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re: T.rex predation

At 09:59 AM 9/16/97 +0200, you wrote:
>I'm a little confused here: at what point does a hunter become a
>scavenger? What I mean is, a T-rex takes out a prey animal, and kills it
>(hunter). The animal is dead; T-rex takes a bite, and as far as the
>fossil evidence will show (teeth marks not healed by time) T-rex now
>looks like a scavenger.

By definition, predation is killing your own food; scavenging is eating food
which died by other means (possibly killed by some other animal, possibly
disease, injury, accident, starvation, etc.).

The vast majority of large (>5 kg) terrestrial tetrapod carnivores use both
predation and scavenging.

However, some paleontologists have suggested that Tyrannosaurus was an
obligate scavenger: that it was incapable of killing prey.  (For some on the
net, please note: THIS hypothesis has been suggested by certain prominent
hadrosaur workers.  Whether he believes it or not is not the issue: it is
the hypothesis of obligate scavenging which should be tested).

>So how do you determine which from the evidence?

If I tell you NOW, then why would anyone reading this want to go to DinoFest
next year? :-)

Okay, actually, many of the points I would bring up have been addressed by
several other posters on the net.  In addition, some of the technical
descriptions of key specimens or biomech analyses relating to this debate
are in press or in review, so let's wait until they are published before
discussing the details further.

However, I WILL leave off this puzzler (which has been alluded to already in
this discussion): how do you demonstrate that Tyrannosaurus (or any other
taxon) killed live prey?

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661