Why blue animals are so rare

>Organisms that appear blue must absorb very small amounts of energy, while reflecting high-energy blue light. Since penetrating the molecules that are capable of absorbing this energy is a complex process, the color blue is less common than other colors in the natural world.

I’m not a biologist, but these sentences immediately reminded me of reading articles about my company/technology after press briefings and feeling like they butchered a basic concept (or more correctly, I failed to explain it in an accessible way). Like, the sentences are grammatically correct but don’t make technical sense.

The linked post—<https://set.adelaide.edu.au/news/list/2019/08/20/why-is-the-...>—is much better about answering the question, rather than listing some examples.

Basically:

- Blue is rare in plants since it means leaving high energy behind.

- Many animals are a color because of there food, and see above.

- Thus, any blue is trickier, and usually done via scattering and mixing rather than a pigment. "The only exception in nature is the obrina olivewing butterfly, which is the only known animal to produce a true blue pigment."

The article mentions plants too. But I can list a number of blue plants in my vicinity (OK, sometimes a touch of purple too) or even in the garden:

[Centaurea cyanus](https://en.wikipedia.org/wiki/Centaurea_cyanus?wprov=sfla1)

[Digitalis](https://en.wikipedia.org/wiki/Digitalis?wprov=sfla1)

[Centaurea](https://en.wikipedia.org/wiki/Centaurea?wprov=sfla1)

[Scabiosa](https://en.wikipedia.org/wiki/Scabiosa?wprov=sfla1)

[Phacelia](https://en.wikipedia.org/wiki/Phacelia?wprov=sfla1)

and last but not least many varieties of [Campanula](https://en.wikipedia.org/wiki/Campanula?wprov=sfla1)

Here’s a good answer from SE: https://biology.stackexchange.com/questions/56476/why-are-so... (spoiler: we don’t know). But the second answer speculates that blue light was the most available to the ancestors of current plants (due to properties of Earth’s atmosphere) so they evolved to absorb it.

Related question is why plants are green: https://biology.stackexchange.com/questions/450/why-do-plant...

My favourite flower, which I have just discovered: Phacelia (blue/violet color) ( https://en.wikipedia.org/wiki/Phacelia_tanacetifolia )

1) Seeds easy to find in most stores.

2) Each strand has an array of flowers which bloom serially => quite long blooming timespan (and damage by bad weather is limited if it affected only the flowers).

3) Bumblebees absolutely love them (this year I put exclusively Phacelia seeds into 1 of my 2 big pots on the balcony, with max seed density, and often there were up to 10 bumblebees at once per pot checking them), and I absolutely love bumblebees (they look clumsy, they're kind of funny + they absolutely ignore me, respectively when they happen to fly in my direction and they notice me they take a turn as soon as their flight envelope allows them to)

4) This might be just random or caused by some other factor like weather/neighbours/whatever, anyway:

since I planted this year Phacelia flowers and the bumblebees started coming I have hardly seen any wasps nor especially hornets (I've seen twice a hornet flying by, but it took a large curve from my balcony - during the same timespan at the other sides of my flat I noticed four times hornets investigating in front of the windows). Last year (without Phacelia/bumblebees) I had a lot more problems with wasps&hornets => maybe wasps & hornets noticed the bumblebees and thought "ah, already taken/busy!" and therefore marked my balcony as a no-go zone?

EDIT:

I recommend the app "PlantNet" for Android ( https://play.google.com/store/apps/dev?id=829216199869931637... ) & iOS ( https://apps.apple.com/ch/app/plantnet/id600547573 ): take a picture of your plant/flower and you get the name.

Fascinating article. But early on I had one question - why is a blue that is made by sunlight hitting hair nanostructures considered a "simulation" thereby differentiating it from color made through sunlight interaction with biochemistry of surfaces and subsurfaces?

To draw that out further, by the same logic we might consider properties of human-made metamaterials also simulations?

On a related note, blue LEDs are also the most rare, for engineering reasons, and their production led to a Nobel Prize: https://www.nobelprize.org/prizes/physics/2014/press-release...

Reminder to everyone:

Plants are green(On earth) because they reflect the green color (which the sun spectrum is strongest) because they have probably adapted to better regulate different lightning condition during the day, for this they use two different pigments (chlorophyll a(blue), chlorophyll b(red); or other pairs)

My favorite blue animal:

https://duckduckgo.com/?t=h_&q=Dendrobates+Tinctorius+Azureu...

My cousin wrote a book about this topic (it is not only about blue animals but the general scarcity of blue in the natural environment): https://www.amazon.de/Blue-Science-Secrets-Natures-English-e...

I never gave this much thought before but the book quite successfully managed to interest me in its subject and lead to me understanding some of the underlying mechanisms (which lay all outside my domain as a software developer).

Reminds me of Truite au Bleu or blue trout. It’s a recipe for cooking fresh trout which supposedly originated in the Alps.

“Why Trout Is Turning Blue in an Old Garage in Queens”

It’s the best way to cook trout. You’re welcome.

https://www.vice.com/en/article/kbxdv9/why-trout-is-turning-...

Isn't it pretty common in marine animals?

Lots of fish, dolphins, whales, etc. Or do they count as grey?

Someone told me that chefs use blue bandaids, because there is no blue food.

Blue jays are a pretty easy example of structural coloration

Are blue animals rare? They are certainly not that rare as a casual search turns up hundreds of photos of blue lizards, butterflies, Beatles, spiders, birds, starfish, fish, whales, sharks, and other miscellaneous sea and land creatures.

As for animals, they need to avoid predators. I'd say that blue isn't the best color to hide in most areas. So selection should favor other colors, unless the color is used as a warning, e.g. to signal a poisonous creature.

"Unlike other bees, they prefer to live alone and not in busy hives. "

IIRC, the vast majority of bees are solitary (90%?)

Green snakes are technically blue. They have yellow pigments together with a blue scales.

After their death, the yellow pigments fade, leaving a blue husk of a snake.

There are also no blue pigments in any plant. The various blueish flowers use other tricks to reflect blue light.

While growing up in Asian country, butterfly pea plants with bright blue flowers were common.

Hmm, interesting. I thought it was like with popsicles, how the blue ones get eaten first.

Just saw a Blue Jay last week.

Chicory has nice blue flowers.

Both are common in Chicagoland.

I was hoping to see something about velella, they have a shockingly brilliant blue.

Weird that this website seems broken with an un dismissable popup on an iphone… not exactly a rare user device.

lots of blue birds

prompt to ChatGPT 4o:

there are very few blue colored animals. also it was very difficult to develop LEDs emitting blue colored light. are those two observations technically related? can you summarize the technical relationship in a paragraph of few sentences?

answer:

The rarity of blue color in animals and the difficulty in developing blue LEDs are technically related due to the higher energy associated with blue light. Producing materials or structures that can efficiently emit or reflect blue light is challenging because blue light has shorter wavelengths and higher energy, requiring precise and stable materials. In animals, this results in the reliance on complex structural coloration rather than pigments. Similarly, the development of blue LEDs required breakthroughs in materials science to create stable semiconductors capable of emitting high-energy blue light, such as gallium nitride.