If you think about it, green is a pretty damn good colour to be if you are an animal. Whether you are prey or predator, being green will let you hide perfectly amongst lush green undergrowth – letting you pounce out at your unsuspecting prey, or effortlessly evade a predator. Despite this, there are no animals with green fur! You would have thought that one would have evolved some green pigment to help them survive, but they haven’t, and I’ll try and explain why here.
Despite green being everywhere, there is only really one molecule which is green, and that is chlorophyll. Green is everywhere because plants produce it, but in reality, it is very rare, and this is because the colour green is very difficult to create naturally.
Even frogs are not actually green. Frogs are actually a complicated structure of blue and yellow cells. They contain special cells which contain purine crystals, which reflect blue light. Above these crystal containing cells are cells which contain a yellow pigment. As the blue light reflects through the yellow pigments all colours are filtered out except green.
This rather complex arrangements of specialised cells is how most fish and other amphibians look green, and this goes to show just how difficult and unusual it is for nature to produce a green pigment.
Humans and other primates are quite unique in their ability to differentiate between green and red. Most mammals and other animals are colour blind, and some (mainly nocturnal animals) cannot see any colour at all.
Below is an example of how most animals will see colours. Greens and red all are seen quite similarly as different shade of beige/ brown.
Interestingly, most animal coats are usually a brown/ red colour. To us, this would stand out if they were hiding in some long grass, but to most predators/ prey, its is pretty well camouflaged. in fact,Project Nightjar has only identified 2 predators which are trichromatic (able to differentiate between red and green), and one of those predators is humans!
Sloths can sometimes appear to be green, and this is caused by an algae which grows on their fur. This not only demonstrates a unique and creative way to develop green fur for camouflage, but also shows just how difficult it is to produce a green pigment in nature.
Green fur seems a logical camouflage to you and me, particularly because there is so much green foliage. However, the green pigment is very unique to the molecule chlorophyll, and almost never found in any other form throughout nature. Even frogs are not truly green.
The difficulty to produce ‘green’ is of little consequence to the natural world though. Most animals are red-green colour blind, and see most colours as a different shade of beige/ brown. This offers no significant advantage to being green, as seeing as beige/ brown / red colours are ‘easier’ to make in nature, most animal have evolved with this kind of colouring instead.
Image courtesy of Shandi-lee Cox
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Most predators are red-green colour blind, and so there is no advantage to being green over brown, because they are seen the same. Green is also a very rare pigment in nature, suggesting that the chances of an animal evolving such a pigment is very low.