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Re: Segregated vs age-mixed sauropod herds



On Sun, Mar 14, 2010 at 9:56 PM, Jura <pristichampsus@yahoo.com> wrote:
> --- On Sun, 3/14/10, John Bois <mjohn.bois@gmail.com> wrote:
>> 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.
>
> +++++++++++++++++++++++++++++++++++++
>
> I don't follow. Sea turtle arribadas are also big signals to predators, yet 
> those nests go unattended (they pretty much have to, given the lifestyle of 
> sea turtles). Barring the recent advent of exploitative hominids, this 
> strategy seems to work just fine for them.

Sauropods and their nests were many times bigger than sea turtles.
Many (most?) sea turtles lay their eggs at night--I don't know if this
would be practical for a Titanosaur! Many of the prime nesting sites
for sea turtles are on islands remote from most predators...I don't
know that any dinosaurs had abilities that would have afforded them
the same separation from their predators. In addition, one of the key
factors in sea turtle hatching success would seem to be the massive
numbers of both mothers and eggs. Aren't they the classic example of
predator-swamping (at least in places where they have predators)? Some
sea turtles have clutches of between 100 and 200 eggs. At this rate,
the ocean would be thick with sea turtles if not for the intense
predation on hatchlings. Such profligate reproduction would not be
possible for sauropods. In any case, the trend in amniotes seems to be
toward the evolution of more not less parental investment in
offspring--or, should I say, investment in fewer high quality babies.
This makes nest-guarding more of an imperative.