Chameleon colours aren’t just camouflage, says Eli Greenbaum, an evolutionary geneticist at the University of Texas at El Paso—they also change due to temperature shifts or emotions.
And males get emotional when they see other males that could be rivals for females or habitat.
“Male chameleons will, in most cases, immediately change colours in response to seeing another male, and in this instance, to itself in a mirror,” says Daniel F. Hughes, a doctoral candidate in Greenbaum's lab.
To illustrate his point, he referred us to a YouTube video of a male panther chameleon, a species native to Madagascar, doing that very thing.
A male chameleon that sees a "rival" would get excited and change from its camo green to noticeable hues of yellow, orange, or even red, says Michel C. Milinkovitch, a biophysicist at the University of Geneva.
Colour Me Mad
In 2015, Milinkovitch and colleagues revealed the unique way these quick-change artists switch their colours.
Scientists had thought pigment-containing cells at the skin's surface control the changes. Instead, a lattice of nanocrystals within another skin cell layer alters to reflect light differently.
When the chameleons are calm, the nanocrystals are close together and reflect blue and green light, which gives the reptile its green colour.
Two male panther chameleons, displaying their warning red colour, battle in Madagascar [Image: Christian Ziegler, National Geographic Creative]
When agitated, however, the space between the nanocrystals increases.
This allows more light with larger wavelengths, such as bright red and orange, that make the male stand out to competitors.
Defeated males will darken in colour, which communicates "please leave me alone," according to a study led by Arizona State University's Russell Ligon. That's an important skill, as it's hard for these slow-moving animals to escape.
But what about the lizard ladies?
Females change colour to communicate their sexual status to males, Hughes says. Female Mediterranean chameleons, for example, display yellow spots to signal sexual receptivity, according to a 1998 study.
Female social signals may be fewer "because they choose and males are competing to be chosen."
And if she sees herself in a mirror? It would likely be more subtle than the male reaction, Hughes says—although there isn't enough knowledge of female chameleons to know for sure.
Following a fight for a female, the winning male panther chameleon puts on his victory colours, while the loser turns a drab brown [Image: Christian Ziegler, National Geographic Creative]
“Female-female communication in chameleons is generally not well understood,” he says, and may be less obvious than interactions between males.
Colour us humans envious of an animal who looks in a mirror and sees little that needs changing.