Well known among nature’s best tricksters for their ability to change color to fit their background, chameleons have yet another talent up their lizardly sleeves – eyes that swivel around and appear to be looking in two directions at once.
Well known among nature’s best tricksters for their ability to change color to fit their background, chameleons have yet another talent up their lizardly sleeves – eyes that swivel around and appear to be looking in two directions at once.
In contrast to humans, who have to turn their heads to have a wider but still relatively narrow field of vision, chameleons enjoy a wider field of vision with the ability to swivel each of their eyes in a different direction. Called ‘voluntary strabismus,” this ability enables the chameleon to minimize its body movements to reduce the likelihood of revealing its presence to those it hunts as well as to those that might hunt them.
Is this crazy adaptation really an example of this reptile’s eyes each being independent of the other, thus enabling them to simultaneously see two different views of their world?
Chameleon computer games
To Professors Ehud Rivlin of the Technion-Israel Institute of Technology, and Prof. Gadi Katzir of the University of Haifa, this seemed like an intriguing research question. They went about answering that question by getting chameleons to play a computer game especially designed to potentially frustrate the creatures, yet possibly solve the riddle of whether chameleons really enjoy ‘eye independence.’
When the researchers showed chameleons a double image of a tiny insect moving opposite directions across a computer screen, the reptiles focused first on one image with one eye while the other eye “wandered.” Suddenly, both eyes locked on one image a nanosecond before the reptile cocked its dart-like, sticky tongue and fired at-will.
“There were a few seconds of indecision when the chameleons were deciding which target to shoot at,” said Prof. Rivlin. “If the eyes were truly independent, one would not expect one eye to stay put and then have the other eye converge. But we found that once the chameleon made its decision about which target to fire on, it swiveled the second eye around to focus on the same simulated fly the first eye was locked on.
This behavior pattern, said the researchers, suggests that the second eye has knowledge of where the first eye is directed. That the chameleons are able to track objects moving in opposite directions before deciding which one to target suggests that their eyes are not really independent, as many have believed.
Continue reading at ENN affiliate, NoCamels.
Chameleon image via Shutterstock.
