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Re: sauropod breeding



Fascinating,

I remember seeing reconstructions of Jurassic ecosystems in
europe. They showed very small numbers of predators and
seemed to indicate that the sauropod populations were
controlled by other factors than predation.
Of course trackway patterns with young in the middle
(assuming they weren't always running off) suggests
predation on young adults was a major threat.

Still, it is interesting to consider the possibility that if
Carnosaurs were indeed not able to control the population
then it would seem to follow that the juvenile stages would
have to be not controlled through predation (this does not
preclude predators eating 99% of young, if you assume that
the last 1% can supply the adult population).

So, in other words whatever Sauropods were doing to
reproduce, they were doing it well enough not to have their
population effected noticably by predation.

One more possibility regarding parental care (for fun):
It is theoretically possible that the first years could be
spent in a nest.

It would not take long for an adult in most of these species
to move a dozen or so trees (small ones or branches anyway).

The mass/surface area ration would seem to allow the
guarding of a communal nest by a couple of adults for a fair
period of time before they got too hungry (the rest of the
herd would be somewhere else).

-Jonas Weselake-George
Ottawa Paleontological Society


----- Original Message -----
From: Allan Edels <edels@msn.com>
To: <paleo@ncf.ca>; <dinosaur@usc.edu>
Sent: Monday, March 13, 2006 2:42 PM
Subject: Re: sauropod breeding


Consider the trackway evidence which seems to show that
small sauropods
travelled with adults and sub-adults surrounding them.  This
does NOT apply
to sauropods under a certain age or size [say, less than 7
feet (~2.1 m)
long, or less then 4 years old. (Note that I do not have
references for
these numbers)].  These young and small sauropods are not
represented in
trackways that we've found.

This may be preservational bias (i.e. the young ones were
too small to leave
a deep enough track, and those that they did leave, were
obliterated by the
passage of the large ones) or maybe the young did not travel
until they
reached the cut-over size/age.  (They may have lived in
isolated, somewhat
protected areas until the next swing of the herd's
migration - and then
moved when they were old or large enough).

So the intermediary size young adult (and sub-adult)
travelled with the
herd(s).  Based on other estimates of growth that I've
heard/read, three
years should be enough time to allow the young saropods to
grow to a size
acceptable to travelling with the herd.

BTW, I think that sauropods (in general, of course) nested
each year.  This
would give us the interesting scenario of the 3 year olds
(as they wait for
the return of the herd) protecting the much younger ones.
Possibly, in lieu
of parental care, we have sibling care [or some other such
similar
altruistic arrangement - cousin care, pseudo-sibling care,
etc].

One more thing - It is highly likely, in the scenarios we've
been
describing, that recently matured young males would leave
the herd for a
different herd (possibly going solo for a while) to prevent
genetic problems
(Of course, they wouldn't think of the reason that way... Or
would
they........
:-)).

Hope this helps (or at least stirs someone's thinking),

Allan Edels


>From: paleo@ncf.ca
>Reply-To: paleo@ncf.ca
>To: dinosaur@usc.edu
>Subject: Re: sauropod breeding
>Date: Sun, 12 Mar 2006 18:16:09 -0500
>
>So, We probably have a situation where juveniles could
>survive without having to resort to adults carrying them
>around, lifting them into trees, or little tiny fangs.
>
>My questions are:
>What would the intermediate young adult look like?
>It couldn't hide, but could it's relatively small size
allow
>it to defend itself more easily (rearing on it's hind legs
>and ramming)?
>
>Would it eventually link up with other sauropods for
>protection?
>If so, would non-blood relatives be willing to take it in
>(are new genes worth adopting non-relatives)?
>Would this lead to different group compositions (ie.
>non-affiliated males "rutting groups" as separate from
>female herds?)
>
>Would the need for relatives to pass through a local area
to
>pick up the juveniles of a few years ago effect migration
>patterns and how would relatively regional populations
>effect a predators ability to track that population (I am
>thinking mara masai here).
>Is this consistent with the highly mobile Carnosaur
>juveniles?
>
>Is there any way to test these possibilities?
>
>-Jonas Weselake-George
>Ottawa Paleontological Society
>
>
>----- Original Message -----
>From: David Marjanovic <david.marjanovic@gmx.at>
>To: DML <dinosaur@usc.edu>
>Sent: Sunday, March 12, 2006 5:54 PM
>Subject: Re: sauropod breeding
>
>
> > Well, you can probably assume highly cryptic colouring
and
>a deeply
> > skittish nature,
>
>A skittish nature at the same time as an inability to run?
>Is that of much
>use? :-/
>
> > but consider sea turtles --
>
>Yes, but they are armored and can swim at reasonable
speeds.
>
> > Also note that the whip-tail sauropods and mace-tail
>sauropods probably
> > have these defensive measures from a small size, and
that
>they'd apply
> > to equivalently sized predators just fine.  So
>Ornithosteles is fine
> > with the hatchlings, and maybe even the yearlings, but
has
>some serious
> > cost-benefit concerns thereafter.
>
>Imaginable, but that's where, say, juvenile carnosaurs may
>start...
>
>
>