科学美国人60秒:Lizard Picks Best Color--to Stand against

Chameleons have it easy. If they need to hide from a predator they just change their appearance, and disappear against whatever they happen to be standing on. Surrounded by leaves? Turn green. Tree trunk? Brown it is.

But Aegean wall lizards have a different strategy. They live on the Greek Islands. And instead of changing their appearance, they find a safer spot. That is, they’re really good at picking out just the right background to minimize the chances that they’ll be spotted by a hungry crow or raptor.

That’s according to a new study in the journal Scientific Reports. [Kate L. A. Marshall, Kate E. Philpot, and Martin Stevens, Microhabitat choice in island lizards enhances camouflage against avian predators]

Birds can perceive both visible and ultraviolet light, so researchers snapped regular and UV photos of lizards basking on rocks to figure out how the lizards look to birds. The scientists discovered that the lizards’ camouflage is precisely tuned to avian eyeballs, helping them seem to disappear. Lizards with darker backs hang out on darker rocks. Lighter ones choose lighter rocks. It’s the first time that wild animals have been recorded explicitly choosing the best background to enhance their own camouflage.

Another observation: when lizards aren’t under the constant threat of death, they’re less picky. “On the island with the lower risk this kind of background choice, to improve their level of camouflage, is much less evident than on the island with high predation risk.”

University of Cambridge zoologist Kate Marshall, lead researcher of the study.

To pick out the right rocks, Aegean wall lizards must have an awareness of what color they are. But how do they know? “It’s a big puzzle, and I’m fascinated by the answer. Unfortunately, I don’t know the answer yet, and hopefully this study will inspire future research into it.”  

—Jason G. Goldman