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Re: Dromeosaurid behavior........Pack hunting! (long)



Well,
      If you look at all the response that we have been getting about this
subject (most of the messages are for pack hunting in only
D.antirrhopus.),  people seem to agree with me to a certain point.  That
point being, only D.antirrhopus hunted and lived in well organized packs.
I'm stating that as well, I certainly don't believe that all dromeosaurids
hunted in packs.  The evidence for the idea of pack hunting in
D.antirrhopus maybe hard to except for many but it isn't hard to look at
and say "Hmmm, I think D.antirrhopus hunted in packs, or maybe not.".
That's what I'm saying.  D.antirrhopus may have been the only dromeosaurid
to hunt in packs.  Plus you have to remember, dinosaurs lived on this
planet over 200 million years.  They evolved into fantastic creatures.
Some of them actually developed social behavior, such as the Maiasaurus
and several of the sauropods (I maybe wrong on that though.).  Why
couldn't some of the carnivores develop such behavior, it would seem
logical.

--MegaRaptor

Matthew Bonnan wrote:

> MegaRaptor:
>
> It sounds like you really like dromaeosaurids, especially Deinonychus
> (who wouldn't?), and I think you've convinced yourself that pack
> behavior in these animals is inevitable.  I am a graduate student now
> working on my Ph.D.  You've probably been interested in dinosaurs for
> a while (I'm guessing) and I know when I was 17 (I'm 26 now) it seemed
> that a lot of the scientific community were way to conservative and
> hardnosed when it came to interpreting dinosaur behavior.
>
> First of all, it's good to see you've put some thought into this, but
> it's hard to really know what is going on with specimens unless you
> actually see them in three dimensions, or visit certain dinosaur
> localities, etc.  I'm not suggesting you haven't done this, but my
> guess would be that most of your exposure to dinosaur data has been in
> museum displays and perhaps you've participated as a volunteer on
> dig?
>
> Let me tell you, from my own experience with sauropod dinosaurs, that
> you can look at hundreds of photographs and illustrations and still
> not really understand what is going on with a fossil animal until you
> actually hold the thing in your own hands, turn it around, look at it
> from various angles, measure it, etc.
>
> And of course, these animals, no matter how alive they are in your
> head, are very much dead.  We only have a very narrow amount of
> information available to us, because these animals first had to die,
> their carcasses had to "survive" scavenging, their remains had to be
> buried fast (and only in certain sediments at that), the remains have
> to fossilized, the remains can become distorted, then they erode out,
> someone has to catch them at the right moment, not all the bones are
> collected, their remains are brought to a collection, they're
> prepared, and then finally a paleontologist can begin to really look
> at the bones and describe them!
>
> So, with that in mind, there are more things to consider.  We cannot
> (although wouldn't it be awesome if we could?) observe living
> dinosaurs doing their things.  We have to collect extremely indirect
> evidence, and in most cases it is equivocal -- not supporting or
> rejecting our hypotheses.  But let's examine your hypothesis ...
>
> When we come up with a hypothesis in science, we try to phrase so
> that we are likely to REJECT it.  Once you have an idea you really
> like (I know I have a few about dinosaurs myself), it is very easy to
> find evidence to confirm, at least to yourself, that you're right.
> But we want to try to get rid of our own personal biases as much as we
> can.  Otherwise, we might overlook or subconsciously ignore
> contradictory or vague evidence.
>
> So, we could start out setting up a hypothesis like this:
> Dromaeosaurids did not hunt in packs to bring down big prey like
> Tenontosaurus.  We would call this your null hypothesis.  Then we set
> up a different, or alternative, hypothesis like this: Dromaeosaurids
> did hunt in packs to bring down big prey like Tenontosaurus.  In every
> case where the evidence is equivocal or vague, we fall back on the
> NULL hypothesis.
>
> Let's look then at the Tenontosaurus situation.
>
> Evidence 1: Deinonychus and Tenontosaurus are both known from the
> Cloverly Formation.  Of course, just because two animals are found in
> the same locality doesn't mean that they interacted with each
> significantly.  We fail to reject our null hypothesis here.
>
> Evidence 2: There are teeth of Deinonychus present with Tenontosaurus
> remains at more than 16 sites in the Cloverly.  Okay, we have teeth
> associated with this big herbivore.  But here are some things to
> consider.  The teeth may have been shed during an attack, but there is
> no evidence at any of these sites to outright reject the possibility
