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



At 10:00 AM 5/1/99 -0500, MegaRaptor wrote:

>> >The discovery of the Tenontosaur skeleton and the several D.antirrhopus
>> >skeletons only proves that at least on species of dromeosaurids hunted
>> >in packs.
>>
>> Unfortunately, it doesn't prove it.  It *could* be consistant with a Komodo
>> dragon-model: one or two individuals bring down a prey item, then others
>> (who were not involved with the kill nor are associated with killers by
>> bloodline) come by to scavenge at the carcass.
>>
>
>I wouldn't think it would be consistent with the Komodo Dragon-model. 
>These
>animals were built to kill in small, well organized packs.

Indeed?  Why, then, is there no evidence for pack hunting in _Velociraptor_
or other dromaeosaurids, dinosaurs of very similar anatomy?  Are felids
"built to kill in small, well organized packs?"  Some felids do, some felids
don't, but most have very similar anatomies.  Are canids "built to kill in
small, well organized packs?"  Some canids do, some canids don't, but most
have very similar anatomies.  Are hyaenids "built to..."... Well, you get
the picture.

Morphology can inform us to some degree about behaviors (for example, it can
suggest or eliminate certain types of predatory strikes or food
manipulation).  However, no one has yet demonstrated a physical anatomical
condition which correlates with organized pack hunting.  Wish there were
one, but nobody's found it yet.

The Komodo dragon model isn't very romantic, but it would still be
consistent with at least some of the evidence.  The data that led Ostrom to
suspect _Deinonychus_ as a pack hunter was *NOT* it's elegant anatomy: it
was the association of certain bones and teeth in the rock record, from
multiple sites.

> These were
>supposed
>to be some of the most intelligent dinosaur at that time.  With
>intelligence
>comes organization, am I right?

Not necessarily.  It certainly helps, but are lions more intelligent than
tigers?  Than leopards?  One species is a fanatastic pack hunter; the others
hunt alone or in very small groups.  Is there any sign of difference
intelligence between them.

In Science, "could be" is *NOT ENOUGH*.  Science is driven by data, by
evidence.  Speculation unconstrained by physical evidence is part of what
gives dinosaur paleontology a bad name in many scientific circles (including
within the field of paleontology itself).

(Okay, this may surprise some of you out there, but being a dinosaur
paleontologist is not the most respected of fields within the
paleontological community).

>>
>> Also, I think that the site (where the babies were feeding on bones on large
>> individuals) to which you refer is *NOT* a dromaeosaur site: it is Bakker's
>> allosaur ("Wyomingraptor") site.  Different dinosaur entirely.
>
>I don't think it was the Allosaur  "Wyoningraptor", I saw an episode of
>Paleoworld that dealt with dromeosaurids and their life style.  Bakker
>actually
>showed a Tenontosaur bone with wounds from large and small dromeosaurid
>teeth.

Ummm...  If you note, I was IN that episode (championing pack hunting for
dromaeosaurids, by the way).  I  have it on tape.  The specimens Bakker show
are from his Wyomingraptor quarry.  He calls them "raptors", but they are
allosaurs.  I REALLY wanted the editors to not use that sequence, but such
is Life...

>> Yes, there are advantages to pack hunting.  However, there are
disadvantages to
>> being a solitary hunter, too.  Or an "opportunistic gang hunter" (not an
>> organized pack of close kin, but random members of a population who converge
>> on a kill site: sharks, for instance).
>
>It doesn't make sense to me that being opportunistic while hunting is a
>advantage, it's more like a disadvantage.

Nevertheless, it works.  Sometimes different strategies work in different
ways, but achieve the same end (survival of that particular lineage).  If
pack hunting were the best way of hunting, why aren't all felids and canids
and hyaenids (and monitor lizards and rattlesnakes and hawks and frogs...)
pack hunters?  Different strokes for different taxa.

>During the times of the year
>that
>most of the herds moved south for the dry season the dromeosaurids would
>have
>likely followed them.

There is no evidence I have heard for migrations in the Cloverly.  Not
impossible, of course, but no evidence for them yet.

>> In Nature it is very rare for a single strategy to be "The Best".  That is
>> one of the reasons for the vast diversity of life now and in the past.
>
>I don't know what you meant by "a single strategy being 'the best'"

I meant that Nature doesn't guarentee that a particular adaptation (say,
pack hunting) is better than all other forms of hunting. It might work well
for one lineage in one environment, but not for others.

>> Incidentally, I think that Ostrom & Maxwell's work does show that
>> _Deinonychus_ was a pack hunter.
>
>Thank you, it was most likely only D.antirrhopus that was a pack hunter,
>but we
>cannot rule out the rest of the dromeosaurids.

Of course we cannot rule them out.  However, we don't have *evidence* for
it, and as I've been trying to emphasize all along, it is evidence you need
to demonstrate complex behaviors.

>> However, demonstration of pack hunting in one species of dromaeosaur by no
>> means shows that *all* dromaeosaurids were pack hunters: after all,
>> _Panthera leo_ is a pack hunter par excellence, but its very close relative
>> _Panthera tigris_ is a solitary or pair hunter for the most part.
>
>True, maybe one or two species were solitary hunters and not pack
>hunters like
>D.antirrhopus.

Or maybe all?  Or maybe none?  Without evidence to guide us, we cannot say.
If you are going to go into paleontology, you will have to accept the
sad-but-true fact that sometimes "We can't tell" is the only valid answer.

>>
>> Pack hunting is a specialized behavior, and it is contingent on the person
>> proposing pack hunting for a particular fossil species to show some sort of
>> evidence (taphonomic, for instance) supporting that hypothesis.  Otherwise,
>> the more common behaviors of solitary or "gang" hunting should be considered
>> more likely.
>
>"Gang hunting" isn't really hunting, it's more like an ambush. No
>offense though
>Mr. Holtz.

A) Ambush predation is an entirely different subject.  Lions are ambush pack
hunters; leopards are ambush solitary hunters; wolves are pursuit pack hunters.

B) Carnivore ecologists would strongly disagree with you that "gang hunting"
is not realy "hunting".  No offense.

Mega, if you do plan on going into paleontology as a profession, you would
do well to learn how to approach Science.  I and many others have been
trying to show you that paleontology is not about what feels cool or looks
the best on TV shows.  It is about using what limited evidence we have to
test hypotheses about extinct animals.  Sometimes the evidence supports our
hypotheses; sometimes it rejects them; often, there isn't enough data to
tell either way.

Again, I hope this helps.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661