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The rarity of blue -

In the animal kingdom, blue animals are incredibly rare compared to other colors. There are no blue tigers, bats, squirrels, or dogs, and even blue whales aren't truly blue. This rarity makes the few blue animals we find quite striking.

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Remarkable appearance -

Despite the rarity, when nature does produce blue creatures, they are stunning. Evolution has created these spectacular colors through fascinating mechanisms, and blue is never presented in a muted or halfway manner.

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Animal coloration -

To understand the uniqueness of blue, one must first understand how animals obtain their colors, which is usually for communication purposes. Butterflies serve as a prime example, since they showcase bright and varied patterns used for signaling.

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Color communication -

Butterflies use vibrant colors to convey messages, such as warning predators about toxicity or marking territories. Their colorful wings are a vivid tool for communication, which have evolved to fit into their active daytime lifestyle.

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Color coded -

Butterfly wings are made up of tiny scales, which produce colors in two ways: through pigments or structural features. Oranges, reds, and browns come from pigments that absorb all colors except the ones they display.

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Pigment-based colors -

Animals (including humans) are not able to produce most pigments on their own. Instead, they obtain these colors through their diet. For instance, flamingos (who are born gray) turn pink by consuming carotenoids found in crustaceans.

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Blue coloration -

Blue is a unique color because there are no natural blue pigments in most blue animals. Instead, blue colors are produced by the structure of the animal's body, which manipulates light to create the blue hue.

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Blue morpho butterflies -

The stunning blue of the blue morpho butterfly comes from the microscopic structure of its wing scales. These scales contain intricate shapes that manipulate light waves and only allow blue wavelengths to reach our eyes.

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Structural color -

The arrangement of tiny ridges on the butterfly wing scales makes light bounce in a way that only blue wavelengths remain. The microscopic structures act like a filter, canceling out other colors and enhancing the blue.

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Refraction -

The appearance of blue in a butterfly’s wings relies on light bending when it transitions from air to the solid material of the wings. If the microscopic gaps in the wing structures of the butterfly are filled with a liquid (such as alcohol), the color vanishes as the light no longer bends correctly.

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Water resistance -

Despite this delicate structure, the blue morpho butterfly’s wing scales are water-resistant, allowing them to maintain their vivid color even in the humid rainforest environment. This adaptation is crucial for survival.

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Bird feathers -

Birds, like blue jays, also exhibit blue colors created through structural manipulation. Their feathers contain microscopic beads that scatter light in a way that only blue wavelengths remain, not through any pigment.

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Light scattering -

Unlike the ordered structure of butterfly wings, the microscopic arrangement in bird feathers resembles a foam. This more random structure ensures the blue color appears consistent from various viewing angles.

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Peacock feathers -

Peacock feathers also don’t use pigment, and instead showcase an ordered, crystal-like structure. This arrangement reflects light brilliantly, giving their blue hues a more intense and iridescent quality.

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Mammals and monkeys -

Some mammals, like certain monkeys, have blue colors created by skin structures that manipulate light waves. Similarly, they are formed without any actual blue pigment.

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Blue eyes -

Even blue human eyes are a result of light-scattering structures in the iris rather than any blue pigment. Outside of the ocean, no vertebrate (whether bird, mammal, or reptile) produces blue pigment. The blue we see in these animals is entirely due to structural coloration.

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One true pigment -

Only one known butterfly species, the olivewing, has managed to produce an authentic blue pigment. This rare adaptation sets it apart, but little is known about how this unique evolutionary development came about.

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Evolution -

Scientists are unsure why blue is so rare in animals, but they speculate that ancient birds and butterflies evolved to see blue long before they could produce it. The development of blue structures was a significant evolutionary leap, and opened new ways to communicate and survive.

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The challenge -

Creating a blue pigment would have required animals to change their bodies using complex new chemistry. Ultimately, evolution found it easier to subtly alter the microscopic shapes of animals’ bodies to produce blue through structural means.

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Engineering -

Animals solved the challenge of creating blue not with new biological pigments, but through engineering. By shaping the surfaces of their bodies to bend light, they ingeniously made blue colors using physical principles.

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Color spectrum -

Another reason why blue is so rare in nature is because of the limited color spectrum that most animals can see. Many mammals (including cats and dogs) can only see a small amount of color, and they tend to see only pastel shades of blue and yellow.

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Flora -

But the animal kingdom isn’t the only place in nature where blue is a rarity; flora have been known to lack this color as well. But unlike animals, plants are actually able to produce pigments on their own. In fact, they’re renowned for it. So why is blue still so scarce?

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Blue leaves and petals -

Blue flowers are incredibly rare in plants, and there is virtually no plant in the world that has blue leaves. The only ones that can be found would be on the floor of tropical rainforests.

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Chlorophyll -

The color of pigments that people see on plants is made by the color of light that has been reflected and not absorbed. The most common plant pigment is green chlorophyll, and so plants look green because chlorophyll reflects and does not absorb green light.

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Blue light -

Plants love blue light, because it has far more energy than any other light on the visible spectrum. This is why plants won’t produce blue pigment, because doing so would mean that they reflect blue light instead of absorb it, which would limit their growth.

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Robert Hooke -

In the 1600s, English physicist Robert Hooke observed peacock feathers with one of the first microscopes and described the colors as “fantastical.” His fascination marked the beginning of a long scientific journey to understand colors and their structures.

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Isaac Newton -

Even Isaac Newton (often considered to be the father of physics) was fascinated by the unusual properties of blue in nature. His observations contributed to the scientific understanding of light and optics.

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In history -

The earliest use blue dye can be dated to approximately 6,000 years ago, when the ancient Egyptians created a long-lasting blue pigment known as irtyu using copper oxide, calcium oxide, and silica. Blue is such a rare color that many viewed it as a color of high status for thousands of years.

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Precious color -

Lapis lazuli was often ground into a vivid blue pigment known as ultramarine, and it was as precious as gold in medieval Europe. As such, it was primarily reserved for illustrating illuminated manuscripts.

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Modern scientific studies -

Today, scientists continue to study blue coloration, not just for the physics but for the beauty. The intricate relationship between light, structure, and color remains a subject of both scientific and aesthetic fascination.

Sources: (Live Science) (The University of Adelaide) (Popular Science) (HT School)

See also: How colors affect our mood and emotions

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