RE: Camouflage

["Cunningham, Betty" <Cunningham@sega.com>]

Steve Jackson writes:
> We can't assume that, just because modern crocs are not well
>"camouflaged" from above, that Cretaceous ones did not possess such
>coloration.

and Rob wrote:
>>All this depends on how you define "camouflage."  The grey/green color,
>>common in crocodilians, would blend in to the river/marsh bottom
>>rather well.

let me use some examples about how animals in water are NOT camouflaged   
when viewed from enough height.
 Flounders live on the bottom.  Their camouflage is to hide against the   
"bottom" from anything that can also precieve visually the "bottom"  From   
a height above the water they are virtually indistinguishable from the   
bottom because the conditions of atmosphere and depth are affecting   
equally the viewer's preception of the "bottom" and the camouflage of the   
flounder.  It works.
 The grey whale lives in the ocean in a variety of depths but is required   
to spend much time at or near the surface.  The whale is camouflaged so   
as to have less visual perception when viewed from the side at some   
distance; so that viewers approaching the animal may not precieve the   
animal immediatly (if the grey whale was boldly marked like an orca it   
would be spotted much earlier).  The camouflage is so as to blend in with   
the way the water itself is precieved by the viewer AT THAT ANGLE. When   
viewed from above or below, the lighting no longer works with the   
camouflage, but against it. You go on a whale-spotting plane ride and you   
can percieve whales at huge distances because the transparency and depth   
of the water is precieved differently from above than the whale is.  The   
camouflage is not functional at different angles because vertebrate   
animals cannot mimick the visual properties of a transparency.  Think of   
submarine spotters as another example of spotting things in water from a   
height.
 Crocodiles that would feed on dinosaurs, if camouflaged like modern   
crocodiles would need to have similar strategems as modern crocs, which   
means they would be camouflaged when percieved from short- low height   
distances (drinking height) so as to appear to be part of the natural   
environment such as a log, if they don't simply remain unspotted by   
simply not moving.  The simply not-moving strategem is remarkably   
affective, even with animals as depth-perceptive as humans are.  (I am   
not trained in the study of the comparible anatomy of vision, but am   
trained in the human-biased "visual arts")  Try watching the last 5   
minutes of the movie "Harry and the Hendersons" and ask yourself where   
the other bigfoots were.
 If there was an animal that hunted crocs, It would certainly be an   
advantage to view crocs from a height of 30 feet. Even a non-moving croc   
can be spotted by something that is actively looking for it if given   
enough time to look.  Even if this animal had different visual   
accuity/preception than humans, it would still be affected by much of the   
same physics that affect the way light and atmosphere effect the   
perceived environment.
   I'm not saying somebody like T rex DID hunt Cretaceous crocs, but they   
could have spotted them better if they were looking for them than someone   
with a height of only 5' 6".
 If a sauropod was watching for crocs, they'd probably spot them right   
off, (if we assume the eyeball structure of a T rex and a sauropod to be   
similar enough) but would still need to eventually approach the water to   
drink.
 Who knows of crocs ate sauropods?

 -Betty
Betty.Cunningham@sega.com