Where's the Green?

"O Paddy dear, and did you hear the news that's goin' round?
The Shamrock is by law forbid to grow on Irish ground!

No more St. Patrick's Day we'll keep, his color can't be seen,

For there's a cruel new law against the Wearin' of the Green"

The day before yesterday was, of course, St. Patrick's Day, when everyone pretends to be Irish.   Like many people, I spent part of the evening at a bar, where I engaged in one of my favorite past-times, people watching.  One of the first things I noticed was that a lot of people were wearing green.  It was then that something kind of odd dawned on me.

There really aren't many green animals.

This isn't going to be a profound question with a profound answer.  I just realized that there aren't many green animals.  Which is odd, if you think about it - plants tend to be green, and animals tend to spend a lot of time among plants, so you think there would be a lot of green camouflage out there.

As near as I can tell, there are no green mammals... I mean, bright green (or, to be fair, blue or purple).  You've got a few that have kind of an olive hue, but no green.  The closest I can think of would be sloths, and that's not even a birth-color; sloth hairs, in the wild, anyway, tend to turn green with algae, providing camouflage in the tree-tops.  A great adaptation, but how have none of the other rainforest mammals - monkeys, anteaters, squirrels - evolved green fur?

There are some green birds, but in a way that makes less sense than no green mammals.  Birds, with their ability to fly away from danger, tend to be a lot more garish than mammals, since they don't need to hide as well.

Reptiles and amphibians are the ones that surprise me the most.  Ask someone - not looking at a picture - what color a crocodile is, and they'll say green.  No - they're really grey or brown, and alligators tend to be a bluish-black.  Same about snakes - green.  Of the dozen odd species of snake found in my area, I can only think of one which is actually green.  The others are black, brown, orange, or some combination thereof.

"It's not easy being green... so I decided not to even bother."

Maybe there is some disadvantage to being green that I don't recognize.  Maybe a green animal would be well camouflaged in the trees, but would stand out too much if it were on the ground.  Certainly in the northern hemisphere it makes sense, since leaves fall off trees for much of the year.  Maybe it's just that some species don't have the genes present for green coloration, and that if such a mutation ever did occur, they'd all have it.

I don't know.  I really have no idea.  What I do know is that it's very hard to work around animals and not feel your head fill with a lot of questions "Why?", "How come?", "What If?"  You can spend a lifetime around animals and still not know more than the basic facts about them.  There are certain things we will probably never know for sure.  Trying to find out is where the fun lies.