Re: And a cream pie in yours.

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

On Mon, 13 May 1996, Darren Naish wrote:

> Oh, silly me, what a blunder! Bar egg-eating snakes, all animals
> that eat eggs do so opportunistically. I'm not going to get involved
> in this debate, as I think it's an immediate non-starter. John might
> think me pig-headed but, well, that's science for you.

No, that's pig-headedness.  Science is when you do experiments,
experiments like this one by Thomas E. Martin (Bioscience, Sept. 1993
v43 n8).  Martin found that red squirrels, far from merely stumbling
on nests and eating the eggs, employ optimal foraging strategies.
Using artificial nests baited with quail eggs..."I put out 7 nests per
patch and varied the number of egg-containing nests in each patch
(one, three, or seven of the seven nests contained eggs).  Each of the
3 experimental treatments was represented by 10 patches. Predation
rates for any nest in a patch decreased with increases in the number
of nests that were unoccupied...Such results show that predators can
respond to numbers of unoccupied and occupied prey sites..."

> Are you really saying that egg predation was a major component in
> the extinction of dinosaurs?

I have a fundamental conviction that laying eggs, making nests in the
open-field is a bad idea.  Whether or not this liability _did_ kill
dinos, it would have eventually.

> Perhaps this explains the extinction of big ground birds in the late
> Tertiary too? (I'm kidding John).

Eggs were undoubtedly a liability to big post K/T birds and it
explains why there are so few of them around today.  Just one in all
of Africa, one in S.A., and several until recently in the small NZ.
Why?  To quote Eric Fuller's _Extinct Birds_: (Whose biggest chapter,
incidently, is on ratites) "...numbers and variety (of ratites) were
influenced by particular circumstances that applied to NZ but in no
other land of comparable size and equable climate.  Birds adapted to
niches normally occupied by mammals simply because there was no
competition from warm-blooded, four-legged beasts."

But this is to avoid the point of Darren's sarcasm. All I can do is
echo the standard response: when dinos died out, this left the
open-field niche vacant for birds who were better situated, in terms
of open-field predatory ability, than contemporaneous mammals.  Why
didn't the egg-predators, fresh from their victory over the dinosaurs,
dispatch the big birds instantly?  The dinosaur "economy" supported a
great range of living things, some or many of whom died when it
collapsed.  Then again, maybe the phorusrhacids had some better means
of protecting their eggs--but I can't imagine what.
        Another interesting question is: why didn't they eat all the
mammals above chicken size, just as the dinosaurs had done.  Perhaps
their numbers were kept down by as a consequence of a secret they
couldn't keep: the location of their eggs and babies!!!!!