Re: All this flying talk---then comes the why..or something

[Ronald Orenstein <ornstn@inforamp.net>]

>BCF asserts that the arboreal lifestyle, though not specifically flight, in
>archosaurs was likely but not certainly a response to predation: small
>archosaurs found refuge from larger predators in the trees and perhaps in
>other high places, such as cliffs.

It's hard enough to determine whether a small gracile fossil dinosaur could
have been arboreal - surely it is impossible to tell why!  I fail to see why
this explanation is any more likely than suggesting that becoming arboreal
exposes an animal to a whole new range of food sources (insects, frogs,
lizards
etc). I suspect that this is why so many living birds are arboreal, if only
because I do not see any evidence that terrestriality exposes them to higher
predation (except for the vulnerability of island ground-nesters to introduced
predators).  This is partly because, today, there are a lot of arborial
predators that weren't around in the Jurassic, of course (hawks, martens etc),
but I still think niche exploitation is as likely, or more likely, an
explanation for any arboreality dinosaurs may have shown (and of course there
is no unequivocal proof that they showed any!) than predator avoidance.  In
fact I can think of no case in which any living species moved into a new niche
(as opposed to developing defences) purely to avoid predators.
--
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@inforamp.net