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Re: Segregated vs age-mixed sauropod herds



On Sun, Mar 14, 2010 at 11:50 PM, Jura <pristichampsus@yahoo.com> wrote:
> While true for some species, arribada species (the Ridleys) nest along 
> shorelines in Mexico. Plenty of predators to go around there.

As far as I can tell (Googling) prime beaches are actually sand bars.
>From South Padre Island, south into Mexico, Barro this, and Barro
that. Predator density is lower on these islands of sand.

> But this is what we see in sauropods. They were r-selected animals. Perhaps 
> moreso than most dinosaurs. The auca mahuevo nests also suggest that mass 
> nesting occurred in sauropods. While these could have been nests that were 
> tended by mothers, they also could have been group gatherings to suitable 
> nest sites; done partly to overwhelm would-be predators.

True...but we are not talking about hundreds of eggs/mother...I'm
arguing that _relative_ to sea turtles, the Titanosaurs were K
selected. Turtles overwhelm predators...Titanosaurs could have set up
colonies for nest defence: safety in numbers just the same.

> Reptile studies (lizard studies in particular) seem to show that clades can 
> evolve more, and less parental care depending on the situation.

But you don't see lizards setting up creches (ostriches), arranging
multi-generational nest provisioning (crows), guarding offspring
through different growth phases (alligators), or teaching their young
how to compete in the global economy (community college adjunct
professors)...I'm saying that there are small differences among
clades, big differences between clades, and increasing complexity and
flexibility among clades with larger brains...and that this potential
goes to titanosaurs more than sea turtles.

> I can definitely see sauropods evolving to be less parental than other 
> dinosaurs; likely for the same reason that crocs are still R-strategists 
> despite their extensive parental investments. It's very hard for a huge 
> multi-tonne parent to guard offspring that are many thousands of times 
> smaller than them.

It may well be that they were less nurturing...and, after all,
guarding a nest doesn't take that much parental skill. But I disagree
about the guarding problem. If, as I have hypothesized, there were
strict behavioral/genetic rules about going onto the actual nest
grounds, the parents could well have posted sentry around the location
and fended off theropods. Snakes were a different matter.