga

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Request for Question Clarification by willie-ga on 06 Nov 2002 04:12 PST

Sorry - ignore that last question. I realised after re-reading your
question that you're looking more for info on the hearing range of
animals, rather than the effects of noise on them. The above article
is still a good read though.

Willie-ga

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Clarification of Question by tej-ga on 06 Nov 2002 14:15 PST

okay, let's just deal with a motor boat as a noise source.  is there
any info anywhere about how far away different animals might here it? 
would there be a point when the noise from a boat would cause animals
to sense danger and flee?  or is this something that varies widely and
depends on many other factors?

Generally animals with good hearing sensititiy can hear any sound as
loud as the background noise level, which can be quite low durring a
snow fall with no wind. Like humans, they tune out ordinary sounds,
such as distant thunder, but respond to sounds a preditor might make
even when it is several db below the noise level. As a result the
animal might not respond to a 90 db sound of one sort, but bolt in
terror at a 60 db sound. Minor differenses in pitch, harmonics,
modulation, rate, attack, intermodulaton distortion and other
qualities of sound may make 30 db (plus) differnce in the scare
factor. Like humans they learn to tune out, the sound of the
interstate, the roar of a water fall, and similar repetitive noises.
Experienced woodsmen can make an educated guess how each animal would
resond to the sound of an artificial duck call (or other) but
generally each sound would need to be tested for months to determine
if it repelled specific animals at a distance of one KM or one meter
where the same sound is a million times louder than at one meter. 
Neil

I got that backwards the last word should be KM not meter.

Also please take note that you would have to take into account how far
the sound would travel by itself.  This is in general affected by the
frequency of the sound, as well as the original amptitute (or
loudness) and the general surroundings i.e. any material that would
deflect, muffle the sound.

the research that you want is pretty hard to determine without some
cruel manipulation on the animals themselves, as unlike human hearing
testing where you could get the human to signal to you whether they
could hear a sound or not, we would need to wire up the animals and
try to detect if the neurons within the ears were firing signals
corresponding to different degrees of loudness to different
frequencies - not a very kind test that anyone would want to inflict
on any creature.