Re: T. rex vision

[Flyinggoat@aol.com]

>That the motion of prey is important to predators is >demonstrated by new
born fawns or baby ground birds who sit >motionless if danger lurks. 

   With mammals (at least with ruminants,as far as I know), the newborn
animal is born smelling of blood and amniotic fluid.  After it's mother
cleans it up, which the mother undertakes immediatly, the newborn HAS NO
SCENT (just ask any Disney animal movie.  No, actually this is believed to be
a survival characteristic, and has been recognised in the wild.).  And the
newborn animal has one thing that the baby bird frequently does not.  It has
a protective, camouflage pattern of hair.  Witness the fawn's juvenile
coloring,or the baby wild pig's juvenile coloring.
    These seem to me to be characteristics of an animal that 'freezes' to
avoid detection by sight in order to use the camouflage to best advantage.
Not because whatever hunts it only senses motion.  I beleive this is a
reptile-amphibian trait.
    The baby bird, on the other hand, freezes when hawk shapes pass over it.
This would be dependant on the opening of the bird's eyes to detect this, and
by the time most baby bird's eyes are open, they have SOME kind of plumage,
and again, they freeze to put the camouflage of the plumage into optimal use.
 Before their eyes are open, they usually are that all-over-pink color and
are very much detectable by vision.  (b&w hunters would see a light-colored
outline of a baby bird-shape.  No camouflage.)
   Most higher hunters will recognise the differences in moving objects.  I
know birds have been studied where chicks can tell the difference between
hawks-in-flight and non-hawks-in-flight by shape.  Ken's experience with a
hungry snake shows that snakes do not have this ability. (and this is
applicable to other reptiles.  My brother has  been bitten by turtles and
salamanders in the same situation.  Yes, I know salamanders are amphibians).
 Humans are used to vision that allows us to distinguish between a dead
mouse, and a hand reaching into a cage.  The reptile just sees movements that
are similar and ALL of it's hunting skills are based in this, or heat-sensing
(or in special cases like in rattlesnakes, they sense electrical fields), or
smell. NOT shape identification.
   If BIRDS can tell shapes apart, but REPTILES cannot, DINOSAURS are still
up for grabs on whether or not they could distinguish shapes apart from
motion.  Do dinosaurs share the primitive characteristic of vision in
reptiles, or the more sophisticated vision of birds?  How do we know?

Betty Cunningham(Flyinggoat@aol.com)
(sclerotic rings are present in both birds and reptiles.  No help there)