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Re: Big = Old = Advanced?




On Mon, 1 Sep 1997, Ronald Orenstein wrote:
> Most birds, by the way, can
> replace an entire clutch if the first is destroyed.

This contingency must also be considered for non-avian dinosaurs.  And it
also must be considered as an expense in figuring optimal clutch size.

> I think Horner's comment overlooks crypticity.  Turtles, of course, bury
> their eggs, and many hatchling birds (and eggs) are cryptically-coloured
> and can be extremely difficult to spot.  Of course larger animals have more
> trouble with this - but many deer habitually leave their fawns untended for
> long periods, while the fawns "lie up" concealed in vegetation and relying,
> probably, to some degree on their spotted coats to make them harder to
> spot.  It would not surprise me if young dinosaurs, or some species at
> least, may have also had patterns of spots or stripes that aided in their
> concealment (as, say, ostrich chicks do today).

Yes to spots and stripes.  Horner was referring to hatchlings which had
been totally abandoned.  For the deer model to be analagous the dinosaur
mother would have to tend the nest inside deep cover.  This strategy is
only as effective as the stealthiness of the dinosaur.  Dinosaurs tended
to be less secretive inasmuch as they tended to be big--big things are
relatively easier to see.  Perhaps the deer is reaching the upper limit of
this strategy.  Yet, forest elephants exist and are quite hard to spot
(apparently).  However, their rearing strategy doesn't involve crypticity
as far as I know.  Maybe dinosaurs could let the hatchlings scurry into
brush for hiding and then call them into the open for feeding.  Does this
work for any creature today?  It would also seem to advertize the presence
of their hatchlings.  

Also, hatchlings are smaller relative to the parent than a fawn is to a
deer.  Despite probable rapid growth I think this means a longer period in
vulnerable stage.

One more thing.  A deer can carry this strategy better than a dinosaur on
account of nursing.  It may eat high quality forage and convert this
energy to milk, lie quietly while the fawn suckles, and tip toe away.
The dinosaur either would bring undigested matter or regurgitate its
hatchling's meal.  The retching hadrosaurs (a good name for a band) might
give the game away.  I know, she could do that quietly, too (I couldn't
resist the image, though).