Re: group hunting

[Jonathon Woolf <jwoolf@erinet.com>]

Bill Adlam wrote:

> Jon W. wrote:
>

<snip>

> [Jaime said my T. rex idea]
> >> 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.
>
> I think that wolves have parallel hierarchies (male and female), like many
> primates.  In wolf packs it's usual for only the alpha male to breed, but
> also only the alpha female.  IIRC, only in particularly good years does a
> second or third female breed, but I'm not sure whether she mates with the
> alpha male or another one.  To summarise: lion prides contain many breeding
> females and few breeding males (and juveniles), wolf packs contain one
> breeding pair and many nonbreeding adults of both sexes.  Is that correct,
> Mr. Woolf?
>

That's pretty much right, except the alpha male dominates the entire
pack,
including the female hierarchy.  Wolves usually have one litter per pack
per
year, because one litter is usually all they can provide for even with
half a
dozen adults doing the hunting.

> >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.
>
> Additional halfway decent skeletons of T. rex and other theropods are needed
> to verify that the morphs are different sexes, and the robust ones are
> female.  But I don't expect a skeleton would need to be even halfway decent
> to judge whether it's robust or gracile.  Surely some fragmentary remains are
> diagnostic (of morph and to genus or preferably species)?
>

Some are, some aren't; it depends on what the fragments are, which bones
you have
fragments of.  Some bones can only identify general grouping -- 'some
sort of
theropod.'  Some are specific to the family level -- 'some kind of
tyrannosaurid.'  Some are diagnostic down to the genus and species level
--
'Tyrannosaurus, probably _T. rex_.'   And one of the problems with
classifying
fossils is that 'robust' and 'gracile' forms may be sexual dimorphism,
or it may
be a skeletal reflection of soft-tissue or behavioral differences that
mean you
have two species.

> Some pinnipeds, most notably elephant seals, have female-biased sex ratios at
> birth.  Besides, would you prefer a theory which only predicted what was
> already expected?
>

Humans have a biased sex ratio at birth too.  If I recall correctly,
it's about
5% in favor of girls, but differential survival rates mean that by
adulthood,
boys are a slight majority.  But that's a small difference either way, a
few
percentage points off 1:1.  No mammal seems to have a sex ratio that's
three or
four to one in favor of one sex.

-- Jon Woolf