A Wildlife Article from All-Creatures.org

The Secret Behind Tigers' Orange Coloring

FROM PAWS Performing Animal Welfare Society
April 2022

Most mammals, including tigers, have dichromatic vision. This means they have only two cones: blue and green. Therefore, they cannot distinguish between red and green shades. In humans, this is known as color deficiency or “color blindness.” What does dichromatic vision have to do with helping tigers catch their prey? The mammals they prey on, such as deer and boar, also have dichromatic vision. This means they see the tigers’ orange coloring as shades of green, making it harder to detect the big cats and allowing tigers to better camouflage themselves in the forest. This gives tigers a greater chance of successfully securing a meal.

Nimmo

The tiger habitats at ARK 2000 are designed with the tigers in mind, so they feature an abundance of trees, shrubbery, grass, and other native vegetation. This provides a more natural and stimulating environment as well as privacy for these naturally elusive big cats.

When passing by the habitats you may sometimes spot a tiger – like Rosemary and Morris – but at other times they’re harder to find. When you do see a tiger, the bright orange color of their fur clearly stands out.

Rosemary and Morris

Tigers are ambush predators and they rely on invisibility in order to catch prey. Their black stripes make sense as they can blend into foliage and changes in light and shadow. But doesn’t that vivid orange color blow their cover? The answer has to do with how prey animals see tigers – which is very different from the way we perceive them.

Humans have what is called trichromatic color vision. Our eyes use two types of photoreceptor cells to see: rods and cones. Rods sense differences in light and dark. Cones register color. Humans have three cones: blue, green, and red. This allows us to see these colors and combinations of them. Great apes and monkeys also have trichromatic vision, as do marsupials. Birds and goldfish (and probably other fish) have four color cones.

Most mammals, including tigers, have dichromatic vision. This means they have only two cones: blue and green. Therefore, they cannot distinguish between red and green shades. In humans, this is known as color deficiency or “color blindness.”

What does dichromatic vision have to do with helping tigers catch their prey? The mammals they prey on, such as deer and boar, also have dichromatic vision. This means they see the tigers’ orange coloring as shades of green, making it harder to detect the big cats and allowing tigers to better camouflage themselves in the forest. This gives tigers a greater chance of successfully securing a meal.

These images simulate how prety animals see them (left) and how we see tigers (right), demonstrating the striking effectiveness of tiger coloration and the camouflage it provides. Photos courtesy of Journal of the Royal Society Interface.

Now imagine a white tiger – a rarity in nature that is the result of a genetic mutation. Without their orange-hued fur, these tigers have no camouflage and would be unable to successfully catch prey to survive. White tigers in captivity are produced through inbreeding, which often results in serious genetic abnormalities and lifelong health problems. Despite this, white tigers are exploited as a novelty in zoos, circuses, magic acts, and roadside attractions. Regardless of what unscrupulous exhibitors might tell you, tigers with this rare coat coloration have absolutely no conservation value, meaning they do not help save wild tiger populations.

Because both tigers and their prey cannot differentiate between orange and green, there is no evolutionary pressure for deer, for example, to develop green fur to better hide from a tiger or other predator. In fact, there are no mammals with green fur (sloths sometimes appear green, but the color is due to alga growing in their fur). So, expect nature to stay the course – and let’s consider ourselves lucky that we are able to see tigers’ distinctive colors as we do.

(This article is based on a study by Fennell et al. (2019) that appeared in Journal of the Royal Society Interface.)

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