We know that blue is a rare color in nature and that most animals get their colors from pigments in their food. However, blue seems to be different. There are no blue tigers, no blue bats, no blue squirrels, or blue dogs. Even blue whales aren’t that blue. Yet, when we do find a blue animal, they’re awesome looking. Nature doesn’t do halfway with blue. In this article, we are going to journey through evolution, chemistry, and some very cool physics to understand why this is so.
Understanding Animal Colors
To understand why animals have colors, we need to look at butterflies. Bob Robbins, the curator of Lepidoptera at the National Museum of Natural History in Washington D.C, calls butterflies awesome. They’re a group of moths that evolved to be active during the day, which gives them an advantage of using light to communicate. Out of all insects, butterflies display the brightest and most detailed patterns. The colors in butterfly wings deliver messages, like “I’m toxic”, or “I’m a male and this is my territory”. These colors come from tiny scales, which contain pigments that absorb every color except what we see. Animals, from butterflies to birds to humans, don’t make these pigments from scratch; they’re made from ingredients in our diet. Flamingos turn pink thanks to pigments called carotenoids in crustaceans they eat.
The Unique Case of Blue
However, blue is different. The Blue Morpho butterfly is one of the most beautiful butterflies in the world, and it is blue, but it doesn’t have any blue pigments. The blue color comes from the shape of the wing scale itself. The microscopic structure of the wing scatters the blue light, while absorbing all the other colors. This is why Blue Morpho butterflies appear to change color as we move the camera. The color changes are like a hologram thing, as there is no blue pigment in these butterflies.
If we zoom way in on a blue wing scale, we see these little ridges that are shaped like tiny Christmas trees. When light comes in, some bounces off the top surface, but some light passes into the layer and reflects off the bottom surface. For most colors of light, waves reflecting from the top and bottom will be out of phase, and that light is removed. But blue light has just the right wavelength; the reflected light waves are in sync, and that color makes it to our eye. The arrangement of the branches is what gives Morpho wings their blue color.
Peacock feathers, blue jay feathers, and even blue eyes also get their colors from structures, not pigments. Outside of the ocean, almost exclusively, the bluest living things make their colors with microscopic structures, and each one’s a little different. No vertebrate, not a single bird or mammal or reptile that we know of, makes a blue pigment on its body. Blue as a pigment in nature is incredibly rare.
Why is Blue Rare in Nature?
The best theory so far for why blue is rare in nature is that at some point way back in time, birds and butterflies evolved the ability to see blue light, but they hadn’t yet evolved a way to paint their bodies that color. If they could, it would be like going from early Beatles to Sgt. Pepper’s Beatles. It meant new opportunities for communicating and survival. Creating some blue pigment would have required inventing new chemistry, and there was no way to just add that recipe to their genes. It was much easier for evolution to change the shape of their bodies, ever so slightly, at the most microscopic level, and create blue using physics instead. In a way, they solved a biology problem with engineering.
What is fascinating about blue is that it has intrigued curious people for hundreds of years. Robert Hooke, after looking at peacock feathers through one of the first microscopes back in the 1600s, wrote, “these colours are onely fantastical ones”. Even Isaac Newton noticed there was something unusual about these blues, and scientists have been studying it ever since. Not only because the science is interesting, but because it’s beautiful.
In conclusion, blue is a rare color in nature, and the bluest living things make their colors with microscopic structures. No vertebrate, bird, mammal, or reptile that we know of makes a blue pigment on its body. Blue is created through physics instead of chemistry, which makes it different from other colors. Evolution has solved the problem of creating blue through slight changes in the microscopic structure of animals. Blue in nature is not only rare, but it’s also beautiful, which has fascinated curious people for hundreds of years. Understanding how blue is created in nature is an important step in understanding how nature works and how evolution has solved problems in unique ways.
Thank you for reading this article on the rarity of blue in nature. We hope that this has been an informative and interesting read. If you have any questions or comments, please feel free to reach out to us.