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I'm curious about juvenile sauropod
trackways. Are there many of those preserved in the fossil record?
I'm just a fan, not a pro, but I can't think of any off the top of
my head.
I notice that a lot of large dog breeds
have pups that need to "grow into their paws." Is it possible that
young sauropods would have large feet relative to body size that
spread the pressure of the print too widely to leave a deep
impression? Maybe when they were first large enough to move with a
herd, they were still not stepping with enough force to create
impressions that would survive as fossils.
ÂThanks,
ÂJoe
On 7/2/2019 7:02 PM, John Bois wrote:
Good points. Other possible strategies might have been the
Emperor penguin strategy...one parent goes off to eat, returns
and relieves the other parent...also possible is alternate
year nesting giving time for recuperation of habitat.
Whether sauropods abandoned their nests or guarded them
until hatching, as far as I know there is no evidence either
way. I'm not sure that the lay and leave strategy deserves
default hypothesis, however! The bracket argument _is_
supporting evidence for at least minimal PI...guarding
perhaps. However, others have noted both the malleability of
behavioral traits over evol time _and_ the rarity of reversing
PI once it is established within a clade.
I'm struggling to think of a modern R-strategist that makes
a highly visible and recognisable nest that
doesn't protect it in some way, even if they abandon the
hatchlings soon after birth. Those species that
abandon their eggs as soon as they're laid tend to go to
great pains to hide the nest, making the location
of the eggs as inconspicuous as possible. Somehow I can't
see a sauropod being able to do that. It's not
like they had the luxury of flying to remote predator-free
islands.
Dr Paul makes an excellent point though, about what would
have happened to surrounding vegetation if a
large colony of sauropods remained in one area for any
length of time. Perhaps adult sauropods built up
extra fat before breeding, and fasted while guarding their
nests? Or perhaps only a few sauropods
remained behind to protect the nest colony, while most of
them moved on? Creche behaviour is known in
both ostriches and caimans (albeit towards hatchlings rather
than nests), which is a pretty good extant
phylogenetic bracket for dinosaurs. :-)
--
Dann Pigdon
On Tue, Jul 2nd, 2019 at 11:45 PM, John Bois <mjohn.bois@gmail.com> wrote:
> We don't know how the sauropods managed their
reproductive effort. Strong
> arguments benefit both sides: did they lay and leave,
like sea turtles; or,
> did they at least guard their nests like gators?
> I think that if you come from stock who apply parental
advantage to their
> offspring, and that your offspring are delectable to
many predators, that
> you also would want to intervene in that direction.
Certainly, your qualms
> are valid. Just as a thought experiment, let us say
that they _did_ guard
> their nests, how could they do that without either
starving or destroying
> the surrounding habitat.
> Penguin model: send off your parental partner to feed
while you guard. When
> your partner returns, you go off and your significant
other guards your
> babies.
> Emu model: store energy and water and go into extended,
low-energy mode.
> Don't eat for weeks at a time. Pee crystalized uric
acid to conserve your
> water!
> Cicada model: don't reproduce every year. This will
give the producers time
> to recover and trick your predators.
> The problem for you as a sauropod, is that your eggs
represent a
> concentrated resource to your predators. If you are
colonial (check), you
> return to the same nest sites (check), and you cannot
hide or lay remotely
> (check, check), you are in a bind. When your babies
hatch, they can
> disburse, hide, etc. and enjoy some relative security.
> Re predation on adults: I agree with Dr. Habib on this.
Perhaps ostriches
> are a good model...predation on adults is rare,
predation on eggs and
> chicks is excessive. Suffice it to say that the
majority of an organisms
> life is spent in adulthood. This then is the period
where defense against
> predators should be strongest. Speed for ostriches, a
mean kick for zebras,
> communal defense for water buffalo (e.g., Battle at
Serengeti), stealth for
> squirrels, whatever it is, no doubt sauropods were
likely able to defend
> themselves (with exceptions of course).
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