{"id":84043,"date":"2015-08-20T21:27:46","date_gmt":"2015-08-20T18:27:46","guid":{"rendered":"https:\/\/www.technion.ac.il\/blog\/chameleon-mysteries\/"},"modified":"2015-08-20T21:27:46","modified_gmt":"2015-08-20T18:27:46","slug":"chameleon-mysteries","status":"publish","type":"post","link":"https:\/\/www.technion.ac.il\/en\/blog\/chameleon-mysteries\/","title":{"rendered":"Chameleon Mysteries"},"content":{"rendered":"

Chameleons\u2019 swivelling eyes not as independent as once thought<\/b><\/h2>\n

Chameleons\u2019 eyes track independently, but both lock-on prey for attack<\/i><\/strong><\/h4>\n
\"<\/a>
Professor Ehud Rivlin<\/figcaption><\/figure>\n

HAIFA, ISRAEL and NEW YORK (Aug. 20, 2015)<\/b> \u2013 Well known among nature\u2019s best tricksters for their ability to change color to fit their background, chameleons have yet another talent up their sleeves – eyes that swivel around and appear to be looking in two directions at once. <\/span><\/p>\n

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 their eyes each in a different direction. \u00a0Called \u2018voluntary strabismus,\u201d 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.<\/span><\/p>\n

Is this crazy adaptation really an example of this reptile\u2019s eyes each being independent of the other, thus enabling them to simultaneous see two different views of their world?<\/span><\/p>\n

To Prof. 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 \u2018eye independence.\u2019<\/span><\/p>\n

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 \u201cwandered.\u201d Suddenly, both eyes locked on one image a nanosecond before the reptile cocked its dart-like, sticky tongue and fired at-will. <\/span><\/p>\n

\u201cThere were a few seconds of indecision when the chameleons were deciding which target to shoot at,\u201d says Prof. Rivlin. \u201cIf the eyes were truly independent, one would <\/span>not<\/span> expect one eye to stay put and then have the other eye converge. \u00a0But we found that once the chameleon made its decision about which target to fire on, it swivelled the second eye around to focus on the same simulated fly the first eye was locked on.\u201d<\/span><\/p>\n

This behavior pattern, said the researchers, suggests that the second eye has knowledge of where the first eye is directed. \u00a0That the chameleons are able to track objects moving in opposite directions before deciding which one to target suggests that their eyes are not <\/span>really<\/span> independent, as many have believed. <\/span><\/p>\n

\u201cTheir eyes possibly engage in some kind of \u2018cross talk,\u2019\u201d suggested Prof. Rivlin.<\/span><\/p>\n

When chameleon eye ‘cross talk’ occurs – when the second eye locks onto the same target as the first –\u00a0this expert predator of tiny insects gets the necessary stereoscopic depth perception at just the right moment for accurate striking.<\/span><\/p>\n

Chameleons, of which there are over 200 species, are denizens of tropical climates and deserts, but widely kept as pets the world over. They have intrigued scientists and non-scientists alike with their ability to change color and skin textures and their seemingly roaming, independent-looking eyes.<\/span><\/p>\n

According to the researchers, many animals – especially fish and birds, but not mammals – have wandering, independent eyes, with each eye connected to the opposite side of the brain so that the left part of the brain knows what the right eye is doing, and vice-versa. That\u2019s more common than we realize, they said. <\/span><\/p>\n

But, no surprise, chameleons are different.<\/span><\/p>\n

\u201cWe demonstrated that when chameleons are presented with two small targets moving in opposite directions, they can perform simultaneous, smooth, monocular visual tracking,\u201d said Prof. \u00a0Rivlin. \u201cTo our knowledge, this is the first demonstration of this capacity. We suggest that in chameleons, eye movements are not simply \u2018independent,\u2019 but are disconjugate during scanning, conjugate during binocular (two-eye) tracking, and disconjugate but coordinated during monocular (one-eyed) tracking. Each eye is aware of its own location and the orientation of the other eye. It is just a different kind of cooperation that takes place in human binocular vision.\u201d<\/span><\/p>\n

The paper describing their research is published in the July 2015 issue of the <\/span>Journal of Experimental Biology<\/span><\/i><\/a> (218: 1975-1976).<\/span><\/p>\n

\n","protected":false},"excerpt":{"rendered":"

Chameleons\u2019 swivelling eyes not as independent as once thought Chameleons\u2019 eyes track independently, but both lock-on prey for attack HAIFA, ISRAEL and NEW YORK (Aug. 20, 2015) \u2013 Well known among nature\u2019s best tricksters for their ability to change color to fit their background, chameleons have yet another talent up their sleeves – eyes that… Continue Reading Chameleon Mysteries<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[24],"tags":[],"class_list":["post-84043","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"yoast_head":"\nChameleon Mysteries - \u05d4\u05d8\u05db\u05e0\u05d9\u05d5\u05df-\u05de\u05db\u05d5\u05df \u05d8\u05db\u05e0\u05d5\u05dc\u05d5\u05d2\u05d9 \u05dc\u05d9\u05e9\u05e8\u05d0\u05dc<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.technion.ac.il\/en\/blog\/chameleon-mysteries\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Chameleon Mysteries - 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