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Re: Phorusrhacids killing large mammals in National Geographic Channel

On Sun, Aug 02, 2009 at 01:48:35PM -0300, Augusto Haro scripsit:
> Graydon wrote:
> > Extant wolf populations are remnants everywhere.  This is not true of
> > the African wild dogs or hyaenas.
> With remnants you mean, small populations vulnerable to extinction?

The survivors of human extermination efforts either of them or their
primary prey species.  They've all been heavily selected for caution
*and* (at least in the southern edge of boreal Canada) reduced size.

> In such a case, this is also true of African wild dogs. 

But the wild dogs still have to compete in terms of _eating speed_ with
the arrival time of the local pride of lions.  This may never have been
true of wolves; we don't know how they handled niche partitioning when
there were sabertooth cats and North American lions and short-faced
bears around to compete with, other than that they were substantially
larger than the extant ones.

> Also, I am not so sure the danger a species or population have has to
> do with the care the individuals of a pack put in preserving their own
> lives... (I suppose they have little worry of the future of their
> species).  Although I think an individual has better chances of bring
> descendants when other individuals (overall of the other sex) around,
> group selection is somewhat complicated to prove...

I don't mean group selection; I mean that wolves -- specifically wolves
-- have been selected for caution by interactions with humans, and how
wolves *used* to act with respect to megafaunal prey 50 or 250 kyears
ago is not well known.

So trying to extrapolate from the behaviour of extant wolves is very
risky, especially in context of giant ground-running predatory birds, of
which we have no examples.

-- Graydon