Chameleons' Craziest Color Changes Aren't for Camouflage

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.
ByBenji Jones
Published August 2, 2018
• 8 min read
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 Tangled, 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.”
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.
Photograph by Christian Ziegler, Nat Geo Image Collection
Please be respectful of copyright. Unauthorized use is prohibited.
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.
Blending In
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.
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.”
In other words, chameleons can, in fact,change the color of their skin to match the environment, but within a narrow sliver on the color wheel. “Chameleons will have a limited repertoire,” she says. “But I have no doubt that within that they can change to match their environment.”
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.
Photograph by Christian Ziegler, Nat Geo Image Collection
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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.
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.
Photograph by Christian Ziegler, Nat Geo Image Collection
Please be respectful of copyright. Unauthorized use is prohibited.
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.”
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