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RE: T. rex

        The categorical distinction "predator" vs. "scavenger" doesn't
to be a very sharp one, as the discussion of hyenas vs lions shows. There
is now plenty of footage by Hugo Van Lawick and others showing hyenas
killing and then being driven away from their kills by lions. Lions also
steal from Cheetahs. On the other hand, hyenas are known to eat things
so dead that only the bones are left. Their powerful jaws can crack the
largest bones and extract the marrow from dessicated carcases. When Dr.
describes T. Rex as a scavenger, "like hyenas", as he has done, it is
not clear whether he means the complex of behaviors now known as
part of the hyena repertoire or the old, naive view of hyenas as the lowlife
of the the veldt. Eating fresh kills by other animals is still scavenging,
and killing by lying in wait, taking a bite out of something and then
letting it die from bloodloss so you can eat it at leisure is still
Predation and scavenging are each complex terms that describe behavior 
patterns, not lifestyles.  Animals may easily switch from one behavior
pattern to another depending on availability of food sources, time of year,
and even personal preference. Large brown bears feeding on salmon adopt
a wide variety of fishing styles, including diving to the bottom and eating
the dead salmon who have already bred. The same species, on the same
river, at the same time, includes bears stealing from other bears, bears 
fishing with their mouths open in the current, bears swatting salmon with 
their paws, and bears diving to the bottom for the fresh dead fish.
        I worked on a fossil bed in Canada, on a dig organized by the RTM.
In addition to Edmontosaurus bones, among the most common fossils
were Albertosaurus teeth. There were also Edmontosaurus bones modified
by Albertosaurus teeth. There is little doubt that this was a secondary
deposition from something like a large river-crossing death site which
had been scavenged by the big carnivores. A large source of corpses like
this could have provided many large carnivores with enough body fat reserves
to last through a winter, if it occurred in fall, especially if they slowed
their metabolisms during cold weather. And yet, the same species
could have exhibited complex hunting behavior.
-G. Derkits 
> ----------
> From:         Derek Tearne[SMTP:derek@url.co.nz]
> Sent:         Sunday, March 07, 1999 6:41 PM
> To:   dinosaur@usc.edu
> Subject:      Re: T. rex
> At 19:02 -0500 5/3/1999, Sara Burch wrote:
> >I am certainly not a T. rex expert, but here's a thought. Lions will
> certainly
> >take a piece of dead meat if it's available, and hyenas will hunt down
> prey if
> >they can't scavenge.
> I think it has been shown recently that Hyenas are in fact adept hunters
> and
> don't scavenge much more than Lions do.  It seems a lot of the 'Lion
> Kills'
> that the Hyenas were thought to be scavenging are in fact Hyena kills that
> the Lions have moved in on.
> >T. rex would probably have taken dead meat, as well as it would have
> hunted.
> Being the biggest thing with sharp pointy teeth around it could easily
> have chased smaller predators away from their kills like Lions do today
> whenever they can.  Lions do hunt very effectively though, and
> any features of T.rex that make it a good scavenger (such as a good
> sense of smell) would also help make it a good hunter.
> I'd say it was a hunter that scavenged whenever it could - just
> like all terrestrial hunters today.  Is there any predator that
> *doesn't* scavenge when it can?
> --- Derek
> ---
> Derek Tearne.   ---   @URL Internet Consultants  ---  http://url.co.nz/
> Some of the more environmentally aware dinosaurs were worried about the
> consequences of an accident with the new Iridium enriched fusion reactor.
> "If it goes off only the cockroaches and mammals will survive..." they
> said.