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Re: Differential reproductive failure of dinosaurs



On Sun, 21 Apr 1996, Dalmiro wrote:

> This thread is starting to bother me, we have evidence suggesting that
> dinos didn't have a big problem with egg predation, the recent
> oviraptor found had a huge number of eggs with him, and the brooding
> colonies of other dinosaurs don't seem to have an egg
> shortage.

This simply reflects the fact that dinos dominated the open-field niche
for millions of years, which we already know.

> Finally it will be hard to
> explain how the nasty mammal egg
> eaters managed to eliminate dinos in places like Australia and New
> Zealand, The Americas, Europe Asia and Africa at roughly the same
> time.
See response to Derek Smith.

> Egg laying and brooding occurs over a small time interval, the
> predators will have to survive on other food sources for most of the
> year...

In an even climate, different dinos lay at different times (like fruits
in a tropical rain forest).  An Orangutang eats many different fig sp.
But they all fruit at different times.  The Orang has a gardeners
knowledge of when and where these are.  Even simple animals evolve highly
elaborate optimal foraging tactics.  But most likely the mammals in
question were omnivorous...

> and brooding in colonies makes it almost impossible for the
> predators on that area to eat all the eggs...

.eat from the outside in.  Soon the big colony becomes a small colony..

>the
>main problem has to
> do with predation on young, yet I fail to see what's the big mammalian
> advantage on having a few big expensive youngsters, dinos had lots of
> small and cheap hatchlings.

.K or r selected species both may do well.  The terms are also
relative, i.e., one sp. K is another's r.  Look at us.  We are K
selected and yet we are increasing exponentially.  We have a few
_very_ expensive youngsters, but, because we bring them all to
reproduction, we do well.  The dinos may have had many more
hatchlings, but they were on their own.  No doubt there were
specialist hatchling predators (notwithstanding T. Holtz'
comments-maybe birds were contenders here...

)Predators and many small
mammals
give > birth to altricial offspring, wich are at no better situation than
> eggs.

Altricial marsupials ride with the mother: the eggs stay put.
Altricial puppies are closer to maturity than a fresh egg!  Less time to
maturity means less predator alerting trips to the den.  Besides,
burrowing provides a security that altricial or not, dino hatchlings
didn't have.