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

[Chris Campbell <sankarah@ou.edu>]

Larry Dunn wrote:
> 
> From: Chris Campbell <sankarah@ou.edu>
> 
> >> 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;
> 
> (snip)
> 
> >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.
> 
> I'm talking behavior, not physics.  There isn't any terrestrial
> vertebrate that regularly preys upon another terrestrial vertebrate
> thirty times it's weight, even in a pack.  Why should it?  There's other
> prey to be had.  Why assume that extinct vertebrates did when extant
> vertebrates don't?

Okay, where are you getting these figures?  My copy of Dinosaurs: The
Encyclopedia gives weight differences of about 4-5 times; Deinonychus
comes to about 150-175 lbs and Tenontosaurus at about 4-5 times larger,
IOW about half a ton, max.  This is well within the range of
plausibility (particularly when you look at GSP's rendition of such an
attack on p, 337.  Since Ostrom originally speculated that D. probably
stuck to juveniles it's even more plausible.
 
> >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).
> 
> You've glossed over some very real differences here, even assuming that
> we look only at large mammalian predators as you've done.  Wild dogs
> chase down their prey in a pack, catch them from behind, stop them, and
> kill them.  Wolves encircle their prey in a pack.  Different strategies,
> both requiring speed and endurance, requiring  forelimbs for sustained
> running.  

Yes, different *chase* strategies.  Same method of killing, though,
which was my point.  D. used an entirely different method, which
drastically affects the type of prey it could be expected to bring down.

> Lions are built for a quick burst of speed and generally take
> on their prey individually, allowing AND requiring them to develop their
> forelimbs to assist in dispatching their prey.  And so on and so on.

Actually, this depends on the prey; buffalo and elephants are dealt with
communally, as are wildebeest on many occasions.  Nonetheless, the
method of dispatch remains the same: a strangulation bite, killing by
suffocation.

> Surely you're not saying that cheetahs and wolves are basically the same
> animals because they both suffocate their prey?

No, I'm not.  I'm saying that what they can go after is limited by the
fact that they have a given method of killing their prey.  They have to
be able to a) chase it down and b) apply that strangulation/suffocation
bite.  Deinonychus had a totally different method of killing its prey,
so the constraints we see in modern animals just don't apply.
 
> Mammalian predators are in fact quite diverse in anatomy and strategy.
> Nonetheless, what they all do as a rule is avoid tackling some behemoth
> that is likely to kill them.  Same goes when you open the floodgates and
> include the thousands of other terrestrial vertebrate predators.

Yes, true.  They are limited in what they can kill.  Consider what
happens when you add half-foot long canines to a lion: the options for
prey animals just increased a *lot*.  It's fairly easy to envision a
Smilodon killing an elephant or other large animal on a regular basis,
but aside from the Savuti prides we'd say that's a silly notion for
lions (heck, even the Savuti lions have a diet primarily of wildebeest
and Thompson's gazelles; they kill elephants and water buffalo on a
regular basis, but not as the staple of their diets).  Among modern
mammalian carnivores we have great variety within certain very limited
constraints (the suffocating bite).  When those constraints change we
can expect behavior to change as well.
 
> >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.
> 
> Why's their "potential prey" so big?  

Assumming we're talking about Tenontosaurus, here.

>Were there no animals in the Cretaceous Period smaller than dromaeosaurs?
>Or, even assuming pack hunting, just the appropriate few multiples bigger?

Given Ostrom's description of T., it seems to me that is *was* just the
appropriate few multiples bigger.
 
> >> 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.
> 
> There's no comparison between the forelimbs of a felid and the
> forelimbs of a dromaeosaur. 

I never said there was; I just noted that some extant predators don't
have any trouble holding onto a prey animal, even while it's moving and
bucking around.

>The only way that a dromaeosaur could have engaged in this killer claw 
>business would probably have been just as you say: to jump up (somehow), 

What, are you saying they couldn't jump?

>catch a hold with those extremely avain forelimbs (somehow), 

Forelimbs with sharp claws.  Again, see GSP's illustration in TDE.

>kick once with the hindlegs, and then probably fall off.  And exactly 
>what would just one such gash accomplish?  

A huge, gaping wound?  Those claws are designed to pierce, and deeply. 
An elephant wouldn't ignore them, much less the much smaller
Tenontosaur.

>Probably draw the attention of the tenontosaur so it could turn around 
>and squash the pipsquak who had such nerve as it fell off.  As you know, 
>herbivores don't take being preyed upon lightly.

Yeah, but unless they're Buffalo they usually can't do much about it. 
Also notice that predators are pretty good at taking punishment; we've
all seen the Discovery channel shows wherein a lion or cheetah attempts
to tackle a wildebeest alone, gets tossed all over creation, and finally
gets thrown off, tossed, trampled, or whatever only to get up bewildered
and wiser but otherwise unharmed.  So the Deinonychus leaps onto the
Tenontosaurus, gouges it with the big claw, hops off to scamper away
while the Tenontosaur turns to deal with its tormentor, only to set
itself up for a similar attack from the other side.  Heck, this wouldn't
even require any coordination; just pack members tackling whichever side
didn't have a bucking head attached.
 
> >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.
> 
> Life was probably very difficult for a hatchling Deinonychus, parental
> care or not.  It's a long and hard road to adulthood when you're a
> vertebrate. Once accomplished, you just don't throw it away.  

Tell that to wildebeest.  Five hundred thousand are born every year in
the Serengeti, and the population is quite stable.  That means five
hundred thousand, out of a population of a *million*, die off every year
during the annual migration.  There is, of course, one group of
vertebrates for whom life is cheap: those who are precocial.  I don't
know whether or not it's safe to speculate with Deinonychus; I don't
know how fast they grew, how long they lived, or any of the other
relevant data needed to determine such a thing.  I do know, though, that
if they are precocial predators life would be very cheap indeed.  And
let's face it, if they weren't terribly bright and didn't use
sophisticated methods to hunt, how much training do they need?

>We can't want killer raptors so badly that we lose sight of this.

Agreed.  And we can't want to tear down the image so badly that we lose
sight of other options.
 
> The cougar and deer you mention are being preyed upon, not losing
> numbers through attrition brought on by their own self-destructive MO.

But really, what's the difference?  The population's losing numbers;
that's all that counts for those breeding.  low numbers equals lots of
resources equals big clutch sizes.  The reason for the low numbers is
immaterial.  Further, large broods means kin selection can come into
play, making the maniacal attack strategy more plausible.

All of which assumes Tenontosaurus was a behemoth, and I'm not clear on
why you think that was the case.  I mean, it's not like it was a
Shantungosaurus or sauropod or anything.
 
> >> 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.
> 
> I wasn't limiting my comment to mammals.  Animals considerably stupider
> than dinosaurs (and that's saying something) are equally careful to eat
> things that probably won't render them two-dimensional.

To a point.  Remember Komodo dragons and water buffalo (which I keep
bringing up only because they're really nasty critters).  I'm not clear
on why said buffalo don't stomp the Komodo into oblivion after getting
bitten, but they don't.  The KD just sits back and lets the poor buffalo
die a lingering, bacteria filled death.
 
Chris