Chameleons Change Bright Colors to Communicate Aggression

Chameleons have the amazing ability to change their colors, morphing from bright green to yellow to brown. Yet these lizards change colors in unusual ways when they interact with other chameleons. Now, scientists have discovered that these color changes don't happen randomly. Instead, the lizards use these changes to convey different types of information during social interactions.

Chameleons typically have resting colors that range from brown to green, with hints of yellow. Yet each chameleon has unique markings that are specific to them. In addition, these colors change to show bright yellows, greens and turquoises during contests.

In order to take a closer look at these color changes, the researchers used photographic and mathematical modeling tools. They then examined how color shifts related to aggressive behavior. In all, the scientists studied the distance, maximum brightness and speed of color change in 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," said Russell Ligon, one of the researchers, in a news release. "In addition, head coloration--specifically brightness and speed of color change--predicted which lizard was going to win."

When chameleons 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," said Ligon in a news release. "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 contests before they even get started."

The findings reveal a bit more about chameleon behavior. The first of its kind, the study shows how new technology can allow scientists to quantify animal interactions. In addition, it's important to learn about these lizards; many chameleons are at great risk as habitat destruction occurs at alarming rates.

The findings are published in the journal Biology Letters.