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RE: How Did Hadrosaurs Survive? (Was: Hadrosaur "mummy" questions)




From: "Williams, Tim" <TiJaWi@agron.iastate.edu>
To: "'Tim Donovan '" <msdonovan66@hotmail.com>
CC: "'dinosaur@usc.edu'" <dinosaur@usc.edu>
Subject: RE: How Did Hadrosaurs Survive? (Was: Hadrosaur "mummy" questions)
Date: Tue, 29 Oct 2002 14:00:30 -0600

Tim Donovan wrote:

> Baby hadrosaurs weren't worthwhile prey for tyrannosaurs. Troodont
> teeth have been found in association with hadrosaur nests, but no
> tyrannosaur teeth AFAIK.


Yeah, but according to your scenario Mommy and Daddy were targeted by adult _Tyrannosaur rex_. What does Mommy Hadrosaur do when a tyrannosaur sees it sitting atop a nest, or feeding its nestlings? - run, and leave her babies to their own devices.

Unfortunately the adult hadrosaurs would probably only get themselves killed. A single bite from a T. rex could cause fatal bleeding as GSP pointed out. Not that tyrannosars were likely to attack nesting areas often. The adults would flee along with any juveniles old enough to, leaving tiny hatchlings. Sure tyrannosaurs might've eaten them occasionally but generally they had to go after larger, worthwhile prey.





Maybe hatchling hadrosaurs made wonderful prey for hatchling tyrannosaurs.

Read THE COMPLETE DINOSAUR. P. Currie attributed the great diversity of small theropods in the LK to tyrannosaur adults feeding their young, leaving other niches open to other theropods, notably the nest raider niches.



Maybe adult tyrannosaurs ate baby hadrosaurs as a light snack.  Either way,
adult tyrannosaurs would probably not have shed teeth engaging a hadrosaur
hatchling.

But they probably would have if adults defended the nest.


The above scenarios are speculative. But you see, these scenarios cannot be
refuted,

But are dubious.

and they offer an alternative to your "concrete" assertions on
tyrannosaur behavior

Not a very credible one.



Bottom line: We don't know enough (and probably will *never* know) to reconstruct the behavior of tyrannosaurs in the type of detail you're offering.

I disagree.


> But titanosaurs were armored,

Some were; maybe not all titanosaurs were armored, however.

The smaller ones, most likely to be targeted e.g. Saltasaurus, definitely were.

> hadrosaurs were not. Unless an herbivore is gigantic, it should have armor


> or weapons if it attempted to stand its ground.

Again, you do not *know* this.  I'll repeat what I said: large size is a
potential *deterrence* against large predators.

But hadrosaurs were not sufficiently large in relation to tyrannosaurs for a combative survival strategy to be credible in the absence of armor or weapons.




The massive strength of a
hadrosaur fighting for its very survival is enough to *injure* an attacking
tyrannosaur.

Possibly, but the tyrannosaur had an advantage-it was clearly designed to fight and kill, the hadrosaur was not. Lacking weapons, but evolving hooves and keen senses, hadrosaurs would have fled, and fought only as a last resort.



An injured tyrannosaur is as good as dead if it can't chase
and bring down prey any more - and you yourself has argued that these guys
were fast predators.  No tyrannosaur would want to risk serious and
debilitating injury.

Lions are occasionally injured and bereft of their ability to hunt, but they still prey upon healthy adult ungulates.



Much better to target old, young or sick individuals -
those least able to fight back - as Cliff said.

There is evidence that tyrannosaurs attacked armored dinosaurs, and perhaps ceratopsids, which are much more dangerous or tougher than hadrosaurs. Also, if tyrannosaurs did not dare attack healthy adults, why did ceratopsids and ankylosaurs evolve greater size to match T. rex? The average adult size should not have changed if they were generally not targeted.



> What hadrosaur would be foolish enough to fight a predator of > comparable size without any obvious weapons?

Ummm.... any hadrosaur that wants to stay alive

would run away as fast as possible!

Pretty good advice I'd
say.


Tim Donovan


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