Re: Mammal competency.

[Robert.J.Meyerson@uwrf.edu (Rob Meyerson)]

>     Apart from the obvious blunder here (hedgehogs, badgers, and
>squirrels, for example, do seek eggs and when they find them they
>destroy them),

No blunder was made.  Sure they eat any egg they can find, but the
 amount of egg predation is not enough to threaten the bird populations
 in question.  In order for the hypothesis to be correct (that mammal
 predation destroyed dino populations), there would have to be a large
 number of mammals that *specialize* on eggs (IOW, eggs are their
 primary food source.  This seems highly improbable.

>     This is my position: Perhaps there were no specialist egg
>predators (but there may have been).  However, there may well
>have been mammal, bird, dinosaur, crocodile, lizard, and snake
>omnivores whose diet consisted, in a time when there _were_ more
>eggs, OF MORE EGGS!

It is improbable that these threats would be any greater in the
 Creatceous than they were previously.  These animals were around
 throughout the dinosaur reign, to no ill effect.  Unless of course
 there is a suggestion that all these groups got together with the
 desired goal of eliminating the dinosaur populations (conspiracy
 theories abound:-)

>Instead, it should be thought of as a
>gradual winding down of dinosaurs caused by the tipping of
>dinosaur reproduction from, say, level population growth, to
>slightly negative "growth".

Again, all the animals in question were with the dinos for most, and
 in some cases all, of the dino reign.  The ecosystems would've adapted
 relatively quickly to the threats, otherwise they would've died out as
 soon as they appeared.  Mammals appear in the fossil record at the
 same time as the dinos, if the mammals were any real threat, they
 would've had their impact right off the bat, and not some 200 my
 later.

>     Why mammals?  Tell me if this is right: Diversity data over
>the Cretaceous shows a gradual decline of dinosaurs along with an
>increase of mammals.  This doesn't prove causality, but it might
>be a hint.

Ecosystems are vastly complex mechanisms, so to say that a supposed
 decline in dino populations coinciding with a rise in mammal
 populations is related to one another is to oversimplify the problem
 (and there has probably been a lot missed).  One other interpretation
 of this is that as dino populations drop, the predation of small
 mammals also drops, allowing them to increase their numbers rapidly
 (the definition of an r-selected species) .

>One hour, two hours, a day?  Considering the bounty
>that is mine when I break through, how long is too long?  In this
>regard, can anyone suggest an analogue to a 4mm thick sauropod
>egg?

Any predator that can't take out the egg in less than a minute will
 not be successful, especially with all the parenting evidence that has
 been found.

>I believe it was the mammalian ability to plan and
>learn, their flexibility of response, that contributed most to
>their competency.

I think were beginning to get into the realm of anthropomorphising.
 There seems to be an expectation that these early mammals were as
 brainy as our species is.  Actually, most Late-K mammals stupid in
 comparison to the small theropods that were feeding on them.  If there
 has been any increase in brain activity, it is to avoid being a meal,
 rather than being a more effective egg stealer.

>     Given these abilities, we can think of mammals, towards the
>K/T, as being preadapted to take advantage of the dinosaurian
>egg.  These abilities evolved, not to exploit, but to avoid
>exploitation.  Nevertheless, for the dinosaurs it was a black day
>when the defences they had created were turned on themselves!

While the "David vs. Goliath" idea appeals to our emotions, it does
 not appeal to logic.  The only thing that these "abilities" helped was
 to keep the mammals from becoming extinct themselves at the hand of
 the dinosaurs (look up the concept of "refugia populations").

>Here is one: The hadrosaur herd settles down for the
>evening.  Up from a burrow near the egg beds, a group of small
>mammals creep, unseen, unheard, and unsmelled, amongst the egg
>beds.  Lapping from fluids released the previous night, or
>gnawing fresh holes, the group feeds quietly all night long.
>Before morning they return to their burrows, their stomachs full
>of rich lipids and proteins.

This one has Raptor Red written all over it: entertaining but
 illogical.  I have yet to hear of one mammal dentition that has the
 capacity for getting through the eggshell.  The only possible
 candidate would be the multis; but they had been around since the
 Jurassic.  If they were a threat, the dinos would've felt their
 presence long before the end of the Cretaceous.

(big snip)
>     Finally, my arguments have been based on biological causes
>for extinction.

Extinction doesn't just have biological causes.  Get a historical
 geology textbook, and look up the permo-triassic extinction: that one
 is more do with plate techtonics than biology.

Rob

***
"Perhaps if we made a large wooden badger."
        -MPATHG