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anti-social Tyrannosaurs



First may I explain my background briefly. I am 39, not in paleontology, and
have been auditing this list for 2 months. I am currently changing careers
from management to computer programming and love this list. I have read
10-15 books on dinosaurs and
have never had an adult conversation about dinos with anyone who had any
real knowledge about them. So thanks to all who have been an oasis for this
interest of mine with their ideas and discussions in a public format. I had
been dependent on CNN and USA Today for any new info and this list has cost
me valuable study time,
but I look forward to scanning the posts and need my nightly dino-fix
nightly now.
   I believe tyrannosaurs may have lived in mixed social groups and that
they probably exercised several social strategies during their long tenure
on earth. The environmental pressures that drive both evolution and behavior
would probably have shifted the best survival strategies  during the
millions of years of their existence.
The best  times tend to promote more social ties and ecological stresses
usually break down or reduce social bonds.
   With the following premises (for you DR. Holtz)  I will try to elaborate
more. Again my apologies if this is too non-professional. I have given this
some thought over the last few years though. I'll try to avoid the basal
premises.
   1. Large herds of herbivores probably gathered, if not year round, then
for mating/birthing or migratory purposes. The herds would have devastated
the local resources of plant life rapidly, even assuming the vegetation
regenerated rapidly. Is there any modern plants which could regenerate
rapidly enough to support the tonnage estimated in these herds(botanists
insert help here please).So these herds would have
been forced to have a mobile feeding strategy that was affected by many
factors such as location and abundance of other herbivores using the same
food sources, ability to travel effectively, and many others. The balance
between available food and consumers will always regulate the maximum number
of herbivores and their sizes and species viability,such as gene pool,
ability to reach breeding age, and the environments to raise young
efficiently(it is useless to live in an area which provides abundant food
and water if your young cannot survive predation or climatic pressures).
Given the  probable migration of these herds, then at least some of the
predators probably also followed them. But which ones? The  tyrannosaurs
were one of if not the top predator in the late cretaceous. Would that
affect whether or not they migrated? Because I believed they scavenged first
and hunted second (why risk injury needlessly)
the lower food available might have forced some to follow the herds, but not
all. I do not think all herbivores migrated, only those which could not
effectively compete in an ecosystem of lowered resources, or herbivores who
migrated for other reasons like climate and reproduction. So it seems likely
to me that along with resident herbivores
there would be predators or at least scavengers.
   So which predators may have followed the herds? I believe, like most
things, the answer is not binary(either migratory or non-migratory) but a
combination. The most logical scenario to me is this. The regional herbivore
population is very dynamic, depending on the plant life available. As the
region becomes depleted of food, the least proficient species at finding
nutrition in this more competitive ecosystem move on. The hardier (or
non-migratory for other reasons) herbivores remain. The predators undergo
similar adaptations to the ecosystem. The predators most likely to remain
would be those who competed effectively in these leaner times. The top
scavenger/predator would have varied strategies because it was the top
scav/pred
and could dictate regional strategies for lesser carnivores. If the lean
times could support part but not all of the top predators (assuming
tyrannosaur for this discussion)
of a population, then within a genus or species, which animals migrated and
which remained?
   The problem of what did a baby tyrannosaur need to develop is now
important. Did the infant(my preference to chick) have inborn abilities to
survive or did it need to be
taught? Obviously the 65 million year question, which cannot be answered
directly but might someday be inferred from other data such as nesting and
parental care findings.
The other part of this question that I can't ignore is that live birth and
parenting practices may have been driven by the size of the newborn head and
the amount of information that can be stored. A solution to the real
conflict between size of the birth canal and newborn head size came with
parental care. The infant does not need to be born with as much instinctual
information because by extending the time the infant spends with their
parents as mentors the young can add these teachings to their knowledge.
This is also a more effective way as the young learn successful strategies
in their current environment from successfully reproducing adults. If, as a
predator, a tyrannosaur utilized the impressive sensory potential found in
fossils and also had
some other behavioral complexities in social structures or mating , perhaps
the tyrannosaur found the same strategy, probably in smaller eggs(I'm
suspicious of dino live births). The parenting strategy vs.. lay em and
leave em seems more probable for a top predator who has greater control of
their environment than for a secondary predator. If this were true of
tyrannosaurs, possibly the order within favored reproductive age females. As
resources diminished the males, perhaps in hunting packs, followed the herds
of herbivores. The tyrannosaur youth which were dependent
upon adult care and the mothers remained and survived on the reduced food
supply. The females probably would be with their families in territories
fiercely defended to ensure adequate resources in lean times. These
territories may have existed for the life of the adult female if resources
supported them. The new breeding age females would establish new territories
or possibly oust another female for a prime location.
The families might share food or they might have fights near territorial
borders and there might be relatives which had bordering territory which got
special trespassing rights. If resources were critical, I imagine the
sibling youth had mortal competition for food and even the mothers may have
chosen which young to raise and which to ignore.
The acute sensory abilities the fossils suggest make me think that most
tyrannosaurs knew when there was food available in a neighboring territory.
The hunger pressures and parental concerns must have lead to some hellacious
fights over carcasses. As is
evidenced repeatedly, extreme desperation leads to extreme measures. Imagine
that there were some bouts for the ages in those settings.
    So the males may have followed the herds of herbivores when times were
lean and maybe the females stayed behind with the less mobile young. This
would make me think the females would be larger and more able to withstand a
fight with another tyrannosaur. Protect it's kill or territory, defend it's
young, or survive a lean time with greater fat reserves all support a need
for larger size. The male strategies genetically
might have favored a more streamlined walker who could follow prey over
great distances and perhaps even scavenge over a wider range if he were
better suited to walking than females. The need to defend(territories and
young)diminished, the more effective a more mobile form becomes. So from my
views, amateur be they may, this is how I see dimorphism and social
strategies within tyrannosaurs.
   Please feel free to correct my mistakes in concepts. But if you must play
teacher and want to correct grammatical mistakes, spelling, or other
"labels" that don't affect understanding the concepts, please reply off list
so the others aren't indulged by things
that don't further anyones interest in dinosaurs.

Troodon
                     troodon1@worldnet.att.net
   If we only believe in the facts we can touch, then Newton, Einstein,
Darwin,Sagan, and Dr. King were only dreamers and not visionaries. We often
need visions by great people so we will know what we are looking for as well
as why.