h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Why has no animal evolved green fur? Green pigmentation abounds in many animal species, but why no green fur?

The Incredible Hulk is the only known animal to have green fur, but it is an anomoly and shouldn't be considered a species of animal. The kid who lives down the block from me has green hair and a pierced tongue. He definitely is an animal.

What do the Incredible Hulk and the kid down the block from me have in common, besides their green hair? They can't attract a woman, and will never have sex. Therefore their green fur will never be passed down to offspring to carry on that trait.

So, green fur is unattractive and serves no useful purpose in the evolutionary scheme of things. Any mutation that results in green hair will quickly die out.

So many predators only have black-and-white vision, that grey or brown are as good as green as far as most prey animals are concerned.

It's easy to see everything from a human perspective, and we do have fairly good colour vision, as I believe is the case for many other primates. If you eat fruit, and want to tell if a particular piece of fruit is ripe without walking or climbing to reach it, distinguishing between red, green, and blue can be very handy.

If you're a creature that only eats green things, the pressure to develop colour vision is much less.
If you're a creature that eats other creatures, smell, movement and noise are quite effective ways of distinguishing plants from animals.

Some birds have green feathers, but this is an 'attraction' thing, like somebody wearing a green shirt or a green dress 'cos it looks good. Animals don't have green fur because a lot of them are colour-blind, or can only see colour poorly. (Birds, for some reason, aren't colour-blind.) Consequently, camouflage only has to cope with light and shade. So black stripes or spots on a orange / brown background are as good as, say, brown on green.