for National Geographic News
Chameleons evolved their famous skin-altering abilities not for camouflage but to communicate quickly with others, a new study suggests.
Scientists have known that the reptiles use color-changing for a variety of purposes: to blend in to the environment, to regulate their body heat, and to send messages to other chameleons.
Instead of vocalizing or using pheromones, chameleons communicate visually by changing the colors and patterns of their skin. Different colors and patterns mean different things—similar to how the colors of a traffic light direct drivers.
For example, the brighter colors a male displays, the more dominant he is. So male chameleons can attract a mate or defend their territory by flashing bright colors to each other. To communicate submission or surrender, a male will display drab browns and grays.
Females also use a colorful version of signaling to communicate when they want to reject mates or are pregnant.
But how these traits evolved remained a mystery—until now.
Devi Stuart-Fox, a zoologist at the University of Melbourne in Australia, and her colleague Adnan Moussalli, a biologist at University of KwaZulu Natal in South Africa, ran experiments on 21 species of southern African dwarf chameleons to figure out why these color-changing abilities formed.
(See a photo gallery of colorful chameleons.)
If camouflage drove the evolution of color change, the species of chameleon that display the greatest diversity of skin coloration would have the greatest variety of backgrounds to match their habitats.
One hypothesis is social communication primarily drove the evolution of color change. In that scenario species that possessed the widest range of color change would have the flashiest displays.
So the scientists pitted male chameleons against each other and measured the range of their color change.
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