The Chatoyant Chameleon

Chameleons, with their unique ability to change color according to their surroundings, have long been considered masters of camouflage by public and scientific communities alike. But the chameleon’s fickle complexion has been found to have a much wider array of purposes.

Chameleons possess specialized cells in their skin that allow them to change color in response to environmental change. These pigment-bearing cells respond to a chameleon’s hormonal signals to alter the placement of melanin within the cell. Clumping the melanin together will cause the chameleon to appear lighter in color; distributing the melanin throughout the cell will cause the chameleon to appear darker. If this were the only mechanism at work, however, it would follow that chameleons had the ability to only darken or lighten their coloration.

In order to produce the full spectrum of hues at the chameleon’s disposal, these creatures are able to proportion the primary colors much like an artist would to create more advanced colors. Under their top layer of translucent skin, chameleon skin cells contain chromatophores, another type of pigmented cell. Chromatophores with yellow and red pigment are found among the top layers, while lower layer chromatophores contain blue or white pigment. As with melanin, these cells are hormone-signaled, and by enlarging or shrinking, change the outward appearance of a chameleon’s skin.

An understanding of the chameleon’s chatoyancy, however, does not disclose its evolutionary purpose. A study led by Devi Stuart-Fox of the University of Melbourne, gave results that suggest something contradictory to widespread textbook knowledge: chameleons evolved their color-changing abilities to stick out rather than blend in. If camouflage was the major evolutionary factor, then chameleon species with the most diverse habitat backgrounds would have the widest ability of skin coloration. But Stuart-Fox found, “no relationship between how much [chameleons] change color and the variety of backgrounds they had to match.” Rather, social communication seemed to be the driving evolutionary factor.

By changing the patterns of colors in their skin, chameleons are able to communicate with each other. Male chameleons will proclaim dominance by flashing bright colors, while submission is denoted by drab browns and grays. Females may change their coloration to reject or accept potential mates, or to communicate that they are pregnant. Such color alterations can happen quickly, in a matter of seconds, and the risk of predator response is minimal. The modern chameleon may also use this ability to lighten his skin on a bright day. Lighter colors reflect more sunlight and are one way for a cool chameleon to beat the heat.