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Re: group hunting (was Scavenger vs. Predator Argument)

Jaime Headden wrote:

> <The gracile and robust morphs probably represent different sexes, and
> the robust ones are probably females.  I would guess the difference in
> size and strength was similar to that in lions, but with the females
> bigger. I'm sure someone on the list is familiar enough with both to
> correct me.>
> Nope, you're correct on the lion thing. But ... robust forms in dinosaur
> may mean what robust forms in crocs means, which is robust, smaller
> males and gracile, larger females. But we have robust, larger (?) and
> gracile, smaller (?). Birds have bigger females, like crocs, but there
> is little in the way of robustity as opposed to gracility. When Paul
> Willis gets back, he might be able to help with this particular part.

There's also the fact that the degree of dimorphism varies among different
species.  Some bird species have larger females.  A few have noticeably
larger males.  And many show no significant dimorphism, male and female so
similar that you have to examine them close up to tell them apart.  IIRC,
there's a correlation between the degree of dimorphism and the degree to
which care of the nest and young is shared.

> <If young males stayed with their natal pride, they would probably be
> too weak at first to have access to the breeding females. They would be
> able to help raise younger siblings, half-siblings, cousins, etc..>
> Sounds like wolves and hyenas, who are matriarchal in hierarchy.

Hyenas are matriarchal, but wolves are not.  A wolf pack is dominated by the
alpha male, and male wolves are decidedly larger than females.

> <Armed with this theory I predict a strongly male-biased sex ratio in T.
> rex. And sure enough, there is.>
> Unless you got the sexes confused (cf. above).

Or unless there's more to the matter than we think.  We have what -- a dozen
halfway decent rex skeletons known?  Maybe fifteen?  Not much of a
population base to be speculating on.  Especially not when I can't think of
any mammal species that has an M/F sex ratio that's noticeably off 1:1.  Not
every male ever gets to mate, but there are more or less as many males as
females born.

My $.02 worth, for whatever it's worth.

-- Jon W.