> that these Dromaeosaurids were just being opportunistic scavengers.
> The teeth could just as easily be shed by scavenging theropods as well
> as actively predating ones. Hmmm ... looks like we can't be sure
> again, so we fall back on our null hypothesis again.
>
> Evidence 3: Some specimens of Tenontosaurus appear to have bite marks
> in the bones and are also associated with Deinonychus teeth.  Great!
> Irrefutable evidence, right!  But, wait!  Who made the bites?  How do
> we know that another dinosaur, or even something like an alligator,
> didn't make the bites?  We don't.  It's really tough to match up teeth
> marks with dinosaur jaws, because teeth can slip, or not penetrate in
> certain areas, or any other number of problems.  And even if we were
> to show that indeed Deinonychus or another dromaeosaurid bit the
> Tenontosaurus, it wouldn't tell us whether the bite was made during an
> attack or as a scavenging mark.  Too bad, but it looks like we have to
> fall back on our null hypothesis again.
>
> Evidence 4: Tenontosaurus is too big for one dromaeosaurid to handle.
>  Pack hunting was obviously necessary to bring them down.  Well, okay,
> but this assumes that Deinonychus had pack instincts, something we
> can't directly observe.  Plus, maybe once a Tenontosaurus got big
> enough, it was left alone.  Maybe if Deinonychus was a pack hunter, it
> attack juvenile Tenontosaurs.  And, it turns out, a subadult
> Tenontosaurus MOR 682 at the Museum of the Rockies was found in close
> association with 11 shed Deinonychus teeth.  The skeleton appears to
> have ripped apart pretty good by some dinosaurs and perhaps this
> indicates that many Deinoychus were employing pack tactics to bring
> this smaller guy down.  Or, this smaller guy was killed by a bigger
> theropod and then scavenged by Deinonychus.  Or, this smaller guy died
> of other causes and was later consumed by Deinonychus.  And even if
> these animals didn't have pack behavior, they could be drawn to a
> stinking carcass like vultures.  So again, our evidence is equivocal.
> We fall back on our null hypothesis yet again.
>
> Well, we could go on like this for a long time, but I hope you see
> the point I'm trying to make.  As scientists, we are duty-bound to be
> skeptical of every new (or even not so new) claim until we find
> evidence that positively supports that claim, or hypothesis.  And
> remember, every hypothesis and theory in science, in order to be
> scientific, has have these four qualities: 1) It has to be testable;
> 2) It must be repeatable by other researchers; 3) It must be
> falsifiable; and 4) It should have predictive power.
>
> Science is a tough business, and paleontology is extra hard because
> we don't have as much control over the evidence as do some
> experimental scientists.  Even though it would be awesome if theropods
> hunted in organized packs, dispatching hadrosaurs and sauropods left
> and right with cool, calculated efficiency, we just don't have enough
> positive evidence to say, definitely, yes this is what happened.
>
> But this is where you come into the picture.  How badly do you really
> want to know and see and touch the real evidence?  Maybe there's
> something the scientific community is missing, or hasn't considered,
> or hasn't looked at, or who knows?  New technology may come along to
> help us address questions we can't even fathom answering or even
> asking now.  If you want to become a paleontologist, maybe you can put
> your mind toward figuring out just what the behavior of dromaeosaurid
> theropods was like.  It will take a lot of math, anatomy, physiology,
> ecology, behavioral studies, geology, and even more determination and
> perserverance.  And maybe after all that you will still not know the
> whole story.  That's the risk but that's also your chance to possibly
> change the way we currently look at theropod behavior.
>
> Finally, I should add that some of the information above I got from
> the following sources.  It's important, where ever possible, to give
> credit to previous researchers, even if you don't agree with their
> conclusions.  Good luck with your question, and feel free to ask more.
>  On this list, we can't always return responses right away (most of us
> our very busy with our research, teaching, and other stuff) but don't
> be discouraged.  At the very least, use the library frequently and
> always look for evidence that does not confirm your ideas.
>
> Forster, C. 1984. The paleoecology of the ornithopod dinosaur
> Tenontosaurus tilletti from the Cloverly Formation, Big Horn Basin of
> Wyoming and Montana.  The Mosasaur, 2: 151-163.
>
> Glut, D. 1997. Dinosaurs: The Encyclopedia. North Carolina: McFarland
> & Company, Inc., Publishers.
>
> Maxwell, W. D., and J. H. Ostrom. 1995. Taphonomy and paleobiological
> implications of Tenontosaurs-Deinonychus associations. Journal of
> Vertebrate Paleontology, 15(4): 707-712.