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Why don't animals have green camouflage?

"There's one mammal with green fur, but it's cheating," a researcher says.

Wouldn’t it make sense for a hare to blend in better with its surroundings? By being green, for example?

(Photo: Kieran Doherty / NTB Scanpix)

Ingrid Schou Ingrid Schou Ingrid Schou journalist

Published 6 February 2026 - 00:01

Blending into nature can mean the difference between life and death for animals.

So why aren't mammals green, making them harder to spot in grass and forests?

The explanation comes down to which colours bodies are actually able to produce – and that the world doesn't look the same to everyone.

"First, we have to understand where colours in animals come from," says Kjetil L. Voje.

He is an evolutionary biologist and studies how animals have become the way they are.

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"They mainly come from three places," he says.

Group of zebras standing in tall dry grass, facing the camera in a savannah setting — Some mammals, like zebras, have striking patterns in their fur. Researchers don't always know exactly why these developed, but they believe the patterns provide certain advantages.

A sloth clinging to a mossy tree branch in the forest canopy — "The sloth can actually have green fur. But it's cheating. Lots of tiny green algae grow in its fur, giving it that colour," says researcher Kjetil L. Voje.

More or less pigment

Mammals with fur or hair rely on a pigment called melanin.

You may have noticed that mammals share the same basic colour range as human hair.

That's no coincidence: "Humans are mammals too," says Voje.

Melanin protects us from dangerous UV rays from the sun. It can only produce a few colours: black, brown, yellow, and reddish tones.

Colour illustration of a crested pterosaur head and neck against a dark sky — Archaeologists have found feathers on flying reptiles and dinosaurs, suggesting that many of them may have been vividly coloured.

All the colours of the rainbow

Birds, fish, insects, and amphibians, on the other hand, can have ever colour of the rainbow – including green.

But these colours often don't come from pigments.

"The colours can come from tiny structures on their surface," says Voje.

Kjetil L. Voje is an evolutionary biologist.

These structures bend and split sunlight, much like the shimmering reflections you see in soap bubbles or on CDs.

"The blue tit is a good example," says Voje. Its feathers bend light in a special way, making the bird appear blue.

This is also why researchers think dinosaurs may have been colourful: Fossils show they had feathers, and feathers make these colours possible.

By contrast, mammalian hair and fur can't interact with light in the same way.

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You don't turn green from eating spinach

Flamingoes are pink because their favourite food is pink: small crustaceans called sea monkeys.

Humans and other mammals, however, can eat endless amounts of grass or spinach without ever turning green.

"There simply aren't that many ways for mammals to produce colours," says Voje.

Green simply isn't part of our colour palette.

Greater flamingos standing and feeding in shallow reflective water with green trees in the background. — Flamingoes are pink because their favourite food is pink: small crustaceans called sea monkeys or brine shrimp.

But isn't camouflage important?

Camouflage helps mammals avoid being eaten by predators and also allows them to approach their prey without being detected.

"It's been so important for survival that it explains the fur colour of many animals," says Voje.

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Even so, mammals have done fine without green. Few species spend much time high up in leafy treetops, Voje points out.

"The ground is usually brown, so being brown has worked just as well," says Voje.

There's also another important point:

"Different animals see colours in different ways," says Voje.

To humans, a brown hare stands out in a green field.

"But animals have their own way of seeing the world. If your predators can’t see green very well, then being green may not help you hide," says Voje.

In other words, brown can be just as effective for camouflage. Still, there is a green mammal out there.

Blue tit perched on a tall dried plant against a blurred green background. — In many species, bright colours are created by sunlight interacting with the body. "The blue tit is a good example," says Voje. Its feathers bend the light in a special way, making it look blue.

Cheating with algae

"There's one mammal with green fur, but it's cheating. Sloths appear green because their fur is home to lots of tiny green algae," says Voje.

The researcher doesn’t think the green colour has given the sloth any particular advantages.

Predators like jaguars and pumas aren't very good at distinguishing colours. T They respond mainly to movement, so the sloth’s slow movements may be the real advantage.

A stripy mystery

Some mammals' fur have striking patterns. Researchers don't always know why these evolved, but they suspect the patterns offer certain benefits.

Zebra stripes are one such mystery.

"There's a theory that the stripes confuse biting flies," says Voje. Fewer insect bites could mean fewer diseases.

The stripes may also make it harder for predators to focus on a single animal. Facing a moving black-and-white 'wall' could be more intimidating than spotting one clear target.

A third theory is that the white stripes help keep zebras cooler.

"But we don't actually know for sure," says Voje.

———

Translated by Alette Bjordal Gjellesvik

Read the Norwegian version of this article on ung.forskning.no