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Re: My Gr. 9 Science Fair Project: Questions



Paul Willis wrote:

> Although Deinosuchus material is incomplete and size estimates are hairy at
> best, they were certainly larger and heavier than any hadrosaur around
> them. In similar situations today, big croc do not get out of the way of
> smaller herbivores.

Well, okay.  Still, if a duckbill raced for the nearest water to escape
a tyrannosaur, it seems unlikely that it would happen to step on a
croc.  If the duckbill swam to get far from the tyrannosaur, could the
croc close the distance before the croc's anaerobic energy ran out?
>
> Are you assuming that duckbills were occur is large numbers because they
> had a system for avoiding being eaten by crocodiles? If so, you need to
> seriously consider the plethora of other factors that could be at play in
> the differential sucess of hadrosaurs as indicated by thier occurance in
> the fossil record. It is far more likely that they were out breeding their
> competitors or that, because they moved in hers, they are disproportionatly
> represented in fossil deposits or that their favoured habitats were closer
> to areas where fossilisation was likely to occur or that their breeding
> season more closely tied to environmental cycles that would favour
> fossilisation or that their are hydrodynamic factors that favour the
> preservation of hadrosaurs over other herbivores etc, etc, etc,.
> Interpreting apparent competative advantage based on relative occurances of
> species in the fossil record is a very tricky business.

Large concentrations of duckbills nested in conspicuous colonies long
enough for the young of one genus to hatch from 20-cm eggs and grow to
at least a meter.  Wasn't that a strategy of protecting a few offspring
rather than scattering many?  Even if duckbills were uncommon dinosaurs
who fooled us by being especially good at leaving fossils, losses had to
be controlled, and edmontosaurs lived in swamps.  (Should I trust what
I've read?)
>
> >Don't humans regularly go into the waters of the Nile, the Everglades,
> >and the Louisiana Bayous with very little chance of being eaten?
>
> For get humans for a start. We have complex behavioural structures lacking
> in other animals that can be used to avoid crocodile attacks (eg, Communal
> calls of "Get out of the water you bloody idiot, there are crocs in
> there").

The time I tried to shoot crows for my uncle, it was like the line from
"Butch Cassidy": "Who ARE those guys?"

Their sentry realized I was armed long before a human would have.  Like
a croc swimming underwater, I used the woods to stay out of sight as I
kept trying to get into range of the crows in the field.  The sentry
always anticipated where I would appear.  He'd greet me sarcastically,
and I'd see that the flock had already shifted just out of range.

Finally, I tried a shot from so far away that I aimed nine inches high.
Amazingly, I killed the crow.  The flock responded with contempt.  The
nearest ones moved a little farther away.  All continued pecking corn.
Now that they knew my range, I never got another shot.  They always
anticipated where I would appear and stayed just out of range, as if
defying me to try again.

Birds are used as models to speculate about dinosaurs.  If I were a
croc, I'd hate to be hunting dinosaurs if they were as smart as crows.

> All animals
> that come to the waters edge are fair game for the crocs (with one or two
> notable excaptions such as hippos). Carnivores such as various cats and
> monitor lizards have been seen to be taken by crocs.

I think the question is not whether crocs ate edmontosaurs, but whether
such incidents made it unfeasible for duckbills to enter the water.
Occasionally somebody manages to shoot a crow, but it doesn't seem
common enough to have much effect on the crow's long life expectancy,
and they don't avoid cornfields.

Thanks for your remarks.

- Stephen Throop