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Re: How Did Hadrosaurs Survive? (Was: Hadrosaur "mummy" questions)



on 11/1/02 2:18 PM, Dann Pigdon at dannj@alphalink.com.au wrote:


>> But who taught them? All modern pack animals teach their young how to hunt
>> in a pack. 
> 
> Tyrannosaurs aren't modern animals.

Obviously. But they appear to have more in common with modern birds and
mammals than crocodilians. So they can be compared to those animals, we know
of no reptiles that hunt in packs. If you are going to postulate that rex
was a pack hunter, it pays to look at modern pack hunters, since we are
unable to look at extinct ones.
 
>> The main point is that why would you take a juvinile animal, who
>> will no doubt screw up the hunt and risk loosing a meal and possibly starve.
> 
> Young juveniles (say, a year old) could have concealed themselves and
> watched, or been used to scare up prey to determine which ones were
> easiest to hunt. Animals that are several years old, but not full
> adults, could have guided them, since they probably had several years
> experience themselves.

And where do these young juveniles, just a year old, learn which animals
will make good prey? Which animals are weak, sick or old? Which animals are
submissive and will sacrifice themselves for the good of the herd? These are
skills that are learned over YEARS of active hunting. Even young modern
animals that have been allowed to join the hunt are still guided and taught
by the older, more experienced animals. They do not suddenly spring forth
with everything they need to know after just a season of watching adults. I
seriously doubt that animals just several years old would have the
experience to teach to what amounts to a baby how to take on such a huge
responsibility. To have the entire pack depend on the young ones for
sustenance makes absolutely no sense. Pack hunters also do not just 'scare
up' prey to determine which ones could be readily killed; by the time they
make a run at a herd, they have already picked out an animal and are testing
their assumption. If their assumption is wrong, they fall back and regroup
to try again. 


>> The juviniles needed to be taught by the most experiance hunters in the pack
>> and I don't think sub adults fit this bill.
> 
> You are assuming that the adult tyrannosaurs appeared fully formed (ie.
> special creation) and then started breeding. In that case, there would
> be no-one to teach the young juveniles.

No need to be insulting;) Actually, you're the one who is assuming here.
Let's try this: A male (or female) grows to adulthood and leaves it's pack
to start it's own family. It meets up with a mate and they produce young. If
the adults are incapable of the 'flushing the prey' behavior, who teaches
the babies? And how do the adults eat until the babies are old enough to
participate in hunting? How do the adults even feed their babies in this
case?

> In reality, tyrannosaurs probably had several generations hanging around
> at any one time. Hence young juveniles learn from sub-adults (that is,
> animals large enough to hunt, but still small enough for sustained
> running and manouverability). As the sub-adults grow to full adulthood,
> the juveniles that watched them take over the active role, and they
> adopt the ambush role that their parents before them had (and that they
> had watched). Therefore, full adults teach sub-adults how to ambush,
> sub-adults teach juveniles how to hunt, juveniles grow into hunting
> sub-adults, and sub-adults grow into ambushing adults.

I doubt it. They were too big. In modern and fossil predators the ones who
hunt in packs (and the ones we think hunted in packs ie: Allosaurus) do this
to hunt prey larger than themselves. T.rex was as big as most of the food
items it hunted. What would the advantage be in having such an extended
family together? Why would you need anything more than a small family pack?
You're also assuming that they would produce young every year, so there
would be an endless supply of juveniles to scatter prey animals. What
happens if there's a bad year and the babies die? Who feeds the adults then,
and who would the babies learn from if there were no sub-adults around? What
if there's a small litter or clutch or whatever you want to call it and the
single surviving juvenile is killed or injured during hunting? Hunting is
dangerous. What about disease? Young animals tend to be more vulnerable to
disease than adults, what happens when disease sweeps through the pack and
kills the young ones? Do the adults just roll over and die of starvation? I
just don't buy it. It's a huge risk and makes the forming of new packs or
family groups totally unlikely, for the adults to depend so heavily on the
juveniles for hunting success. In that scenario 'd have to assume that rex
was mainly a scavenger (which I totally disagree with,) and the juveniles
were used for hunting only when the adults were unable to find a carcass or
steal one from another predator.


> I beleive that's what some singing anthropormorphised animals refer to
> as "the circle of life".

No, that's called special rules for T. rex, who was evidently so intelligent
and such a good hunter that it was successful despite the welfare of the
entire group being placed on the shoulders of the young'uns.

Best,

Brett
www.demonpuppy.com