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

["Larry Dunn" <larrydunn@hotmail.com>]

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?

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

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.

>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?  Were there no animals in the 
Cretaceous Period smaller than dromaeosaurs?  Or, even assuming pack 
hunting, 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. 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), catch a hold with those extremely avain 
forelimbs (somehow), kick once with the hindlegs, and then probably fall 
off.  And exactly what would just one such gash accomplish?  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.
 
>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.  We can't 
want killer raptors so badly that we lose sight of this.  

The cougar and deer you mention are being preyed upon, not losing 
numbers through attrition brought on by their own self-destructive MO.

>> 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.

Larry

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