Tuesday, 26 January 2016

Lizards camouflage themselves by choosing rocks that best match the color of their backs


Date:January 25, 2016
Source:University of Cambridge

Resting out in the open on rocks can be a risky business for Aegean wall lizards. Out in these habitats they have nowhere to hide and their backs, which show varying shades of green and brown between individuals, are dangerously exposed to birds hunting in the skies above.

New research by Kate Marshall from the University of Cambridge's Department of Zoology and Dr Martin Stevens from the University of Exeter's Centre for Ecology and Conservation, published today in Scientific Reports, shows that individual lizards are able to choose their resting spot wisely and select a rock in their natural environment that will make their backs less conspicuous to avian predators.

"This 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," says Marshall. "This is the first result of its kind in wild animals, and in lizards specifically."

"One intriguing puzzle remains: how do the lizards 'know' how camouflaged their own backs are to a bird against a particular rock?" She adds.

Other types of lizard, such as chameleons and geckos, are able to rapidly change color in a matter of seconds or minutes to better match their background environment and avoid being spotted by approaching predators. Aegean wall lizards, which are widespread across the South Balkans and many Greek islands, are unable to do this. Instead, this new research shows that they enhance their level of camouflage to hunting birds by choosing to rest on rocks that are more similar in color to that of their own backs.

Birds see the world differently from you or I: for example, they are able to see ultraviolet light whereas we cannot, which means they perceive color (and camouflage) in a very different way. Marshall and her colleagues used visual modelling to test how conspicuous individual lizards would be to a bird's eye against the backgrounds they had chosen to sit on.

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