Chameleons’ Craziest Color Changes Aren’t for Camouflage

Despite what a widespread myth and fake videos suggest, the creatures have an unexpected motivation to show their most brilliant colors.

Some people are like chameleons: They can blend into any environment with ease. But are chameleons, themselves, like. chameleons?

Yes, and no, scientists say. Contrary to a widely held belief—bolstered by the likes of Disney’s запутанный, which co-stars a chameleon named Pascal—these enigmatic lizards cannot transform the color of their skin to match any background.

“People believe that if you put a chameleon on chessboard it’s going to hide by taking the same pattern or color, but this is of course is not true,” says Michel Milinkovitch, an evolutionary geneticist at the University of Geneva and an expert on animal skin color.

And videos on YouTube, he says, some of which show the lizards changing colors as they encounter different surfaces or objects, “are completely fake.”

Nevertheless, a chameleon’s hue-shifting skills are some of nature’s best—and most multifaceted. (Related: See how chameleons change colors)

A male and a female Decary’s leaf chameleon, Brookesia decaryi. Most chameleons have skin that already resembles their environment, but they can adjust the brightness of the hue in varioius ways.

Though incapable of matching certain details in their environments, such as bright flowers or individual blades of grass, chameleons can, in fact, make small color adjustments to blend into their surroundings. And the more dramatic color transformations—which have made species like the panther chameleon famous—help these lizards defend territory and attract mates.

So while they may not live up to their common portrayal in entertainment media, their use of color is far more impressive than most people imagine. Let’s take a closer look.

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Chameleons are often nearly impossible to see—just ask anyone who’s spent time in the field looking for them. “It’s incredibly difficult to spot them,” Milinkovitch says.

And there’s a good reason for it: These lizards are utterly defenseless. They don’t have a dangerous bite, their skin isn’t packed with poison, and they can’t move quickly. Staying hidden is pretty much their only tactic to evade predators.

THE ILLEGAL, SECRETIVE WORLD OF CHAMELEON RANCHING

Much of the “blending in” chameleons do doesn’t require color change at all, Milinkovitch says. In their natural state, they already look a lot like leaves or branches, much like stick insects looks like. sticks. (See also: Inside the secretive world of Florida’s chameleon catchers)

But these lizards do have the ability to adjust how bright their skin appears, says Devi Stuart-Fox, an evolutionary biologist at the University of Melbourne, who’s been studying chameleon color for more than a decade.

When there’s less light, she says, such as on a tree deep inside a Malagasy forest, brown to black pigment cells called melanin flood to the skin’s surface and cause the chameleon to appear darker—and thus more camouflaged.

“It’s like putting a dark wash on everything,” Stuart-Fox says. “You’ve got to imagine paint mixing: If you have green paint and mix more black into it, it will change the brightness and also the hue.”

Другими словами, хамелеоны действительно могут менять цвет своей кожи в соответствии с окружающей средой, но в узком диапазоне цветового круга. «Хамелеоны будут иметь ограниченный репертуар», — говорит она. «Но я не сомневаюсь, что внутри этого они могут измениться, чтобы соответствовать своей среде».

The more elaborate displays, such as when multiple, bright colors appear at once, are saved for another purpose entirely.

A Parson’s chameleon, Calumma parsonii, in Madagascar. Chameleons’ reserve their most impressive color-changes for mating and competition.

A Show of Strength

Chameleons have two opposing states, Milinkovitch says. They either try to be invisible, which subtle color shifts help them achieve, or try to be seen—again by changing their color, but this time much more explosively.

No display stands out against the green forest backdrop like that of male dominance. Chameleons are highly territorial: When two males encounter each other, there’s a fierce show-off—in this case, of color.

“They go nuts,” Milinkovitch says. “They’ll become yellow, red, white—something visible in the tree.”

The weaker male, who’s often smaller and more dimly colored, will concede defeat by turning off his display first, which indicates that he doesn’t want to fight.

Perhaps he’ll try another tactic instead. Research has shown that some male chameleons will use color to impersonate females, which allows them to sneak by other males without the threat of competition, much like cuttlefish have been known to do.

Chameleons will also use their displays to dazzle females during courtship. But no matter how brilliant the display, some female lizards won’t be interested—and they’ll use color to let the men know.

Impressing, Repelling

“The female will react, depending on whether or not she’s available,” Milinkovitch says. If she already has the sperm of another male in her reproductive tracks, he says, “then she’s going to become very dark, and very aggressive.”

Males can be violent, he says, so it’s important that females avoid them if they have no need for insemination. If the female is available she won’t show much color and instead remains a greenish-brown, Milinkovitch says, indicating submission.

A Malagasy giant chameleon, Furcifer oustaleti, in its native habitat in Kirindi National Park, Madagascar.

Stuart-Fox believes that changing color may serve yet another, albeit poorly-researched, function: Helping chameleons regulate their body temperature. This trait is widespread among lizards—in a 2016 study, she showed that bearded dragons can alter their skin color based on temperature—and so it’s unlikely that chameleons wouldn’t also have this ability, she says.

Chameleons are ectotherms, she says, and so they can’t retain heat generated from their metabolism. Instead, they have to warm up using the sun. (That’s why you see lizards basking on rocks in the early morning when it’s cold).

