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RE: good mothers/the fate of hadrosaurs (fwd)



Date: Sun, 5 Jan 2003 04:44:27 -0500 (EST)
From: Mark Stephen Caponigro <msc39@columbia.edu>
Reply-To: vrtpaleo@usc.edu
To: vrtpaleo@usc.edu
Subject: Re: good mothers/the fate of hadrosaurs

> It had occurred to me that the nesting
> conditions of many penguins might be a possible model for those of
> hadrosaurs, at least those a la Maiasaura.  Skuas might scale-wise more
> closely resemble the predators a community of Maiasaura had to face than
> the leopard that lit into those poor South African penguins.

For adult predation on adults, yes.  I only meant the predation by the
leopard on the penguin colony to represent adult predation on offspring.
But I agree that scaling and specific predatory threat are everything in
this.  By the way, some bird species are capable of switching strategies:
from colonial/defensive to solitary/concealment depending on the specific
predator!  But I would love to see a hadrosaur trying to hide.

> That is, from what data we have,
> it is quite likely that small-scale predators such as Troodon were able to
> make off with a considerable proportion of Maiasaura nestlings.  But it is
> not at all clear how that population of Maiasaura, fixed in that location
> for a goodly period of time, survived at all, if it is taken as dogma that
> all adult hadrosaurs could do nothing to defend themselves from adult
> tyrannosurs.

Right.  They had to defend themselves!
A couple of additional thoughts:  In bird studies, it is notoriously
difficult to attribute predatory blame on a specific nest robber.  They
don't leave their calling card!  Troodon may have been one of a larger
guild who counted hadrosaur offspring as part of their diet.  Interesting to
wonder why only they left evidence. Also, large eye sockets suggest that
Troodon may have been able to see relatively well at night.  If so, I see
this as a rather hellish time for hadrosaurs!  Imagine, you can hardly move
for fear of crushing your children (they very likely had inhibitory
behaviors along these lines); and now comes a predator who can forage during
these dim hours!  Ostrich defense is informative here: their nests are
relatively secure in the day time...at night animals which they didn't fear
at midday drive them off their nest (black-backed jackal, for
instance)!  As a result, ostriches must depend upon concealmenta s their
prime strategy.