January 30, 2008

Chameleons Change Color For Various Reasons

A recent study led by Dr. Devi Stuart-Fox of the University of Melbourne, Australia, reveals that the color-changing ability of chameleons was first used to make them more noticeable. This is contrary to previous beliefs that they changed color for camouflage, only to help them blend in with their surroundings.

Chameleons change colors frequently for various reasons: to control their temperature, for camofoulage and to communicate. Until recently it was unclear why chameleons would occasionally flash bright colors.

Dr. Stuart-Fox's team of researchers studied 21 species of southern African dwarf chameleon to compare their evolutionary relationships and ability to change color. The eye of the Chameleon can not only sense what humans can, but its eyes have the ability to see Ultraviolet color as well.

The research team measured the color changes with a spectrometer, a tool that measures the visual color range as well as UV. They used their findings in combination with information on the visual system of chameleons to try to determine what the chameleons saw.

What the researchers found was that their color-changing abilities allowed them to signal other chameleons in an appropriate manner for different situations. They pitted chameleons against each other to watch the color range between dominant and submissive colors.

Dr. Stuart-Fox said of the findings, "If a male is challenged by another male they both begin by showing their brightest colors - until one figures out the other is going to win and changes to a submissive, dark, 'don't beat me up color'."

Besides viewing chameleons' response to other chameleons, they also measured their response to predators, such as a model snake or bird. The most dramatic color changes were used to signal other chameleons, not, as previously thought, to camouflage themselves to predators. The variety in the colors had nothing to do with the range of background colors in the chameleons' habitats; it simply depended on how conspicuous they were to other chameleons.

The research concluded that chameleons evolved their color change for signaling. According to Dr. Stuart-Fox that signaling was meant "to fend off rivals or attract a mate"¦not so they could match a greater variety of backgrounds."


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University of Melbourne, Australia