Darker colors absorb more light, and chameleons have likely evolved to capitalize on this principle, she says. When it’s cold and the sun is up, they wash themselves with melanin to darken and thus accelerate warming—unless the color makes them stand out, that is.

The ability to change color first likely evolved in chameleons for camouflage, Stuart-Fox says, but the talent now satisfies a wide range of these animals’ needs, like temperature control.

In some cases, the talent satisfies multiple needs at once. In 2003, Stuart-Fox came across Smith’s dwarf chameleon basking on a dark-colored flower stalk while doing field work in South Africa. “It’s perfectly camouflaged,” she says, while also able to “absorb maximum sun.”

“I just think that animals never cease to surprise us in how they can achieve multiple things at once and get the best of all worlds.”

Objects can now change colors like a chameleon

Computer Science and Artificial Intelligence Laboratory team creates new reprogrammable ink that lets objects change colors using light.

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PhotoChromeleon, a reversible process for changing the color of objects developed at MIT, involves a mix of photochromic dyes that can be sprayed or painted onto the surface of any object.

“By giving users the autonomy to individualize their items, countless resources could be preserved, and the opportunities to creatively change your favorite possessions are boundless,” says MIT Professor Stefanie Mueller.

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The color-changing capabilities of chameleons have long bewildered willing observers. The philosopher Aristotle himself was long mystified by these adaptive creatures. But while humans can’t yet camouflage much beyond a green outfit to match grass, inanimate objects are another story.

A team from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) has brought us closer to this chameleon reality, by way of a new system that uses reprogrammable ink to let objects change colors when exposed to ultraviolet (UV) and visible light sources.

Dubbed “PhotoChromeleon,” the system uses a mix of photochromic dyes that can be sprayed or painted onto the surface of any object to change its color — a fully reversible process that can be repeated infinitely.

PhotoChromeleon can be used to customize anything from a phone case to a car, or shoes that need an update. The color remains, even when used in natural environments.

“This special type of dye could enable a whole myriad of customization options that could improve manufacturing efficiency and reduce overall waste,” says CSAIL postdoc Yuhua Jin, the lead author on a new paper about the project. “Users could personalize their belongings and appearance on a daily basis, without the need to buy the same object multiple times in different colors and styles.”

PhotoChromeleon builds off of the team’s previous system, “ColorMod,” which uses a 3-D printer to fabricate items that can change their color. Frustrated by some of the limitations of this project, such as small color scheme and low-resolution results, the team decided to investigate potential updates.

With ColorMod, each pixel on an object needed to be printed, so the resolution of each tiny little square was somewhat grainy. As far as colors, each pixel of the object could only have two states: transparent and its own color. So, a blue dye could only go from blue to transparent when activated, and a yellow dye could only show yellow.

But with PhotoChromeleon’s ink, you can create anything from a zebra pattern to a sweeping landscape to multicolored fire flames, with a larger host of colors.

The team created the ink by mixing cyan, magenta, and yellow (CMY) photochromic dyes into a single sprayable solution, eliminating the need to painstakingly 3-D print individual pixels. By understanding how each dye interacts with different wavelengths, the team was able to control each color channel through activating and deactivating with the corresponding light sources.

Specifically, they used three different lights with different wavelengths to eliminate each primary color separately. For example, if you use a blue light, it would mostly be absorbed by the yellow dye and be deactivated, and magenta and cyan would remain, resulting in blue. If you use a green light, magenta would mostly absorb it and be deactivated, and then both yellow and cyan would remain, resulting in green.

After coating an object using the solution, the user simply places the object inside a box with a projector and UV light. The UV light saturates the colors from transparent to full saturation, and the projector desaturates the colors as needed. Once the light has activated the colors, the new pattern appears. But if you aren’t satisfied with the design, all you have to do is use the UV light to erase it, and you can start over.

They also developed a user interface to automatically process designs and patterns that go onto desired items. The user can load up their blueprint, and the program generates the mapping onto the object before the light works its magic.

The team tested the system on a car model, a phone case, a shoe, and a little (toy) chameleon. Depending on the shape and orientation of the object, the process took anywhere from 15 to 40 minutes, and the patterns all had high resolutions and could be successfully erased when desired.

While PhotoChromeleon opens up a much larger color gamut, not all colors were represented in the photochromic dyes. For example, there was no great match for magenta or cyan, so the team had to estimate to the closest dye. They plan to expand on this by collaborating with material scientists to create improved dyes.

“We believe incorporation of novel, multi-photochromic inks into traditional materials can add value to Ford products by reducing the cost and time required for fabricating automotive parts,” says Alper Kiziltas, technical specialist of sustainable and emerging materials at Ford Motor Co. (Ford has been working with MIT on the ColorMod 3-D technology through an alliance collaboration.) “This ink could reduce the number of steps required for producing a multicolor part, or improve the durability of the color from weathering or UV degradation. One day, we might even be able to personalize our vehicles on a whim.”

Jin and Mueller co-authored the paper alongside CSAIL postdocs Isabel Qamar and Michael Wessely. MIT undergraduates Aradhana Adhikari and Katarina Bulovic also contributed, as well as former MIT postdoc Parinya Punpongsanon.

Adhikari received the Morais and Rosenblum Best UROP Award for her contributions to the project.

Ford Motor Co. provided financial support, and permission to publish was granted by the Ford Research and Innovation Center.