Re: Long, long last gasp. (fwd)

["David Marjanovic" <david.marjanovic@gmx.at>]

I wrote...

----- Original Message -----
From: "David Marjanovic" <david.marjanovic@gmx.at>
Sent: Thursday, January 29, 2004 10:40 PM

> > perhaps suggesting that predator avoidance isn't the main reason
> > why bats are largely nocturnal. I suspect niche partitioning; perhaps
> > birds are better at catching the same types of prey as bats do, so bats
> > avoid direct competition by hunting at night.
>
> 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.

While echolocation does seem to be costly, it may not be less accurate than
vision. http://www.nature.com/nsu/010208/010208-1.html (requires a free
subscription) describes that bats plunge into bushes to pluck out beetles,
and are capable of chasing each other without getting utterly confused by
all the echo.

I should also have been clearer about bird and mammal ears: both types can't
evolve to hear frequencies above a certain threshold (without evolving into
another type...), and that design constraint is lower for birds than for
mammals. Of course, most mammals (at least) can only hear frequencies far
below both thresholds.

Special thanks to HP Mickey Rowe :-)