Re: Big = Old = Advanced?

[John Bois <jbois@umd5.umd.edu>]

On Mon, 25 Aug 1997, Jeffrey Martz wrote:
John Bois:
> > culling going on. Laying more eggs would seem to be a fruitless
> > enterprise.  

J.M.:
>        If the environment, by predation, illness or other factors, has
> the capacity to kill X number of offspring, you want to produce MORE then
> X number of offspring so enough will survive to maturity to continue the
> species.        

I don't disagree with anything you say.  What I meant by saying the
dinosaur shouldn't lay excess is this.  Given the following options:  if
she lays 5 eggs and only one reaches maturity; if she lays 10 and 3 live;
if she lays 18 and 5 live; if she lays 25 and 5 live; if she lays 70 and
five live; given these alternate strategies she should probably lay 18
eggs.  To lay more is a waste.  And this is true no matter how big she
is.  My point is that it pays at least some layers to be frugal.  Species
that are long lived shouldn't bust a gut the first time around by going
for the big semelparous bang.  This was in response to Dinogeorge's point
that 18 was not a big clutch size for such a big animal.  My response was
that magnitude of clutch is strictly relative, not to size, but to life
history.   


>      Previously in this discussion, you suggested that r startegies make
> little sense, because a parent would not feel complelled or obligated to
> feed predators.  

I can't imagine I would say such a foolish thing. r strategies make
perfect sense to a species whose offspring must attempt a try at the
plankton sweepstakes, for example.

> This is missing the point; the predators will take as
> much as they want, if they can.  Taking really good care of your offspring
> is only possible of you have few.  The more you have, the more you are
> spreading yourself thin defending them all, and therefore the more
> predators will take.  Or, looking at it another way, if the predators will
> take a lot, produce even more. 

This was back on predator satiation thread, right?  I think my problem
with this idea is more semantic than anything else.  I just don't think
they prey are trying to satiate the predators, morlock style.  It might
begin like this: a herbivore lays its eggs in a place of low predator
density.  She achieves reproductive success.  She and her conspecifics
thrive in this place.  Local predators start preying on them and they
repond by upping clutch size.  The resource (eggs and hatchlings) is now
so bountiful that local predators cannot eat it all.  And some sort of
equilibrium is reached.

But my point with dinosaurs is that they could not have as big a skill
differential as modern prey and their predators.  Sorry to repeat, but a
goose can leave its home predators in the dust, while, for all we know,
hadrosaurs brought every single predator with them.  No, this doesn't
happen very much in modern migrating herds.  But these are not analagous
to migrating dinos because they can carry baby around until its ready to
run itself.