RE: COMPETING BATS, BIRDS & PTEROSAURS

[Ronald Orenstein <ornstn@home.com>]

At 11:30 AM 28/02/01 +0100, Jarno Peschier wrote:
> Maybe in reality that's the other way around? Birds already existed (let's
> assume that bats evolved later than birds even thought that's probably far
> from 100% certain) and already had good eyesight so they primarily dominated
> the day time. Bats had to try and do their stuff at night to avoid direct
> competition with the ever present bird during the day. This in turn was a
> strong selective pressure that caused the bats to quickly "develop"
> echolocation.

Let's not forget that not all bats echolocate, and some birds do.  The 
echolocating birds (swiftlets and the oilbird Steatornis caripensis) breed 
in caves, as do many (but not all) echolocating bats, and apparently do not 
use echolocation to find food (swiftlets are diurnal and the oilbird is a 
fruit-eater).  Though not all echolocating bats are cave roosters, it is at 
least possible that echolocation evolved in both groups as an adaptation to 
living in caves and only later, in the Microchiropteran bats, became useful 
for food-finding (and reached the level of sophistication seen in bats; 
echolocating birds use a lower (audible) frequency which I gather is less 
precise at object discrimination and does not have the added property of 
being able to "jam" insect hearing systems).  This idea would allow for the 
early stages of echolocation in bats to have a functional role in a less 
precise form; I believe that the only megabat to echolocate is also a 
cave-dweller that does not hunt by echolocation, though as I am not at home 
I cannot check on this.


--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@home.com