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

[Chris Campbell <sankarah@ou.edu>]

Jonathon Woolf wrote:
> 
> 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.  

And what's involved in an ambush?  A short chase, pounce, and
strangulation bite.  All felids are adapted for cursoriality.  All have
powerful jaws.  All kill by suffocation/strangulation.  Same with
canids, same with hyenas.

> 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.  

Uh, no.  Hyenas are about as far from ambush hunters as you can get. 
They chase, just like dogs.  None of this invalidates my point; the
particular methods differ dramatically, but the generalities
(cursoriality, strangulation/suffocation) are the same.  In particular,
the method of dispatch is very similar in all cases.

> 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.

Depends.  Horns work pretty well regardless.
 
> 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.

Right, true.  My point here is that Deinonychus would dispatch its prey
in a way compeletly different from any extant animals.  This means it
can take different prey, and perhaps larger prey, than we might expect
from a modern analog.
 
> > 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.

I hadn't heard that; I suspect both might be at work in both animals.
 
> > 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.

I'm wondering if it might not be high young adult mortality, though;
similar to wildebeest, though obviously for different reasons.
 
> > 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.

True.  And I expect it'd be no problem for a dozen Deinonychus to take
down a Tenontosaur.
 
Chris