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Re: Tyrannosaur age-population distributions




On Sun, 16 Jul 2006 08:46:02 -0400 Graydon <oak@uniserve.com> writes:
> On Sat, Jul 15, 2006 at 08:53:39PM +0000, Phillip Bigelow scripsit:
> [snip]
> > Sadly, in _T. rex_'s case, the animals usually died only a few 
> years
> > after they first experience the "wonders of procreation".  Not to
> > mention having to endure the hassle of being attacked and beaten 
> up on
> > a nearly daily basis after you reach adulthood.


> The other thing this does is make a hash out of pack-forming;


Not necessarily.  But it may give insight into the nature of tyrannosaur
pack-forming (if it existed at all).


> the
> breeding pair doesn't last long enough to raise their own offspring, 
> so
> how does the pack form?


Pack-forming may still have been an important part of _T. rex_ behavior,
but it may have occured only part of the year.  Alternatively, pack
behavior may have been the norm for most of the year, except for a short
period where mate selection was taking place (when all of those injuries
in the adults may have accrued).


 
> Currie, et al., still have pretty good evidence of pack behaviour 
> in
> Albertosaurs, with juveniles and sexually mature individuals in the 
> same
> group.

I realize that Currie and others have published a lot on this, but I'd
like to see even more data.  There is still the possibility that
taphonomic concentration was occuring.


> Did Albertosaurs have a different growth cycle?


Apparently, yes.  According to Erikson et al. (2004), p. 774, fig. 2, the
_Albertosaurus_ growth curve was shallower (lower-angle slope); with a
much less obvious "growth spurt" phase within the longer-period juvenile
phase; but with a similar [end of childhood -- beginning of juvenile
years] transition point.  This _Albertosaur_ childhood-juvie transition,
like T. rex, occurred around age 10 or so.

In summary, the entire _Albertosaurus_ grow curve is more subdued that
that of _T. rex_.


> Were tyranosaurine
> sibling bonds exceptionally strong?


In the juveniles?  Maybe.  According to the new paper that came out just
last week, juveniles led relatively "safe" lives up to about age 20 (body
bags for the juvies are almost non-existant).  So perhaps the youngun's
didn't hurt each other.  Their longevity also suggests (weakly) that the
juvies didn't hunt dangerous prey.  Perhaps they raided baby nests or
scavenged carcasses.



> Strong enough to work over 
> several
> years worth of siblings, so that the oldest had the help of their
> younger siblings in managing to breed?


Sort of like the Wilson brothers (the actors) all going to a singles bar
together and fixing each other up with dates?  ;-)


> Were tyrannosaurine packs
> accreted on a basis of purely social bonds?


Heh.  Keep in mind the size of a tyrannosaurid's brain.  IF pack
activities occured, was it instinctual?  Yes.  Instinct usually drives
behavior in non-mammalian vertebrates.  But was it "social" behavior,
sensu lion prides?  Who knows, but I doubt it.


> I have no idea how to answer those questions, but I sure hope 
> someone
> does.


Hey, don't look at me.  I just sweep the floors and empty the garbage
cans around here.

<pb>
--
Why do chicken coops only have two doors?
Because if they had four doors, they would be chicken sedans.
(as told to me by my neighbor's son)