Chameleons have many abilities, the most famed of which is their talent to camouflage themselves by changing color. Another capability was, until now, believed to be the complete independent movement of their eyes, allowing them to view two totally separate pictures of the world. This assumption was prevalent due to the Old World lizard’s lack of cortex, resulting in very sparse intersection between the left and right sides of their brain.
Israeli researchers from the department of neurobiology in the University of Haifa, have recently discovered in laboratory experiments that a chameleon’s eyes movements are indeed co-ordinated.
“Until now, it was thought to be that chameleons and other vertebrates with lateral placed eyes cannot track two different targets at the same time, cannot divide their attention into two targets at the same time. However, we found out that they are able to simultaneously track two targets, one with each eye, which is a neural new discovery. It’s the first time that such a behavior has been documented and described, which means that the way the brain controls the eye movement is co-ordinated between the two hemispheres of the brain,” said Phd researcher Hadas Ketter-Katz, who published the study results in The Journal of Experimental Biology in July.
In laboratory tests Ketter-Katz and her team decided to use basic video games to check whether the chameleons’ left or right eyes worked independently. The chameleons were placed in front of a computer screen showing an image of a digitized insect moving from side to side, and reacted by unleashing their tongues directly at the pixilated prey.
Another game started by showing one single digitized prey at the center of the screen, meaning that the chameleon received the exact same picture in both eyes. The researchers then split the image into two insects moving to the two opposite sides of the screen. The chameleon’s eyes tracked the movement of both, one with each eye, until one target was chosen, Ketter-Katz said.
During the experiments the researchers monitored and analyzed the chameleons’ eyes movement, discovering for the first time that the lizard was capable of tracking two different targets at the same time. Ketter-Katz says they discovered that each eye had its own specific role in this process - while one eye was tracking the prey, the other tracked its own target until it converged to the first eye to lock on the target.
“We found out that each eye has a different role. We have the tracking eye that will continue tracking the target and the converging eye that will converge to the tracking eye and eventually she will choose that target. We found out that each eye has a different subtle pattern of eye movements according to her role. So even before the chameleon chose one of the targets, I could tell by the subtle patterns of the eye which one she is going to go for,” Ketter-Katz said.
She added that the research results may have wider conclusions regarding the brain structure of chameleons and similar species.
“We assume that the brain controls each eye independently with independent units of eye movements but there is a higher level of control that can co-ordinate these two. So each eye knows exactly what the other eye sees and vice versa,” Ketter-Katz said.
This newly discovered efficiency of chameleon’s eye movements may have implications for the industries of robotics and military vision technology said the researcher.
“By our results here, our documented results here, some algorithm may be written in order to switch cameras around. It can be two, three multiple cameras, ten cameras, it doesn’t matter, with a different scan pattern according to the scan pattern of the chameleons which is proved to be very efficient,” she said.