Re: T. rex vision

[rowe@lepomis.psych.upenn.edu (Mickey Rowe)]

On yet another can of moving worms...

Betty Cunningham (Flyinggoat@aol.com) attempts to reinforce Ken's
position about visual systems and motion by claiming that snakes and
turtles cannot visually detect stationary objects.  That is absolutely
not universally true.  Certainly you must know about African
egg-eating snakes, right?  Eggs aren't known for their motive
abilities, but snakes most certainly eat them.  Secondly, a lot of
turtles/tortoises/sliders etc. are largely vegetarian.  Plants also
aren't known for their ability to draw attention by moving around.
Betty also attempts to smear salamanders via her brothers experiences.
I've trained most of my animals to take food from my hand (I like to
be 100% certain they're all eating), but I've seen tiger salamanders,
three different species of newt, and (to rescue the reputation of the
poor frog that started this out) two different species of clawed frog
eat freeze dried tubifex, another food not high on the wiggling scale,
with no help from me.  I also rarely feed my turtles their
commercially prepared food sticks by hand because I worry about the
turtles' aim.  They have no trouble finding non-moving objects, and
their directed movements are indicative of visually guided behavior.

Be VERY careful before making statements such as:

>   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?

Neither "reptiles" (no matter how defined) nor birds are a homogeneous
group with regards their abilities to see objects under various
conditions.

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)