Color-changing chameleons can communicate among one another by changing their appearance, according to news research from Arizona State University, which suggests that the reptiles don't just change color without a reason.

Writing in the journal Biology Letters, researchers studying veiled chameleons (Chameleon calyptratus) observed bright, intense color changes in males when challenging each other for territory or a female and increased instances of aggression in males that displayed brighter stripes. When two of the lizards are in a fight, the one with a more brightly colored head is most likely to be the victor, the researchers report.

Native to Yemen and Saudi Arabia, veiled chameleons live solitary lives, so when they approach another of their species, it is typically to contest one another, or an attempt to mate.

"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," Russell Ligon, an ASU doctoral student on the research team, said in a statement.

Ligon and his colleagues documented the brightness and speed of color change in 28 color-changing patches on the chameleons' bodies.

At rest, these veiled chameleons are typically a range of brown to green in color, but each individual has unique markings, which play a role in delivering a message when the chameleons confront one another, the researchers report, noting that during a contest the chameleons can show patches of bright oranges, yellows, greens and turquoises.

These unique markings became more accentuated when the chameleons presented their bodies sideways in the moments leading up to an altercation.

"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," 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 - five to 15 seconds. More often than not, their color displays end the contest before they even get started."

The researchers were able to use physiological data available on veiled chameleons to determine which colors they are actually able to see, and plotted that data against the range of colors documented by cameras used in their study.

University of Melbourne researcher Devi Meian Stuart-Fox, who studies chameleons but was not involved in the study, told LiveScience that the study was the first of its kind to show that the speed of color change in chameleons can affect the outcome of an altercation.

For future studies the research team hopes to study color change in other chameleon species to compare the results to the color-changing behavior in the veiled chameleons.