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Re: Segregated vs age-mixed sauropod herds



On Sun, Mar 14, 2010 at 10:19 AM, Thomas R. Holtz, Jr. <tholtz@umd.edu> wrote:
> there are phylogenetic arguments (parental
> care for at least several weeks is present in crocs and birds, and hence
> in Archosauria ancestrally)

I was interested in a comment one of the news orgs. had re the snake
in the sauropod nests, that the dinosaurs probably did not attend the
nests allowing the snakes to help themselves. This speculation wasn't
in the paper; and I wonder is there any support for this idea?

I view it as very unlikely, not only from bracketing reasons, but
because sauropods laying eggs was a very big signal to would-be
predators. Predators must know where the eggs are; the nest must
therefore be defended.

My students wondered, then: why wouldn't the parents protect the
hatchlings from the snakes (I suppose this is where the non-attendance
assumption came from, i.e., if parents were there, they would have
killed the snakes!)?

I responded that while the parents were likely hanging around, they
had strict genetic rules that said: under no circumstances enter the
nest-ground proper...the risk of crushing babies being the strongest
selective pressure here.

The students said that was pretty stupid...that they could have leaned
over with their long necks and bitten the snakes.

I told them about fixed-action patterns in geese...the one in which
the goose has the rule: if there are any round things outside my nest,
roll them in...and how, if you take the egg away the goose continues
to roll air...that selection on this rule was stronger than any
pressure to consider contingencies. I said that one problem with
(relatively) small brains is the lack of flexibility in
decision-making...and that the sauropods were no more flexible in this
regard than the goose.

Anyway, the image of sauropod parents passively watching the snakes (3
in a 25m^2 area!!!!) devour their babies, haunts me (and my students)
to this day.