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crocs eating hadrosaurs (was Gr. 9 sci proj)



Stephen Throop wrote:
>Paul Willis wrote:
>
>> Stephen Throop wrote:

>That brings up a question: how much did an edmontosaur weigh?  L B
>Halstead's reference book showed it at nine meters and implied a weight
>of three tons.  Lately I've been hearing it was 13 meters long.

Well, one of my books says 13 meters and 3.5 tonnes. Don't ask me why
the 9-meter one would be so heavy...
>
>I wasn't wondering if a croc would eat an edmontosaur.  I was wondering
>if a croc would hold his ground when he heard an animal of unknown size
>thundering toward him.  I think even grizzly bears often retreat in the
>face of threatening noise.  I think the footsteps of a large running
>biped could hit a croc hard enough to kill it.

I rather doubt that edmontosuars "thundered" everywhere. Unless being
pursued, I would imagine they sorta "moseyed" along -- not the sort of
approach that would scare a waiting hungry predator.
>
>> >If duckbills were as smart as crows, I think they'd be familiar with the
>> >haunts and habits of local crocs, be vigilant, and pass warnings.

You have a high regard for their intelligence and communication skills, sir.
>>
>> Codswallop. If humans (some being smarter than crows) can be taken by
>> crocs, why not hadrosaurs?  Zebra, wildebeast and buffalo live with the
>> nile crocodile and regularly form part of its diet.

I agree. Most animals that pass thru croc habitats regularly wind up as croc
food, at least occasionally.
>
>I speculate that duckbills were different from zebra, wildebeast, and
>buffalo.  I've read that, in their time, duckbills accounted for 75% of
>dinosaur herbivores.  They must have been doing something right.

This has no bearing, except to indicate that they were probably a LARGE
(75%?) part of the croc diet. What percentage of an African croc's diet is
formed by the top 75% of local herbivores?
        I've seen this sort of idea before -- that, because a species was
prolific,
it must have had good defenses against predators. By this logic, rabbits would
be invulnerable.
        What we're really looking at here is a species whose role is predator
fodder. Rabbits are prolific because they can: A) run, B) hide, and (most im-
portantly) C) BREED LIKE HELL. I realize edmontosaurs aren't rabbits, but if
you look at what is known of Maiasaur breeding (the best known hadrosaur
for that subject), it sure looks like they bred like hell. Giant nesting
grounds,
wall-to-wall with nests and mother dinos nose-to-tail. A nest Jack Horner re-
constructed had at least 23 eggs in it (see photo in _Digging Dinosaurs_, color
plate 7). Another nest was found with the remains of 15 hatchlings. If we can
assume that most hadrosaurs had similar habits (not a safe assumption, but
it's the only data I have), then edmontosaurs were also prolific breeders.
So when you say they were doing something right, what they were doing is
what any successful herbivore does: breed enough to balance predation.
>
>Don't humans regularly go into the waters of the Nile, the Everglades,
>and the Louisiana Bayous with very little chance of being eaten?  Aren't
>there animals that frequent crocodile waters but have little chance of
>being eaten?  How about panthers and manatees?  Are these waters
>inhabited only be crocs?

Manatees are saltwater animals, not freshwater like the American alligator.
The Florida Panther is another name for the cougar/puma/mountain lion, and
doesn't go swimming if it can help it. Humans who go into the bayous and
Everglades usually go in boats.
        It might interest you to know that in South America jaguars are known
to occasionally eat crocodiles. But in their habitat, crocs are the top
predator.
>
>> >Don't crows drive hawks and owls from an area by harassment?  Couldn't
>> >duckbills  also have used commotion and tooting to encourage big crocs
>> >to relocate?

Crows don't "think" like herbivores, because they're not. They are scavengers
and light predators, and closer to being competitors to hawks than prey.
        When was the last time you heard of rabbits driving wolves out of their
area?

Wayne Anderson