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Re: Long, long last gasp. (fwd)




David Marjanovic wrote:

> What about the following:
> Vision is more acute and less costly than echolocation. Therefore birds have
> an advantage (because all mammals have reduced eyesight), and use it to
> competitively exclude bats from getting diurnal. But when it's dark, vision
> is considerably less acute than echolocation, and bats will evolve good
> echolocation faster because mammal ears are better equipped for hearing
> extremely high frequences.
> 

This makes sense. Diurnal bats tend to hunt as much by smell as eyesight
(and by 'hunt', I mean find flowers and fruit). In fact tube-nosed bats
and the nasal structures on some sea birds (albatrosses, I think) are an
interesting case of convergence. I wonder if some pterosaurs may have
had such structures (if soft tissue, they may not fossilise). Most birds
however have a notoriously bad sense of smell (if any at all).

Of course, flying foxes also have incredible eyesight...

One interesting fact about microbat ears is that they are so sensitive,
they can be destroyed by their own out-going echolocation bursts. A
split second before vocalisation, one of the inner ear bones is pulled
back from the eardrum by a muscle, and returns a split second after the
out-going echolocating burst has be produced. So bats are actually deaf
for a moment during echolocation. It makes you wonder how they avoid
deafening each other in close confines.

-- 
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Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
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