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.)