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Re: sauropod breeding



On Sun, Mar 12, 2006 at 11:00:12PM +0100, David Marjanovic scripsit:
> >I'd like to ask the other people on the list how likely some of my ideas
> >about sauropod breeding are to be true or at least realistic. For purpose
> >of illustration the example I'm using is the Morrison fauna.  [...]
> 
> That all sounds very logical. But I just can't wrap my mind around a 
> precocial, free-living, independent sauropod baby. An animal of this size 
> that can't run, can't climb, can't swim as well as a lizard of the same 
> weight, and is not a turtle??? Even has isometric limb growth? How did 
> _any_ of them survive???

Well, you can probably assume highly cryptic colouring and a deeply
skittish nature, but consider sea turtles -- a quick google
http://www.hq.usace.army.mil/cepa/pubs/dec01/story11.htm -- finds
people talking about loggerhead turtles on the basis of a 70 year (30 to
100) female reproductive lifespan that involves laying as many as
100,000 eggs, nesting every 3 years and laying three to five clutches in
that year.

Of that 100,000, you get _two_ adults who themselves survive to
successfully breed in a stable population.

Given that predator numbers are set by the _minimum_ food supply, not
the peak food supply, interrupted nesting as in turtles would prevent
specialized egg predators from becoming established, and otherwise it's
just a whole lot of darwinian ammunition.  Sauropods could pretty easily
produce similar lifetime egg numbers.

Also note that the whip-tail sauropods and mace-tail sauropods probably
have these defensive measures from a small size, and that they'd apply
to equivalently sized predators just fine.  So Ornithosteles is fine
with the hatchlings, and maybe even the yearlings, but has some serious
cost-benefit concerns thereafter.