Why Do Chameleons Change Color? Mood, Heat and Signals

Color as a message: mood, rivals and mates

For a chameleon, color is a language. Chameleons are solitary, territorial lizards, and changing color lets them settle disputes and find mates without wasting energy on fights.

When two male panther chameleons meet, both switch to their brightest colors, flatten their bodies sideways to look bigger and may gape and rock. Usually one male gives up, turns dark and drab and retreats, and the contest is over without a bite being exchanged.

A study of veiled chameleons at Arizona State University, published in 2013, showed how detailed these signals can be. Males whose side stripes became brighter were more likely to approach a rival, while males whose heads became brighter, and changed color faster, were more likely to win the contest. Different parts of the body seem to carry different information.

Females use color too. A receptive female panther chameleon shows pale, pinkish or green tones, but once she is carrying eggs she turns dark brown or black with orange stripes, telling males not to bother. Female veiled chameleons also darken and show stronger yellow markings after mating, and may gape or bite at a persistent male.

Research on South African dwarf chameleons supports the idea that signaling drives color change. When scientists compared species, those capable of the most dramatic color change were the ones with the most conspicuous social displays, not the ones living on the most varied backgrounds.

Color as a thermostat

Chameleons are cold-blooded: their body temperature depends on their surroundings. Color helps them manage it. A darker skin absorbs more sunlight and warms up faster, so many chameleons are dark early on a cool morning and turn paler as they heat up.

Desert chameleons show this clearly. The Namaqua chameleon of the Namib Desert in southwestern Africa turns black in the cool morning to absorb heat, then pale gray in the heat of the day to reflect sunlight. It can even be dark on one side and pale on the other, split neatly along the spine.

The skin also has a built-in sunshade. Deep in the skin, a second layer of reflective cells sends back much of the sun’s near-infrared light, the invisible part of sunlight that carries a lot of heat. This may help chameleons avoid overheating while they bask.

Camouflage: less than you think

Chameleons do rely on camouflage, but mainly through their ordinary resting colors. Greens, browns and grays, often with mottling, already blend with leaves and bark, and a chameleon that stays still is hard to spot. Their main defense against predators is to freeze and look like part of the plant.

Some species do adjust their colors when a predator appears. Smith’s dwarf chameleon of South Africa changes its colors differently depending on whether a bird or a snake is threatening it, matching the way each predator sees. Where predators are few, signaling can win out. On Hawaii, where Jackson’s chameleons were introduced and face fewer predators than in their native Kenya, the lizards use bold color changes for communication more and anti-predator changes less.

How does chameleon skin change color?

Chameleon skin has several layers of color cells, and the color you see comes from light passing through all of them:

The key discovery came in 2015, when researchers at the University of Geneva studied panther chameleons. They found that the upper iridophores contain nanocrystals of guanine arranged like a three-dimensional grid. In a calm chameleon the crystals sit close together and reflect blue light; filtered through the yellow pigment above, blue looks green. When the animal becomes excited, the cells change the spacing between the crystals, and the skin reflects longer wavelengths, so green shifts to yellow, orange or red within minutes.

Because this color is created by the structure of the skin rather than by pigment alone, it is called structural color, the same principle that makes a soap bubble shimmer. Darkening works differently: dark melanin pigment spreads through branching cells toward the surface and dims the colors above. Exactly how nerves and hormones trigger these changes is still being studied.

Which chameleons change color the most?

There are more than 200 chameleon species, and their color abilities vary widely:

• Big, colorful species such as panther, veiled and Jackson’s chameleons can show vivid greens, blues, yellows, oranges and reds, especially males during displays.
• Small leaf chameleons of the genus Brookesia live among dead leaves on the forest floor and mostly shift between shades of brown and tan.
• Forest species tend to have brighter, more varied palettes than chameleons of deserts and dry savannas, whose colors are mostly browns, grays and blacks.

Within a species, males are usually far more colorful than females, and young chameleons are often duller than adults.

Myths and facts about chameleon colors

Myth: chameleons can turn any color to match anything. Each species has a limited range of colors and patterns. A chameleon placed on a checkerboard or a tartan blanket does not copy the pattern.

Myth: color change is mostly for hiding. The evidence points the other way: the most dramatic changes are signals that make chameleons more visible, not less.

Fact: chameleons are not the only color changers. Cuttlefish, octopuses, flounders and anoles change color too. Cuttlefish use muscle-controlled pigment sacs and can change in a fraction of a second, much faster than any chameleon; see how cuttlefish change color and our list of animals that change color.

Fact: some chameleons glow. Many chameleons, especially in the Madagascar genus Calumma, have small bumps on the head where bone lies just under thin skin. Under ultraviolet light these bumps glow blue, a recently discovered feature that may also play a role in signaling.