Lateralization in the escape behaviour of the common wall lizard (Podarcis muralis)

Lateralization in ectotherms is now as well studied as in endotherms. Bias in eye use seems widespread, particularly in several ectotherms, most of them having lateral eyes. Several studies evidenced that the right eye/left hemisphere is involved in predatory behaviour and food searching while the left eye/right hemisphere seems to control predator monitoring, making lateralized individuals able to carry out both tasks simultaneously. Starting from previous observations that demonstrated a right-eye/left-hemisphere preference for observing a prey in common wall lizards, Podarcis muralis, we investigated whether a visual lateralization in antipredatory behaviour is present too. In a first experiment, we induced lizards in a terrarium to escape from a simulated predator attacking from behind, recording the direction of the escape path in relation to the starting point. We found that the preferred escape direction of most lateralized individuals was to the right and there was also a strong rightward preference in escape direction as a whole. In a second experiment the lizards, again stimulated from behind, had to choose to run down either the right or the left arm of a semi-circular tunnel ("ram-horn" maze). The rightward preference in escape behaviour was confirmed in this experiment too. We conclude that the constant rightward escape could be due to a left-eye early perception of the threatening cue and to the possibility it gives of better monitoring of most of the terrarium surface. Moreover, we found a left bias in turning the head for monitoring the predatory stimulus during escape, supporting the hypothesis that such a preference is likely due to visual lateralization rather than to motor lateralization.