On Thu, 8 Apr 2004 16:11:49 +0000 (UTC), spam_bait101{at}yahoo.com (sb)
wrote:

>spam_bait101{at}yahoo.com (sb) wrote in message
news:...
>> How come mammals that live in green forests aren't green (for camouflage) ?
>
>Here's my own take on this:
>
>1. The hypothesis that mammals simply did not manage to find a recipe
>for green pigmentation is not a plausible one: some mammals have green
>eyes, birds and reptiles are often green, and reptiles are earlier on
>the evolutionary tree than mammals. Pigmentation just does not strike
>me as something difficult to find a genetic recipe for (And by the
>way, polar bears turn green in worm zoos because of parasites - if
>they "wanted" to be green, they could at least use this kind of
>symbiosis)
>


There is a difference between pigment color and structural color.
Green and blue in animals is almost always a structural color,
produced by either interference or scattering of light, not by a
pigment that absorbs light.  Also, there is a difference between color
of hair and color of skin.  Mammals can produce structural colors in
their skin.  Reptiles, amphibians, fish, and many invertebrates
produce both pigment and structural colors in cutaneous chromatophore
cells.  Mammalian hair seems to use only melanin as a pigment and
seems unable to produce structural colors of any intensity. (White
hairs do sometimes take on slight hues).

See my literature citation to primate colors in another post in this
thread.
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