Lizards Use Color To Attract Mates Even Though Such Expressions May Get Them Killed
How far would you go for love? That's the question scientists from the University of Cambridge wanted to answer in studying Aegean wall lizards (Podarcis erhardii) from the Greek islands of Skopelos and Syros. As it turned out, some male lizards are willing to risk it all, displaying vivid colorations to attract mates but that also makes them highly visible to predatory eyes.
"We wanted to get to the origins of color evolution – to find out what is causing color variation between these lizards. We wanted to know whether natural selection favors camouflage, and whether the conflicting need to have bright sexual signals might impair its effectiveness," Kate Marshall, lead author from the University of Cambridge's Department of Zoology, said in a news release.
Aegean wall lizards (Podarcis erhardii) living on the Greek islands of Skopelos and Syros were used for this study. After using models that replicated the coloration of males and females, the researchers found that male models could no longer camouflage as well and were more likely to be spotted by avian predators.
Birds see colors differently than humans, so researchers had to adjust their models to accurately replicate lizard coloration from an avian perspective. Birds are able to see ultraviolet (UV) light so it took scientists approximately 300 color variations to get it right.
"It was important to get a clay color that would be indistinguishable from a real lizard to a bird's eyes: we even tried using a paint color chart, but they all reflected too much UV. To us, the models may not look like very good likenesses, but to a bird the models should have looked the same color as the real lizards," Marshall explained.
A total of 600 clay lizards were used in the study and placed throughout ten sites on the islands. Researchers checked checked in on their clay dummies in 24-hour increments, looking for broken pieces and beak marks that indicate bird attacks.
"The fact that the birds focused their attacks on the heads of the models also shows us that they perceived them as real lizards because that is how they would attack real prey," Marshall said in a statement.
Overall they found that less camouflaged male lizard models were attacked more often than female-colored models.
"In females, selection seems to have favored better camouflage to avoid attack from avian predators. But in males, being bright and conspicuous also appears to be important even though this heightens the risk of being spotted by birds," Marshall said.
Attracting females certainly comes at a high risk – 17 perecnt of the clay males did did not survive. The 83 percent of survivers showed that some male colors may be better for camaflouge and mating.
"In past work we've found these lizards have evolved bright colors on their sides, which are more visible to other lizards on the ground than to birds hunting from above," Marshall added.
Since this study only tested the overall coloration of lizards, Marshall hopes further study will reveal how different skin patterns affect predation.
Their findings were recently published in the journal Ecology and Evolution.
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