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

[Jonathon Woolf <jwoolf@erinet.com>]

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.