Re: gigantism as liability

[john bois <jbois@verizon.net>]

----- Original Message ----- 
From: "Graydon" <oak@uniserve.com>
> Consider sea-turtles; no parental care, young born very small and having
> to spring down the beach to the water. Most don't make it, and must then
> get through many years in the ocean to reach breeding size.  Yet, absent
> humans, turtles do very well.
>
> Perhaps the essential thing was staying alive as an adult long enough to
> lay enough eggs.  That would make predator defence through size a
> component of the r-strategy.

But turtles have additional predator defences: a tough shell...meaning that
increasing thickness of shell led to decreasing number of potential
predators. Rather than enjoying such incremental predator-immunity, each 
cohort of sauropods would be greeted by a new guild of predators. Turtles 
have a defensive strategy; I'm only arguing that sauropods must have had one 
too.

> Because being really big means really strong reproductive constraints if
> you're a mammal.  One offspring every five years is not robust over
> evolutionary time.

Is there actually a constraint on producing 5 smaller babies?

> Sauropod nest defence has to explain how it could happen; 2 kg verses 20
> tons is four orders of magnitude size difference.

Not sure what you mean here...

> There's _three_ orders of magnitude between the adult and the probable
> predators; how well would you expect rhinos to do, guarding against
> foxes?

There are plenty of examples of small predators picking on large...mice on
albatross, armadillos on rhea, black-backed jackal on ostrich, monitor 
lizards on Nile crocs.