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Why Is Blue So Rare in the Animal Kingdom?

Quick. Name all the blue animals you can think of. What did you come up with? A blue jay? Maybe a bluebird or an indigo bunting? Did you think of any blue animals that aren’t birds? Probably not, but that’s OK. There aren’t many blue creatures in the animal kingdom.

With the exception of blue jays and a few other birds, not many animals are blue. (Photo via Shutterstock)

Several birds common in Will County sport blue feathers, but not one animal on Earth with a backbone makes blue pigment. We see blue more frequently in plants because they have pigments called anthocyanins. But very few animals have the ability to make blue pigments.

Even when we see blue animals, like blue jays, the blue color is actually the result of a scientific phenomenon called Rayleigh scattering, which is the same phenomenon that makes the sky appear blue.

Blue jays are not actually blue. Instead, they appear that way to us because of Rayleigh scattering. Blue jays produce a pigment called melanin, which is brown or almost black in color. However, a blue jay's wings contain tiny pockets made of air and keratin, the same protein that makes up our hair and fingernails. When light hits these pockets in the blue jay's feathers, all the colors of the wavelength except blue are absorbed. The blue wavelength is refracted, which is what allows us to see the feathers as blue in color.

That same effect is what causes other blue birds, such as indigo buntings, eastern bluebirds and peacocks, as well as blue butterflies and moths, to appear blue. Without the prism-like structures in their wings, they would appear a dull brown color instead of a bright blue.

Not every shade of blue in the animal kingdom is a trick of the eye though. Some frogs are blue, and lizards too. And maybe you've seen flashes of blue on fish. Close to home, we have the blue-spotted salamander. The blue hues on these animals are also due to pigments, but not blue pigments. Instead, these animals have green and yellow pigments that give them a blue appearance because of how the different wavelengths of light are absorbed.

Some of the “blue” animals in the wild are just because of their names, not their color. Take blue whales. These giant creatures — the largest animals ever known to live on Earth — look blue underwater, but when they come to the surface it's clear they are gray.

There are a few living things that are true blue, like the Linckia laevigata sea star. These sea stars get their blue color from blue pigments, and they are one of the few creatures on Earth to truly have blue coloring. And a few creatures, lizards mainly, can turn themselves blue. For example, blue iguanas turn themselves blue only when they are around other members of their species. The Sinai agama lizard is normally brown, but the males will turn blue to attract a mate.


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