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Re: attack on dinosaur--horrific video




----- Original Message ----- From: "Andreas Johansson" <andreasj@gmail.com>
To: <dinosaur@usc.edu>
Sent: Thursday, November 22, 2007 9:32 AM
Subject: Re: attack on dinosaur--horrific video



Well, it should lead us to the conclusion that nest predation can't be
all that bad even for night-blind species: else ostriches would have
been exinct long ago.

_All_ continental ground nesting birds depend on concealment not defence--the nests are indefensible at night. Darwin talks about having to practically ride _over_ Rhea nests before discovering them. Bertram talks about the total invisibility of ostrich nests beyond ten metres distance. The question for mesozoic comparison is: could large dinosaurs lacking the cover of prairie and savannah grasses, hide? Surely, they could in forested areas--but then they would have to deal with the attendant greater diversity and numbers of critters that live there. One of the secrets of ostrich success is great concealment and low predator density of arid grasslands.