Biologists at Arizona State University have discovered that veiled chameleons (Chamaeleo calyptratus) change colors in unusual ways when they interact with other chameleons.

In their study, Dr Russell Ligon and Dr Kevin McGraw used photographic and mathematical modeling tools to learn how the color change of veiled chameleons relates to aggressive behavior.

They studied the distance, maximum brightness and speed of color change of 28 different patches across the chameleons’ bodies.

“We found that the stripes, which are most apparent when chameleons display their bodies laterally to their opponents, predict the likelihood that a chameleon will follow up with an actual approach. In addition, head coloration – specifically brightness and speed of color change – predicted which was lizard was going to win,” said Dr Ligon, who is the first author of the paper published in the journal Biology Letters.

Chameleons typically have resting colors that range from brown to green, with hints of yellow, but each chameleon has unique markings.

During a contest, they show bright yellows, oranges, greens and turquoises. Interestingly, when they showed-off their stripes from a distance and followed that display with a ‘head-on’ approach before combat, the important color signals on the striped parts of the body and head were accentuated.

“By using bright color signals and drastically changing their physical appearance, the chameleons’ bodies become almost like a billboard – the winner of a fight is often decided before they actually make physical contact,” Dr Ligon said.

“The winner is the one that causes its opponent to retreat.”

“While sometimes they do engage in physical combat, these contests are very short – 5 to 15 seconds.”

“More often than not, their color displays end the contest before they even get started.”

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Russell A. Ligon & Kevin J. McGraw. 2013. Chameleons communicate with complex colour changes during contests: different body regions convey different information. Biol. Lett., vol. 9, no. 6; doi: 10.1098/rsbl.2013.0892