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Re: Tyrannosaurid Growth Spurts



Kris Kripchak (MariusRomanus@aol.com) wrote:

<Well yes. I mentioned that. Here's another way to view it: We can't all
live in a protective bubble now can we? Just because we like to walk
around in pillow armor doesn't mean everything else does. I think that
Paul wrote something to the list a while back about mountain goats and the
dangerous lives they lead... Lives that are so dangerous, that they
shouldn't be allowed to live them. They could... hurt themselves. Telling
lions to quite trying to tackle cape buffalo would also be a good idea.
This could be why they are always rejected for life insurance.>

  In regards to the dangerous lives of mountain goats ... dangerous to
whom? Certainly not the mountain goats, as they tend to do quite well in
the mountains and cliffs; animals tend not to do things which impair their
survival, especially when that activity is daily (the cliff climbing),
save humans [for the most part]. For the most part, the cliff-side capers
are foraging events, less than 1/3 of the time of the day spent up the
steep surfaces of the world. As for cape buffalo and lions, few lions do
this, fewer take on elephants, and NONE do it alone; most of those that
attack the bigger animals tend to be rogue males or the occassional male
"pride" that pops up, meaning the heavier, larger males are tacking the
heavier larger prey. But not commonly ... for there are far more female
lions ensuring the survival of their species by coordinately hunting much
smaller prey than buffalo and elephant. Female lions tend to insure
themselves quite regularly; rather, life is worse for the lion _cubs_ than
it is for either male lions or lionesses on the hunt, as they are common
targets for warthogs, hyenas, other lions, and leopards.

<I guess this goes to show that there are oh so many interpretations once
can make, with no real way of knowing which is correct.>

  Yes. We can make a lot of interpretations based on the possibility of
young and old cooperatively hunting, so far mostly suggested for
*Gorgosaurus* and *Albertosaurus,* and unproven but for 'net and lay
comments in regards to *rex* and *Tarbosaurus.* However, as noted before,
this requires that the young be largely _in the way_ of the chased prey --
when chased prey runs, it _runs_, not walks, and few animals (as an
example) step in front of a running elephant or even bull, as it is as
likely to step on you as gore you. To avoid this, it would be just as
easily to run _alongside_ the prey, but then you are largely aside or
behind it, nipping it in the bud, as it were, and largely eliminate the
need for larger adults to be behind the prey. A screaming pack of small
tyrannosaurs taking on a subadult to adult trike, unable to hit either of
them, and running to keep itself safe (since apparently they didn't herd
based on the absence of a multi-member bonebed of *Triceratops*, it would
be unable to "call" for help) is already on its way into a potential
ambush; at their leisure, the adults can maneuver themselves in the thick
to "intercept" prey. This was largely the scenario forwarded by Currie.
The difficulty in reversing this position -- the reason I called on this
one -- (that of larger chasing prey into smaller's waiting maws) is that
this not only ignores nature's innate selfishness (as lions show, once at
the kill with blood, they start eating, bar none; a cheetah, exhausted
from the hunt, eats before calling her young to the carcass) but that it
makes little use for the young ones to be part of the pack strategy, and I
beleive this led to Currie's suggestion that it was the smaller animals
that did the chasing. Larger birds of prey do get scared and offended by
smaller birds of prey, they do fly away, harangued and harassed; it isn't
hard to see this as a possibility in the fossil record, with roles
slightly altered (the harangued is food for the small). However, Kris'
reversal DOES make use of anoter aspect of nature: exploitation. [More on
this below.]

<And just to mention it... I think that this idea is sometimes lost when
we start discussing theropod hunting strategies. We have the habit of
"Mammalizing" them. Again, I think it was Paul who once said something
along the lines of, "An allosaur who held on to an irrate apatosaur was a
short-lived allosaur." Wild dogs, lions, hyenas, wolves... all like to
wrestle to the ground or hold on to and suffocate their prey... Close
quater combat. They are built for it. Obviously, theropods were an
entirely different ball of wax.>

