Forms of lateralisation in common wall lizards

Lateralisation, i.e. left/right differences in behaviour associated with CNS asymmetries, is widely distributed in vertebrates and shows striking correspondences in different taxa: the right eye is usually used in response to food targets, whilst left eye use is associated with complex layouts and objects. Lateral eyes species, as fishes and very often sauropsids, are good models for investigating the occurrence of lateralisation, because of minimal binocular view and the frequent minimal connections between the two cerebral hemispheres. We aimed at ascertaining the possible existence of visual lateralisation forms in the Common wall lizard (Podarcis muralis), belonging to a family (Lacertidae) neglected from that point of view. We report results obtained in several experiments carried out in different contexts: the predatory context, the anti-predatory context, and the exploratory one. When the lizards faced mealworm larvae as prey they preferred watching them with the right eye. This occurred when the lizards detected the prey at the end of either arm of a T-maze or behind a transparent barrier to detour, as well as when at the centre of a circular arena. Conversely, when the lizards escaped from a refuge after visual and sound stimulation feigning a predator, they chose to use the left eye to monitor the threatening stimulus during the escape run. The escape direction was slightly and very frequently to the right. Escaping to the right direction allowed lizards to turn the head back to the left in order to have a wider visual field with the left eye to monitor the supposed predator. Left eye use preference was ascertained even when the lizards explored a new environment, such as a maze, an open field, and an empty circular arena. We can then confirm that even in Lacertidae different tasks are monitored by different eyes and, therefore, processed by different cerebral hemispheres, maybe for the need of short- or long term memory processing.