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Re: Gr. 9 Sc: Pesky Harmonics



bruce thompson wrote:

<snip>

> 
>         Why might the predators be unable to hear the low frequency
> vocalizations?
> 

The problem isn't predators detecting high-frequency sounds so much as
it is predators being able to localize high-frequency sounds.  HF sounds
are easy to "lock onto" and determine the direction and approximate
distance. LF and ELF sounds are much harder to lock onto, simply due to
the mechanics of how sound travels.  Therefore, the idea goes,
low-frequency sound is "safe" to use for communication while
high-frequency sound isn't because high-frequency sound tells predators
where you are.

A book I read recently seems to imply that this entire idea is based on
a huge fallacy, but the reasoning is somewhat fuzzy and very tentative. 
The book is WHY BIG FIERCE ANIMALS ARE RARE by ecologist Paul
Colinvaux.  In it, he shows that in modern terrestrial ecosystems, large
mammalian predators are not a significant check on the numbers of large
mammalian herbivores.  A strong implication of this is that healthy prey
animals have little reason to fear being detected by a predator.  If
this can be extrapolated to dinosaur predator-prey relationships, then
attempts to explain away high-frequency sound from hadrosaurs may become
unnecessary.  

-- JSW