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RE: a little background



Some things to consider:

1)      The zippy little things (herbivores), had zippy little predators hunting
for them. (Or trying to catch them).  Some of the zippy little predators
(_Compsognathus_, _Mussaurus_, Troodontids, _Archaeopteryx_, etc.) never
grew to the scale that the mega-sized theropods did.

2)      It appears that herbivores usually had large litters. (i.e. multiple
numbers of eggs per nest - e.g. 10, 12, 16, 18, 22, 24, or 30 eggs).

3)      Likewise, some theropod nests appear to have had 2 eggs usually (with
some apparently laying as many as 8 eggs [possibly Therizinosaurs]).

4)      Because of this, and other factors, the predator/prey ratio was 3-7 per
100 (or lower).  This SEEMS to be reflected in the fossil record
(preservational bias?).

5)      The larger herbivores appear to have traveled in large herds (Jack 
Horner
has often claimed  that the _Maiasaura_ nesting grounds had over 15,000
individuals buried by a massive mudslide - and the animals came back the
next year[?] to make new nests).  This tactic DOES protect the majority of
the herd.

6)      Not all of the apparent prey animals were available to be eaten by the
predators, and not all of them were DESIRED by the predator.  (For instance,
who here really wants to eat Horseshoe Crab?  I know where you can find
millions of them).  Animals also have things that they like to eat and other
things that they don't.

7)      If we focus on the Late Maastrictian, we have mostly _T. rex_ and
_Triceratops_ dominating the Western American continent.  While there are
other dinosaurs around (most notably hadrosaurs, and there were also some
smaller sauropods), these 2 dinos were the majority of the megafauna for
nearly the last 500,000 years of the Cretaceous.

What do I mean by all this?

The likely situation is that prey vastly outnumbered prey, much like most
environments today.  The predators, possessing superior weapons and speed,
are STILL usually outnumbered by the prey.  The prey animals continue to
multiply and survive (at least most of them).  [There is currently only one
known super-predator - MAN, who seems to be able to remove prey entirely
from an environment].

The mega-predators would eat the other mega-fauna, as available.  They would
also eat any of the smaller prey when they could.  (People eat rabbit,
pigeons, small trout - not just cattle, sheep, etc.)

Hope this is clear enough (It's nearly 5:00 AM here!).

Allan Edels


-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Graydon
Sent: Saturday, March 09, 2002 10:26 PM
To: John R Hutchinson
Cc: dinosaur-usc.edu
Subject: Re: a little background


On Thu, Feb 28, 2002 at 12:39:07PM -0800, John R Hutchinson sent:
> Now we're caught up.  I hope people understand that this was not some
> project that Mariano and I sketched on a napkin after a few beers last
> week, and decided to publish as an assault on paleontology, and then
> abandon to let paleontologists pick up the pieces.  This was a lot of
> work and we are serious about it, and I will continue pursuing these
> sorts of scientific questions for the rest of my career.  I welcome
> disagreement with our work as long as it is scientific and not
> superficial.  I expect SVP next year will have at least one talk
> criticizing our research, and I'm sorry that I won't be there this
> year (first time in 6 yrs!) to respond.  We'll work things out in the
> scientific peer review process over the next few years, I hope.

I think it's extremely interesting.

(My own suspicion is that the theropod mass models are badly out of
whack; I will cheerfully believe in large theropods with half their body
mass in their legs, and have the suspicion that the apparent general
size limit for that body plan may be at a much lower mass point that
hitherto suspected.)


I'm also thinking that it does something kinda violent to models of
dinosaurian ecology.

We have little zippy dinos -- everyone agrees that, proportionately,
hypsilodonts and ornithomimids, etc. had the ability for a true run --
and we have big, slow dinos; multi-ton carnivores and multi-ton
herbivores.

The multi-ton herbivores ecologically dominate; really inexplicably high
proportions of the ecology.

Why?

The little zippy guys aren't at risk of predation, so long as they can
outrun a predator which can't profitably consume them on an
effort/return basis, and which can't reliably catch them, either.

Which implies that either the juvenile theropods were just as fast, and
keeping the numbers of the little zippy guys down -- which sugguests a
horridly unstable ecology, as per the arctic lemming cycle -- or, well,
what?  The striding giant predators can consume the equally locomotively
constrained giant herbivores, sure, and the herbivores want to be big if
they're already slow, but if so, why are the smaller dinos so rare and
the large ones so common?

--
graydon@dsl.ca   |  Hige sceal þe heardra, heorte þe cenre,
                 |  mod sceal þe mare þe ure maegen lytlað.
                 |   -- Beorhtwold, "The Battle of Maldon"