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Re: attack on dinosaur--horrific video




----- Original Message ----- From: "Glen Ledingham" <glenled@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, November 21, 2007 4:44 PM
Subject: Re: attack on dinosaur--horrific video



There are a number of observed behaviors that might
have helped dinosaurs avoid egg/nestling predation.
Alligators build self-heating nests and guard them
until the eggs hatch.  After that, they guard their
young.

Yes...and they can also see very well at night, and thus are able (and do) guard against nocturnal predators. This is questionable for non-avian dinosaurs--I have only heard this ability argued for Troodon.


Horner observed that a hypsilophodont rookery
was on an island.

But still, relative to birds who are selected for small size (no doubt partly for concealment) or for long distance migration (for--among other things--nesting remotely), non-avians could neither hide themselves, nor distance themselves from those who would eat their young!


Even if one dino of a breeding pair
had to sit the nest, a mate could help protect it.
These behaviors could probably evolve quickly under
the selective pressure of nest predation.

With respect...the idea that all predatory/competitive strategies can be responded to by selection of adaptive traits must be false--otherwise all species would still be with us (unless we maintain that _all_ extinction is due to physical/climatic changes!). Indeed, the distribution of extant egg layers argues for an almost tyrannical control of their species' distribution by predators.


I saw a video of small birds that had apparently
recently developed the behavior of attacking larger
nesting birds, so it's not just mammals.

Birds, mammals, lizards, snakes--yes, yes. It's additive -e.g., ostriches suffer from all clades.


As I recall, the sclerotic ring served as a night
vision device, and some dinos had large eyes for
preying on night-active critters like mammals.

Birds--and probably non-avian dinosaurs--are/were limited re night vision by their eye structure--sclerotic rings restrict light gathering--owls, for example, must have huge eyes to enhance night vision--crocs lack sclerotic rings, as do we.