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Re: Phorusrhacids killing large mammals in National Geographic Channel

On Mon, Aug 10, 2009 at 12:25:15PM -0500, Raptorial Talon scripsit:
> > In the case of anything fossilized, it is very, very, very hard to avoid 
> > theorizing in advance of the data, which is something we shouldn't do.
> Not in published papers, anyway. :P

It's generally a bad habit to get more than one step of implication away
from a nice, solid fact, even so.

> > I'd also like to note that extant or recent high-predator-diversity
> > ecosystems have two things in common; multiple sizes of diverse large
> > herbivores, and at least some of the herbivores are migratory
> > herbivores.  This tends to suggest that unless both those conditions are
> > absent, we shouldn't be looking for predator/predator competition as an
> > extinction mechanism.
> I did not know that about predator diversity. Very interesting . . .
> 'course, I for one can't be sure how that would intersect with mass
> interchanges and the resultant ecological restructuring.

Well, no one can, that's part of the problem.

> Are *any* large mammals in South America migratory to any degree? I
> certainly can't think of any that are. And now I'm wondering about the
> Indian region, too . . . I don't know what's migratory there, or if it
> can properly be considered a high-diversity locale for predators
> (tigers, leopards, wolves, dholes, bears, hyenas - seems that way, I
> guess). I'd sure like to find out, though.

Historically, yes, there was at least a lowlands/uplands seasonal
migration going on.  Pre-human-settlement patterns are going to be
mightily difficult to reconstruct.

The North Amercian list is longer than either the India or Africa list
-- short faced bears, grizzly bears, polar bears, black bears; three
species of wolves ("buffalo" wolves, timber wolves, coyotes); lions,
cheetah, puma, jaguar; this may -- though I do not know how to go about
proving this -- be correlated with scale and scope of migrations, which
are substantially unimpeded north/south in NorAm.

Of course, this also raises the question of how you got T. rex and only
T. rex in what looks like a herbivore-diverse migratory environment.

-- Graydon