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Re: Mammals preying on giant azhdarchid pterosaurs!




On Sun, 21 May 2000, Larry Dunn wrote:

> --- John Bois <jbois@umd5.umd.edu> wrote:
> 
> > Pollyanna might agree.  But the fossil record is
> > filled with creatures
> > which could not evolve strategies to counter certain
> > predator
> > strategies.  They are extinct.
> 
> Interesting, and I'd definitely like to know more. 
> Please give me an example of a species that was
> terminated by inabilitiy to cope with predator
> strategies.  In line with the discussion, please
> exclude extinctions caused by humans or human
> introduction of predators.  Most importantly, please
> cite the evidence that proves that the extinction was
> caused by predation.  Thanks.

I was responding to the claim that prey, unless they are on islands and
are being invaded by novel creatures, always evolve defenses to escape
predators and thus avoid extinction.  Of course, extinction has many
causes.  Among proximate agents, competition and predation are widely
regarded as important.  But, the specific cause, chain of events of an
ancient extinction event cannot be known.  Still, given the modern record
of geese, ducks, ground nesting birds on Barro Colorado Island, the
hypothesis that predation comes into play at least in synergy with habitat
loss must be seriously considered.  My previous answer was not intended to
be categorical (because I really do have a grasp of the complexity of real
extinctions and an awareness of the lack of evidence of specific
events).  It was meant to rhetorically counter what I regard as a
totally unrealistic claim, an hypothesis unworthy of consideration, viz.,
animals always evolve themselves out of trouble.  My _opinion_ is that at
least some animals became extinct because they could not cope with
novel predator tactics.  So, yes, I should have put a "probably" or a
"might have", or whatever in the sentence.