*****SPAM***** Tyrannosaurus "Scavenger vs. Predator" debate - Some questions for Dr. Jack Horner:

["Vlad Petnicki" <bucketfoot-al@justice.com>]

I believe that Dr. Horner?s theory that T-Rex was
primarily a scavenger is:

a. contradicted by direct evidence; and

b. fails a logical analysis that I recently
brainstormed while taking a long drive (when I have
traditionally done some of my best thinking).  More on
this in a moment, but first, the evidence.

A.  Direct Evidence of predation in T-Rex:

Recently I became aware of two fossils that show
wounds that indicate tooth marks and bite
circumference of adult T-Rexes; in both instances the
prey escaped and the wounds healed.

The first is a complete Anatotitan skeleton
(I believe it might be at the Tyrrell Museum, but don't
quote me here - I saw photos of it on one museum site
recently).  The amazing part is a large circular bite
that removed, in a perfect semi-circle, portions of
several tail vertebrae, along with marks and holes
fitting T-rex teeth perfectly. The animal's wound
healed.

Secondly, I just recently read a description of a
Triceratops skull with teeth marks on the frill - and
on one broken horn; again, matching T-Rex teeth
perfectly.  Again, the animal lived and the wounds
healed.

Several points here;  with most fossils bearing T-rex
tooth marks, it is not possible to say how the animal
died, or what animal killed it - it is only in the very
rare instances of grievous injury, followed by healing,
evidenced by these two fossils, that we get a clue. 
The fact that several of these exceedingly rare fossils
have been found would tend to suggest that this was not
a unique occurrence.

Now, my information is that there is no other large
predator known from Hell Creek - except for T-rex.  The
next largest one is, I believe, a 6-foot Dromaeosaur.

This fact indicates that T-rex is the only known animal
that could have inflicted the wounds described above.

This point about the Hell Creek predator records leads
me to my second point of logical analysis, which
occurred to me during my "brainstorm".

B. Logical analysis of Hell Creek fauna/ecosystem;

Since T-Rex is the only large predator known from Hell
Creek, a problem exists for the theory of T-rex
being an exclusive scavenger.  

For the sake of argument, let us take as correct Dr.
Horner?s view that a T-Rex adult was too heavy, too
slow, and too near-sighted to be anything but a
scavenger(One question on this last point - would not
the measurable fact that T-Rex's eyes faced forward,
thus allowing for stereoscopic vision, contradict that
part of Dr. Horner?s analysis?);

So, let's look at the ecosystem it lived in.  

If T-Rex was indeed a scavenger, how is it possible
that no (other)large "predator" is known from 100+
years of excavating at Hell Creek?  Doesn't nature
abhor a vacuum? If T-rex was not a predatory animal in
the main, where is that "other" "Apex predator" in this
ecosystem?  Why is that niche empty?

Logically, a scavenger eats other animals' kills.  It
surely cannot survive by mainly waiting for prey to
keel over from old age.  But if an adult T-rex was a
scavenger, what other animal's kills did it scavenge if
the next largest meat-eater known from the site is a
small Dromeaosaur?

Let us now offer several possibilities that would get
us out of this quandary, and perhaps to a point where
we may come to some agreement with Dr. Horner on this
issue.

Several recently described skeletons of sub-adult and
juvenile Tyrannosaurids indicate that, while the main
"weaponry" in terms of the jaws and teeth was fully
developed early in life, the younger animals were
lighter, with longer legs vs body ratio - in short
built for speed.  

If T-rex was primarily a scavenger, would not these
youngsters have starved to death because the much
larger, older adults would have monopolized the
carrion?  They didn't, and the reason is obvious from
their physiology.  They were not scavengers.  They were
the 'Apex Predators' of that ecosystem.

Now, we can concede the argument that adult T-Rexes may
have relied on scavenging more than on predation, but
they would have been scavenging the kills of their
lighter, younger, predatory offspring.  Is that the
whole story?

Perhaps.  Since no terrestrial animal known is an
exclusive scavenger, perhaps whether it mainly preyed
or mainly scavenged was a factor of its period of life
(age), rather than a factor of its species.

A second, as yet unproved theory, is that of pack
hunting, where the above described differences between
individuals, based upon their age, would have fit with
and complemented each other.  We know that the giant
Allosaurids from South America appear to have lived in
packs (which the two Giganotosaur burial groups found
by Dr. Coria indicate - indeed, given the size of the
Titanosaurids down South, this makes logical sense -
prey bigger than predator drives pack hunting; predator
bigger than prey drives solo hunting).

I believe that one mass Albertosaur grave was found in
Canada, suggesting that this close relative of
T-rex may have done likewise.  Younger animals chasing
down, tiring out, cornering larger prey, til the
slower, more powerful adults caught up and
killed it (or ambushed it).

Surprisingly, this is not so far-fetched;  we know that
Crocodiles - arguably "dumber" animals than these giant
theropods - cooperate in predation in several ways -
several will hold an animal carcass under water while
one twists in order to tear off chunks of the prey;
then switching roles and taking turns 'sharing' the
kill; also, Crocs will often corner fish in a lagoon,
and block the only exit, then take turns, one by one,
going into the lagoon and feeding.  It is
well-accepted, as I understand it, that small brain
size does not necessarily prohibit complex herding or
cooperative behavior.

As was discussed on this site a couple of years back,
the very end of the Cretaceous in Western North America
has offered us some tantalizing clues as to the
existence of potentially 15-20 ton Ceratopsians
(Barnum's Maximum Triceratops fossil, and the
rumored-but-yet-undescribed 9-10 foot Triceratops skull
in the BYU basement that Dr. Bakker is familiar with
come to mind), as well as potentially 20-30 ton
Hadrosaurs.
 
Part of this is based on fragmentary fossil evidence,
but also on some truly huge Ceratopsian and Hadrosaur
tracks that have been discovered in North America.

So, T-Rex would have had a "choice" that we have seen
exercised everywhere else in the fossil record, where
prey grew bigger and bigger (Africa, South America,
Jurassic North America) - to get bigger too ? or to
pack hunt.  In any event, even an animal the size of
the "Celeste" Rex probably could not have
single-handedly taken on a 15 ton triceratops.

Therefore, it is tantalizing to speculate that perhaps,
like their distant Southern Continental cousins, T-Rex
may also have solved this problem by cooperating and
hunting in packs, or prides, where the animals' role in
the hunt would be dictated by its age and size.

These meanderings aside, if Dr. Horner wishes to defeat
the T-Rex-as-predator argument, he must not only take
down Prof Holtz's (and others) observations about the
massive power of the T-Rex dentary equipment,
suggesting predation, but he must also address the
logical problems with his theory, when viewed from a
"macroecosystemic" view that I have discussed above. 

In short, if T-Rex was indeed just a scavenger,
where is the missing "Apex Predator" from Hell Creek?

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