If you’re creeping around in the forest trying to hunt your prey, one would imagine that a bright, striped orange coat would hardly be the best choice to blend into the background.
But as it turns out, the orange fur of a tiger is the perfect choice of camouflage for the predatory feline—even if this seems counterintuitive for humans who can see red, blue and green colors.
According to new research, deer—the main prey of tigers—are only capable of seeing blue and green light, rendering them color-blind to red. This means that tigers are effectively green, giving them an ideal cover against the backdrop of forests and canopy jungles.
The study by the University of Bristol used a computer simulation to perceive the world through the eyes of a “dichromat”—those animals who are unable to tell the difference between red and green.
This was done by generating images of red objects against a range of backgrounds, including the dense forest of tigers’ natural habitat, according to The Daily Mail, where the tigers were found to be perfectly camouflaged.
Study lead Dr. John Fennel, writing for the Royal Society Journal Interface, explained:
“The tiger appears orange to a trichromat observer rather than some shade of green, though the latter should be more appropriate camouflage for an ambush hunter in forests.
However… when viewed by a dichromat, the tiger’s color is very effective.”
The theory was then tested on a range of humans, who were shown images in which red objects were inserted in two different backdrops. One background displayed a temperate forest in Britain, while the other displayed semi-arid desert land in Spain.
Fennel and his team then measured the time it took for observers to detect the red sphere against each backdrop in the images as a means to replicate three-color (trichromatic) and two-color (dichromatic) vision.
Study participants were far quicker at detecting the images with three colors in each scenario.
So if mammalian predators are so keen on blending into the forest, why haven’t they evolved to grow green fur?
According to Fennel and his team, such a feat is impossible as it would “require a significant change to mammalian biochemistry.”
In the tiger’s case, the orange color in its fur is a result of a natural chemical it produces called pheomelanin.
And the reddish tones of tigers vary greatly across the globe, with Bengal tigers displaying brilliant reddish tones while Amur tigers appear far more golden than orange. In the northern regions such as Russia and northern China, tigers tend to have lighter coats while those in South Asia are darker.
In fact, only one type of mammal actually has green fur: the sloth. And that’s not because of any natural pigmentation, but because green algae grows on the sluggish creature.
Fennel and his team aren’t sure exactly why deer never evolved to possess the trichromatic vision that would have allowed them to spot the tigers better and avoid becoming their meal. According to him, this remains an “open question.”
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