  They may have had their thing, one way or another. Grouped "hunting"
fish, like piranha or barracuda, tend to behave similarly to mobbing birds
that attempt to take down flying prey: shear numbers of annoying and quite
painful contact, the ol' "hit and run" strategy. I try to use as broad
parallels as I can when discussing applying behaviors to dead things,
because when one looks at the totality, and finds patterns in life for
behavior, we find that more and more animal histories can be more easily
predicted than not. In the mobbing scenario, similar behaviors occur wit
hyenas and cape dogs, suggesting a rather peculiar universality between
land, sea, and air. In this case, tyrannosaurs, one sees how other animals
with similar age-classed or small-group pack, behave: both wolves and
lions lay traps, as an example, but no fish does, and for the most part,
neither does a bird; crocs do, often with groups laying exposed, obvious,
while others sneak, possibly to "divert" attention from the real threat.
When more and more parallels are found, and these correspond to what
fossil finds suggest, it is more likely to be similar way back when as it
is now. If this is "mammalization," it would seem more likely then that
similar to same life habit and hunting behavior is simply more commonly
used among species throughout time: the simpler, the better. Very, very
few animals use very complicated, deception-prone, trail-chasing behaviors
for hunting, among them for the most part only dolphin, wolves, and
humans. Nature has a good thing, so why change it?

<Maybe there wasn't any sort of partitioned hunting strategy. Possibly,
conversations such the following didn't take place within your typical
tyrant family... "Jerry, you and your brothers and sisters wait over there
behind those trees while mommy and I chase dinner to you"... Or... "Jerry,
please try and make sure that your sister and brother steer dinner closure
to your mother and I this time." (Imagine the last one being said by
Archie Bunker.) In stead, maybe, it was a free for all... Lion style
(simply for the sake of how we like to comare big theropods to lions all
the time).>

  Well, as Kris said before, maybe theropods did things a little
differently than we expect. However, the fossil record can be explained in
accordance to this simplified condition, continuing from my use of the
term "exploitation," as used above:

  1. With such a strategy as Currie's, you don't even need adults: the
young can do this on their own, eventually wearing the prey out. Food is
left to the young, who just start to dig in. The adults, smelling the
food, come running, and by then, the young have had enough to keep them
going for a while longer. The adults dig in on the fresh kill, and feast
themselves rotten. This is an exaptation of Horner's idea.

  2. The other strategy is that the juveniles will dig in after the
_adults_ kill the food, as part of a dependant-young strategy, which the
adults seem to have little problem with. This will work if, say, the group
is a pack ... otherwise, if they weren't, as sure as lions are picky about
letting jackals and hyenas and vultures eat from THEIR food, the juveniles
would not eat till the adults gorged themselves. No true cooperation in
either scenario is neccessary.

<Would make sense for you to grow up pretty freakin fast so that you could
push your way to the dinner table now wouldn't it? That is of course, if
your family sat down together for dinner to begin with.>

  Why would that be the imperative when most of your life, over 2/3 of it,
is spent smaller than this apparent optimal size? 2/3 of your life spent
either too big or too small than the most preserved size, 1/3 only spent
at the large, take-on-anything size, and over 1/3 of it in the smallest.
Humans have a similar curve as noted, and for the most part, we humans
tend not to be in a hurry to grow up, and spend most of our life in a
productive, 25-45 year span where we are bth most public, most capable of
breeding, and most capable of dealing with life; oldest and youngest are
not, yet there are more young than old, suggesting care of the young, or
use of the young in a particular, "developed" niche. This is also not
mammalization, but historic.

  The theorized long life of the pre-adult in tyrannosaurs suggests that
sustained care for juvenility was enforced, keeping them young, then
growth-spurting into adolescence, then into adulthood, creating three
age-classes that so far appear to be distinct from one another. This
usually happens, as in humans, with segregated life histories: the young
are sustained young, for either parental care or use as a small animal,
then grow to a condition that is intermediate between the juvenile and
potentially isolated or lone adult. "Sue" may never have had a family, as
the oldest tyrants are rare discoveries, but cooperation may have only
favored the juvenile and subadult. Perhaps the subadults formed the main
clan, surviving and preserving more carcasses because of care from others,
so too would young tend to be protected, rather than the old, left to fend
for themselves or serve a rarer role. All based on preservation, of
course. And isn't it odd that in the smallest phase of your life, that is
the only time you can breed? You have that short period, maybe 5-10 years,
to mate, lay, ensure hatching, and that your young live to a size to feed
for themselves: would this be enough time to grow a pack, group with other
tyrants, and develop a social communal system? More likely an exploitive
system would develope in this short period, or everyone just kinda ...
stuck around.... The separation of ages by growth spurts with prolongated
periods before maximum size and adulthood, likely spent ensuring the
survival of your species in the case of breeding, seems to suggest the
young were very important in the survival of rexes in general, and they
may very well have been communal during this most vulnerable period. I
find it less then odd therefore, that young are ill-preserved: they tend
not to die, meaning they tend not to be involved in the very risky
prospect of being in front of angry, injured, dying prey. Maybe they were
never involved in the hunt after all.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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