Lizards Rest On Rocks that Match their Skin Color To Enhance Camouflaging

Aegean wall lizards enjoy bathing on open rocks, but finding a safe spot out of view of avian predators can be tricky. A new study from the Universities of Cambridge and Exeter suggests these lizards are able to choose their resting spot wisely and camouflage themselves with rocks that best match the color of their backs, thus ensuring they remain hidden from birds flying overhead. 

"This [study] suggests that wild individual lizards can choose to rest on the rock they will most resemble, which enhances their own degree of camouflage against visually-oriented predatory birds," Kate Marshall, one of the study researchers from the University of Cambridge's Department of Zoology, said in a news release. "This is the first result of its kind in wild animals, and in lizards specifically."

Many different lizard species - chameleons and geckos, for example - are able to change color to blend in to their background within a matter of seconds or minutes to evade an approaching predator. 

However, Aegean wall lizards, which are widespread across the South Balkans and many Greek islands, are unable to do this. That's why they must camouflage by choosing rocks that best match the color of their own backs. 

For their study, researchers tested how conspicuous individual lizards appear to predators using a visual model designed to mimic a bird's eye view. They found that each set of island individuals showed better color matching against their own chosen rock backgrounds than against other lizards' rock backgrounds. 

"This strongly suggests that lizards rest on backgrounds that heighten their own camouflage to reduce the risk of being attacked by birds, and that individual behaviors have an important role in enhancing camouflage across different microhabitats," Marshall added. "Our findings appear to be the first demonstration of this occurring in wild populations as viewed by likely predators."

Researchers also found that this defense mechanism is more apparent in female lizards, seeing as males have a conflicting need to stand out against the rocks to attract mates.

However, Marshall added one mystery still remains: How do the lizards "know" how camouflaged their own backs are to a bird against a particular rock?

Researchers suggests it may be under genetic control or that lizards simply learn from experience or their fellow comrades early in life which rocks best camouflage them from predators.

"Although we don't know what the exact mechanism is yet, we hope to uncover some clues in future research. It would also be interesting to look at whether lizards can adjust their choice of rock not just for camouflage but also to aid thermoregulation (basking site choices) and sexual signaling," Marshall concluded in the University of Cambridge's release.

Their study, recently published in the journal Scientific Reports, shows that there is much more to camouflage than just an animals appearance: Choosing the best background has a major bearing on the animal's survival. 

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