Lateralization of visually guided detour behaviour in the common chameleon, Chamaeleo chameleon, a reptile with highly independent eye movements.

Chameleons (Chamaeleonidae, reptilia), in common with most ectotherms, show full optic nerve decussation and sparse inter-hemispheric commissures. Chameleons are unique in their capacity for highly independent, large-amplitude eye movements. We address the question: Do common chameleons, Chamaeleo chameleon, during detour, show patterns of lateralization of motion and of eye use that differ from those shown by other ectotherms? To reach a target (prey) in passing an obstacle in a Y-maze, chameleons were required to make a left or a right detour. We analyzed the direction of detours and eye use and found that: (i) individuals differed in their preferred detour direction, (ii) eye use was lateralized at the group level, with significantly longer durations of viewing the target with the right eye, compared with the left eye, (iii) during left side, but not during right side, detours the durations of viewing the target with the right eye were significantly longer than the durations with the left eye. Thus, despite the uniqueness of chameleons' visual system, they display patterns of lateralization of motion and of eye use, typical of other ectotherms. These findings are discussed in relation to hemispheric functions.