Re: The absurdity, the absurdity (was: Cooperating theropods?)

[Jonathon Woolf <jwoolf@erinet.com>]

Chris Campbell wrote:

> > >But you have to look at more than weight differentials.  You also have
> > >to look at likely hunting techniques, life history strategies, build,
> > >and so on.  All of these things are very different from those of living
> > >species, so we can't directly compare the two.
> >
> > As a rule of thumb, pack-hunting mammals do not prey upon animals that
> > exceed their own weight by more than a few multiples.  This is true of
> > both wild dogs and lions, although the hunting strategies, body
> > configurations, etc., of each are very different.  Assuming that
> > dromaeosaurs were as active as mammals (a *very* generous assumption
> > indeed), they would follow the same rules.
>
> Why?  You say the hunting strategies and body configurations of dogs and
> felines are very different, but I would very much disagree.  All are
> adapted for cursoriality, all have powerful jaws, and all kill by
> suffocation.  All of them.

Um, well, no.  As Larry also observes, canids tend to be chase hunters, while
felids are almost exclusively ambush hunters.  African wild dogs (hunting dogs,
painted wolves, _Lycaon pictus_ for the taxonomically inclined) are fearsomely
effective predators, precisely because they are the only chase hunters in a 
world
otherwise filled by ambush hunters -- the big cats and the hyenas.  The tactics
that work against a cat that can only run a hundred meters before dropping don't
work against a predator that can dog the prey's heels for miles, until the prey
animal finally tires and falls.

And both wild dogs and wolves have another unusual habit: when faced with large
animals that take a lot of killing, they have a disturbing tendency to settle 
for
crippling the prey by hamstringing it or something similar, then just dig in
without waiting for it to die.

> Looking at our dromaeosaurs, it's pretty clear the same options wouldn't
> be available to them.  They're bipedal and their potential prey is too
> large for the suffocation strategy.  This means a totally different
> strategy would have to be employed.  Once we start down that road, all
> of our assumptions get pitched.

True enough, assumptions often just hinder hypothesizing.

> Those external pressures are exactly what's important here, though.
> Consider what happens when dear or cougar hunting is allowed to
> increase; the rates of reproduction in the population as a whole
> increase dramatically.

Cougar hunting I don't know, but in deer hunting, it isn't always the rate of
reproduction that increases.  More often, it's the rate of reproductive 
_success_
that increases, because there aren't so many adults eating all the food and
there's more left for the kiddies to eat.

> Is it so unreasonable to imagine that this might
> be taken to an extreme in a species, to the point where large clutches
> are laid because of high young adult/adult mortality?

Well, there certainly had to be _some_ reason for the high clutch size in
dinosaurs.  I think high juvenile mortality is as good a reason as any.

> Still, even if you only include zebra and wildebeest (regular meals) the
> weight difference is enormous.  These dogs aren't very big; weight is
> 17-36 kg (Walker's again), compared to 118-275 kg for a wildebeest and
> 175-385 kg for a zebra.  That's a weight difference of about 10 times,
> at least for the zebra.  Pretty impressive.

OTOH, wild dogs generally hunt in packs of ten to twenty.  I tend to think that
the mass difference that's important is the total, not individual predator to
individual prey.  It's a lot more impressive for one wolf to take down a moose
than it is for ten wolves to take down a moose.

-- JSW