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

[Chris Campbell <sankarah@ou.edu>]

Larry Dunn wrote:
> 
> From: Chris Campbell <sankarah@ou.edu>
> 
> >The problem with that idea is that there *are* no modern analogs.
> >These animals are so different in form that you can't really compare 
> >them to extant animals.
> 
> I'm not sure I accept the rationale that, because theropod dinosaurs
> weren't "configured" like extant vertebrates, that all bets are off and
> it's time to begin the wild speculation.  There are certain "rules"
> observed in extant vertebrates regardless of their configuration; if we
> are going to speculate about these animals (and, of course, we are),
> it's more realistic to use these rules than our imaginations.

And what are those rules?  One might say a 7 ton animal has to have a
graviportal skeleton, but one look at T. res would dispel that notion
real quick.  The rules are easily broken, even by extant animals.
 
> >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.  The only real difference is the method of
delivering that killing blow; lions jump on their victims and maneuver
for a bite to the throat, cheetahs trip their prey up, dogs wear their
prey down so they can clamp down on the muzzle, and so on.  The goal is
the same: kill the victim via suffocation (assumming, of course, that
we're talking about reasonable large victims; mice and rabbits would
naturally be dispatched by more conventional means).  

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.
 
> >I just can't see a reason to think it's that remote, though.  Those
> >claws couldn't have been used for anything other than slicing (they're
> >too well designed for that role), and the dromies couldn't use them on
> >anything other than big animals.
> 
> The dromaeosaur giant-killer scenario has repeatedly been called into
> question.  The utility of the claws for cutting is a matter of
> contention, and some have argued that the "hands" and forelimbs of
> dromeaosaurs with their limited range of movement were simply not suited
> to hanging onto a wildly bucking multiton herbivore.  In any event, even
> assuming away all of these problems, the physical challenge of holding
> onto a moving prey animal with forelimbs and kicking claw-equipped
> hindlimbs through the prey animal's hide seems almost insurmountable.

Okay, why?  Since I've just argued against such things I can't bring
modern animals in for comparison, but I notice that cats don't seem to
have any trouble holding on to their prey; why would dromaeosaurs? 
Couldn't they just jump, latch on with their forelimbs for a moment of
stability, kick, and fall off?  I'm not imagining them leaping and
sticking so much repeating a simple strategy over and over again until
the prey animal stops moving.
 
> >  You've said it's ridiculous to think that they'd lose three of their 
> >number in an attack, citing modern mammals as evidence, but the comparison
> >isn't valid.  Dromies layed eggs and lots of 'em; this might let large 
> >numbers of them survive to maturity, which would mean they'd be less 
> >likely to worry about individual survival. None of this proves a damn 
> >thing, of course, but it does make the hunting idea plausible.
> 
> First, how do we know that dromaeosaurs had large clutches of eggs?  

Granted, this is an assumption on my part.  We don't have much in the
way of fossilized eggs for dinosaurs in general, let alone for
dromaeosaurs, so it could be way off.

> In any event, animals which lay large numbers of eggs do not do so
> because their young all mature, then die while hunting huge herbivores;
> they lay large clutches because infant mortality is very high.  It's
> simply impossible for vertebrates to invest the resources to have huge
> broods and then assure that they all survive.  (I'm not going to get
> into the external pressures that lead to these various repro strategies;
> it's been discussed here in past years.) It's one or the other; either
> have a few young and nurture them carefully or have a lot so that a few
> survive.

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.  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?  Like I said
before, this isn't evidence for anything; it just makes such a strategy
somewhat plausible.
 
> >True.  Also, it's not unreasonable to assume that Deinonychus hunted
> >Tenontosaurs with good success, and that the site under discussion was
> >just a freak occurrence.  Heck, they might have killed it without
> >losing a member and then got swept up in a flash flood or something.
> 
> I've never really bought the idea that, because animals' remains are
> found together at a fossil site, that they were all hanging out together
> when they died.

That's a perfectly valid point, one I tend to agree with.  Given the
frequent association of Deinonychus teeth with Tenontosaurus remains,
however, I think it's more plausible here than it is in most cases.
 
> But anyway, for reasons I've discussed before both in this and previous
> posts, I see no reason at all to assume that Deinonychus preyed upon
> Tenontosaurus, and very good reasons to assume they did not.

I haven't seen too much reason to go either way, myself.  It still seems
like a very open question to me.
 
> >A fair point, but we also have to remember such things as hunting dogs
> >killing water buffalo, wolves killing bison and moose, lions killing
> >elephants, and so on.  These are not unusual occurrences, so we have to
> >keep an open mind about what the possibilities are, especially in light
> >of differences in build, probable life history strategies, and
> armament.
> 
> I don't think that wild dogs (is that what you meant by "hunting dogs"?)

Yeah, African hunting dogs.  It's a real name; check Walker's.

> generally kill water buffalo (sure, maybe there's some mutant pack
> that's doing it, but generally Water Buffalo are too big for lions to go
> after, let alone wild dogs).  

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.

And as already noted, Savuti lions go after buffalo on a regular basis,
despite the avalibility of other prey animals.

>And I think we have in fact agreed that the elephant-eating lion prides 
>are *very* unusual.  

They are, but only for lions.  Remember the elephant eating tigers from
India and Nepal?  They take immature elephants all by their lonesome. 
Of course, said tigers are really fraggin' big, but still . . .

> The exception rather than the norm.  Probably better to use the norm 
> to hypothesize about the behavior of extinct animals.

And agree that exceptionally nutso deinonychus packs might have taken
hadrosaurs?  Sure, I can agree with that.  :)
 
> >But think about it: given that sickle claw, pack hunting would 
> >require no coordination at all.  All you'd need is a "scream and 
> >leap" mentality and a will for mayhem, and you could take down whatever 
> >you felt like.  Larger numbers just mean larger animals.
> 
> This is the heart of the entire problem.  We need to avoid the
> anthropomorphizing of theropods.  What current predatory animal has "a
> scream and leap mentality"?  What current predator engages in "mayhem?"

What current predator is armed with giant claws designed to flex through
180 degrees of motion?  None that I know of.  But, to answer your
question: lions.  Again, the Savuti prides, but you asked . . .

> Why, none, I would say.  Predators just do not blindly hurl themselves
> at huge herbivores for the fun of drawing blood, then enjoy the carcass
> if they've survived and it's Miller Time; they carefully select prey
> based on likelihood of success and minimalization of risk.

Yes, now.  We have to be careful not to assume dinosaur predators acted
as mammalian predators do; mammals have a fair amount of grey matter
between their ears, and this lets them be more careful about selecting
prey.  I'm not sure you can make the same assumption about dromaeosaurs.
 
> In my humble opinion, the animals are actually more interesting when we
> see them with their likely natural talents and limitations rather than
> simply as scaly hitmen.

I agree; the only reason I wrote the above was because I wanted to get
some Niven in here, okay?  I don't normally think about animals like
that.
 
> >But can we keep intrepid beetles?  :)
> 
> But of course.  What would life be without I.B.'s?

Oh, very dull indeed.  :)

Chris