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Re: Nesting strategies (was Big = Old = Advanced?)



Rob Meyerson wrote:
> 
> Bryan R. Stahl writes;
> 
> >But would it follow the wolf - coyote pattern, or would it take an African
> >style pattern, i.e. lion - jackal, hyena - cheetah, or lion - hyena?  The
> >wolf - coyote pattern would seem to apply to the different species of
> >tyranosaurids,  with the smaller being driven into more marginal areas by
> >the larger.  The African pattern seems closer to the dromeosaur -
> >tyrannosaur idea.  The idea being, would they directly compete like lions
> >and hyenas(which ever side has the advantage driving the others off), would
> >the dromaeosaurs scavenge like jackals, or would the tyrannosaurs plunder
> >the dromaeosaur kills like hyenas and lions do to cheetahs?
> 
> To start off, let's define each of the patterns you recognize.  The 
> lion-jackal
> pattern is where the smaller species tends to come in after the big one has
> finished with it's kill.  The hyena-cheetah pattern is the exact opposite,
> larger species stealing the smaller species kill, so let's consider this to be
> the flip side of the same coin.  The lion-hyena pattern deals with two species
> that are evenly matched in size, strength, and power.

This isn't quite accurate; spotted hyenas and cheetahs are about the
same mass (40-86 kg and 35-72 kg respectively) while hyenas and lions
are extremely different in size (40-86 kg and 82-120 kg (females),
respectively).  Both hyenas and lions get away with stealing food from
cheetahs not because the cheetahs are too small to fight back but rather
because they have a pathological fear of fighting.  They won't do it,
even if they have a good chance of winning.  Hyenas and lions face off
not because they're matched in size and strength but rather because the
hyaenas run in larger packs and are extremely aggressive (spotted
hyenas, mind you; totally different story with the smaller striped and
brown hyenas).
 
>  In a Cretaceous setting, the hyena-cheetah pattern would fit best with 
> tyrannosaurs and dromaeosaurs.  The smaller theropods would most likely 
> be driven off a kill by the larger theropod.  I'm not sure what, if any, 
> effect
> that pack living would have on this pattern, but I suspect that even a good
> sized flock would be driven off by the tyrannosaur (is it safe to assume that
> there was an inverse relationship between the size of the pack and the size of
> the species?).  

This is a dangerous assumption; first, your model is probably not
terribly accurate.  The hyena-cheetah pattern certainly can't be taken
to be typical of anything, given the fact that cheetahs are so
dysfunctional and hyenas are so abnormally aggressive.  Second, hyenas
are consistently social while cheetahs are  not (consistent, that is),
whereas Dromaeosaurs were likely social and Tyrannosaurs were likely (or
not?) not social.  Second, there's no reason to think the larger
predator (solitary predator, mind you) would necessarily drive off the
smaller (and remember that we still don't know if T-Rex *was* a
predator; I don't think Horner's ideas have been conclusively
overturned, have they?); think bears and wolves (a much better analogy,
IMO), wherein who gets driven off depends on the mood of the bear and
how many wolves decide to take it on.  

Regarding animal size and pack size: I'm not aware of any studies done
on it, but my gut reaction would be the there's no relationship
whatsoever.  Wolves are the most social of canids; they're also the
biggest.  Lions are the most social of the cats; they're also (aside
from tigers) the biggest.  Spotted hyenas are just weird, having a sort
of fission-fusion grouping that's hard to classify (though the other
species are much less social, typically small family groups).  It's
really hard to generalize when it comes to animal sociality.

Any analogies here are going to be pretty flawed, as we're talking about
a predator/scavenger the size of an elephant and a predator the size of
a dog.  We don't really have anything to compare that to, at least among
modern mammals or birds.  

> The way that the lion-hyena pattern would come into play is if there 
> were two species of tyrannosaur, or a tyrannosaur and an albertosaur,
> living in the same area.

I definitely agree here, though you might have skittish tyrannosaurs
which would make the lion/hyena-cheetah pattern workable.  Alternately,
you might have had pack-living tyrannosaurs, which would make the
lion-hyena pattern feasible.  In this case, I would think the Dromies
would just get the heck outta dodge.  :)
 
> I suspect that each species of the larger theropod, or each individual/pair 
> bond
> (depending on your viewpoint), had a distinct home range that could be easily
> defined.  How the smaller theropods related to this is anyone's guess.  The
> smaller theropod could pose a serious threat to the larger theropod's chicks,
> and so the smaller ones would be driven off.  Then again, if the food supply 
> was high enough, the larger theropods might tolerate the presence of the 
> smaller 
> ones (especially the troodontids).  There is also a question of whether the 
> two 
> species operated under different niches, which would cut down on how they 
> related 
> to each other; perhaps some dromaeosaurs specialized in scavanging.

This last part's particularly relevant; we know next to nothing about
the niches these animals created for themselves.  For all we know, they
might have been like wolves and mountain lions, predators in the same
ecosystem which rarely, if ever, interacted.
 
Chris