Re: Armadillos at the K/T!

["David Marjanovic" <david.marjanovic@gmx.at>]

> >...in all natural ecologies, the prescence of an egg-eater or
> > predator upon eggs or newly hatched young, or what have you, are part of
> an
> > equilibrium,
> > fluctuating between the extremes of too many prey, to many predators.
There
> > is no upset in this
> > equilibrium without the introduction of an alien prescence.
>
>  I don't think this statement can be made without examination.  First of
all
>  it assumes a steady state system--ecologies are certainly not this over
any
>  meaningful expanse of time (otherwise evolution would not be seen).
> [...]

OK, but you assume such a case of background extinction for not one species,
or maybe 10 around the globe, but hundreds or thousands at the same time
while nothing such happened during a long time before. This is IMHO even
more, a lot more, improbable than a steady-state ecology.

> Thirdly, while it makes good sense, predator/prey
>  oscillations around theoretical carrying capacity is illusive to test,
and I
>  know of no study which shows this to be the case.

I'm sure such studies exist. In school I had an example of an island in a
Canadian lake which was first populated by moose (in a severe winter, over
the ice); this population exploded and then crashed a few times. Later
wolves came in, but their population exploded only once (and much less
extremely), and then the famous fluctuations began.

> >We have used the bolide hypothesis to
> >suggest that catalyst to many disrupted ecologies from the Devonian on.
> > There is evidence for
> >this.
>
>  Evidence of impacts, yes.  None for direct causation, however.

Now come on. We can be 100 % certain that more than nothing will happen when
a 12-km-rock impacts aka 10,000 times all nuclear weapons of the world are
ignited at the same time on the same spot (without the effects of
radioactivity). It just _can't_ have left all non-neornithean dinosaurs
unaffected.

> >Egg-eating species are naturally in balance with their prey, such as
coatis
>  (there are animals
> >like jagarundis and cougars, even peccaries, that will, can, and have
> > [killed] coatis for their
> >predatory ravaging of the young. Never in a natural ecoogy to egg- or
> > young-feeders decimate a
> > population of prey.
>
>  Millions of species have become extinct over geological time.  We have a
>  fair idea of the causes of only a handful.  How can one claim extinction
is
>  _never_ due to predation on young.

True.
But to claim _mass_ extinction is due to predation on young is <looking for
the right adjective...> erm, bizarre.

> This is especially difficult to argue
>  when we realize that by far the most severe cause of mortality in many if
>  not most species is _predation on the young_.

Of mortality, maybe (in crocodiles it's AFAIK flooding of the eggs). Of
extinction?

> Also, "natural ecologies" are
>  the denumen of all previous struggles for survival.  Species that
couldn't
>  cope are gone!

So why don't we see progress in evolution?

> >The
> > mammals present which may have predated upon eggs or young (in the
> > Creataceous) are not of a size, sans *Mesodma* and
> > one or two other forms (as big as a badger, still smaller than most
> > effective extant nest-robber
>
> Badger-size is a threshold under (or around) which many offspring
> predators of today operate: hairy armadillo, caracara hawk, coatis,
> monitor lizards, skunks, squirrels, cats, rats, weasels, foxes...I could
> go on.

Nile monitors (famous for eating croc eggs) are AFAIK bigger... However,
where's the devastating effect of *Gobiconodon* all over Asia and North
America in the EK? (Just in case >:-> -- it was too early to have caused the
Cenomanian-Turonian event, which was AFAIK a more marine affair)

How common are the large Hell Creek mammals, BTW?