ABS 2014: The Chameleon (Chamaeleo chameleon) – a Model for Non-Mammalian Patterns of Eye Movements

Here’s the first lizard talk from the Animal Behavior Society meetings! This is a guest post from Holly Brown, who studies visual and foraging ecology in herons at UConn.

Eye structure is remarkably similar among vertebrates. Therefore, one might, understandably, imagine human visual experiences to be representative of visual experiences across vertebrate taxa. However, this is not the case. Two important differences between mammalian and non-mammalian vertebrate vision are that, unlike us, the latter are able to move their eyes independently of one another, and they seem to lack stereopsis. Stereopsis is the ability to view the two independent images generated from each eye as a single image, which ought to make depth perception easier, and thus aid in important tasks such as capturing prey.

So instead of studying mammals, Gadi Katzir and his team of collaborators from the University of Haifa, Israel, are studying chameleons to better understand vertebrate vision.

Common Chameleon by Benny Trapp from Wikimedia

One of their recent experiments was aimed at finding out whether or not chameleons could simultaneously track two prey items independently with each eye, and if so, how independently (of one another) were the eyes able to move. They found that chameleons could simultaneously track different prey items with each eye, but at some point, they would always make a choice to converge both eyes onto their eventual prey target. Furthermore, they found that chameleons never struck at prey with their eyes still diverged. By pursuing this line of research, Katzir and his team may be able to glean insights as to how stereopsis may have evolved.