Why are there no green-haired mammals? Do they just not like them?

Audit expert: Wang Lei

PhD in Ecology, Beijing Forestry University

National Parks and Reserves Researchers

We often see green plants, green insects, and green birds, but have you ever seen green mammals ?

It stands to reason that mammals like tigers, lions, and rabbits often live in forests or grasslands. Their colors are too conspicuous, so if they had green fur, they would be more concealed! However, they are still not green. Why is that? Do mammals living in the forest do not need protective colors? Or are they so strong that they don't need protective colors?

Want to be green? I don't have the conditions. In nature, there are many green animals, such as frogs, lizards, mantises, etc. Most of the time, they are all green. But mammals such as tigers, cats, and dogs seem to have nothing to do with green hair. Do they dislike it? Do they not want it? No, neither! These mammals themselves do not have the conditions!

#Only eumelanin and pheomelanin

In nature, some green animals synthesize green pigments by themselves, such as caterpillars and mantises, while mammals generally only have eumelanin and pheomelanin .

Eumelanin can make mammals' hair appear dark brown, while pheomelanin can make skin and hair appear brown or orange. Combined with the albino gene, mammals' hair can only produce three basic colors: black, brown, and white. Black, brown, and white can only be mixed to produce gray, brown, chestnut, brown, orange, khaki, etc. It is impossible to mix green , blue , purple , cyan , pink , etc.

It could be said that mammals are genetically destined not to have striking green hair.

You may ask, "I think piglets are pink!" In fact, the pink color of pigs is the color of their skin , not the pink fur.

You might also say, "Sloths are mammals, so they are green!" In fact, all the green is moss, because sloths are so lazy! This is also the only wild animal with plants growing on its body .

#Using the diffraction of light

Although some animals in nature cannot synthesize green pigments, they use their own yellow pigments and the blue light diffracted by the crystals of their epidermal cells to mix and superimpose to display green , such as frogs. However, mammals have fine fur that is not as easy to diffract as bird feathers and cannot diffract blue light, so this method cannot be used to produce green.

Must we turn green? It seems unnecessary...

Let's get back to the topic. Although mammals cannot turn green by their own "efforts", it does not seem to prevent lions and tigers, which are mammals, from dominating the forest. This is because almost all mammals are color blind! And most of them are red and green color blind .

#Night Vision

As we all know, cats have very strong night vision. In fact, not only cats, but many mammals have very strong night vision. This is related to the lifestyle and natural history of their ancient ancestors.

In contrast, the ancestors of mammals did not live a very comfortable life most of the time. Instead, in order to avoid larger and more dangerous dinosaurs, they usually lived in hidden places, such as caves or underground, and waited until dark before they came out to hunt. Gradually, their sense of smell became sharper and they gained night vision, but their ability to distinguish colors also decreased.

#Dual Color Vision

We mentioned earlier that mammals mostly lived in caves or underground in the past. It was not until primates learned to climb trees that an accidental genetic mutation planted the gene for trichromatic vision in the monkey family. This is how humans' trichromatic vision came about.

But this gene is not stable enough, accounting for only about 94% of humans today, and the other 6% are still dichromatic, that is, red-green color blindness. In other words, red-green color blindness is the traditional gene, and trichromatic vision is a variant.

Comparison of color vision between humans and dogs

Through the above "Color Vision Comparison between Humans and Dogs" picture, you may not be able to intuitively feel the difference, so let's continue reading.

The picture below shows a tiger from the human’s perspective. It is orange in color and hiding in green leaves. It is too eye-catching. I’m afraid other small animals may not see it!

Let's take a look at what tigers look like in the eyes of mammals.

If you were a rabbit, you might not be able to see that the king of beasts is not far away.

From this point of view, there seems to be no need for mammals to turn green. Their own color is their best protective color.

Gene mutation creates green-haired mammal?

Will mammals have a gene mutation one day and develop green hair? What we need to know is that gene mutation is actually random and directionless, but only through natural selection can the mutated traits be preserved and inherited.

Judging from the current level of evolution of mammals, the absence of green mammals just proves that green hair does not bring any advantage to mammals in the survival of the fittest, and remaining unchanged may be the best way for them to survive.

Reference Materials

Chongqing Association for Science and Technology "Why are there no green mammals? | A little-known fact"

China Science and Technology Museum "Why are there no green mammals?"

Shida Biological Association "Why are there no green mammals?"

Shaanxi Natural History Museum "International Sloth Day, Let's Slow Down...Live Together..."