Lateralization in the common wall lizard (_Podarcis muralis_)

The literature gives information about left eye/right hemisphere-mediated predatory tasks in several taxa of ectotherms, while antipredatory and exploratory behaviours are generally left eye/right hemisphere-mediated. Such a visual specialization allows individuals to hunt and maintain vigilance at the same time. Several studies show hemispherical specialization in several species of amphibians and fishes, but we do not know as much about sauropsids. In this thesis I investigate the presence of lateralization in sauropsids, in particular in the common wall lizard (Podarcis muralis), for predatory, antipredatory and exploratory behaviours. In the first experiment (A1) I found a right eye preference in observing a worm in a T-maze where lizards preferred choosing the prey placed in the left arm of the maze, a finding supported by the strong accordance between the time observation with one eye and the direction chosen being found. The right eye/left hemisphere control in prey detection was then confirmed by a detour test conducted in the second experiment (B1). Here lizards showed a preference for taking the left path in reaching prey placed behind a transparent barrier, hence again indicating a right eye preference. In contrast, in the experiment C1, on escape behaviour from a simulated predator, I found that lizards strongly preferred to escape on the right, turning back the head to the left, supporting a left eye-mediated process of antipredatory stimuli by lizards. The right path escape was then confirmed during the subsequent experiment (C2), where lizards had to run in a “ram-horn” maze, where they were obliged to choose the left or the right direction. The thesis also presents an experiment conducted in the wild that gives support to laboratory data on antipredatory behaviour. In experiment D1, a predatory attack was simulated again, starting with lizards that were basking in their natural setting. After the stimulation the lizards escaped to the nearest refuge, hence independently of any lateralization. When they emerged from the refuge, however, and they observed the exterior looking for the predator, they did so preferentially with the left eye, supporting what was found in experiment C1. In the next series of experiments, exploratory bias in a new environment was studied using a maze (experiment E1), then a T-maze again (experiment E2) and finally we observed how lizards exited a box (experiment E3). A strong left eye bias was found in carrying out these tasks. In particular, lizards showed a constant left turning pattern in the maze. This was not so evident in experiment E2, but it was supported by a left eye preference in exploring the new environment during experiment E3. Moreover, during this experiment, the lizards showed a preference for turning the head back with a left turn, similarly to what we found in experiment C1. I later conducted experiment F1, focusing on predatory and exploratory behaviours carried out by the same individual. The lizard was placed in a circular arena with or without prey at the centre. The results confirmed a strong left eye visual system bias in controlling the environment during the exploratory behaviour and, although we did not find differences in controlling the prey with a preferential eye in this task, there was a right eye bias in turning the head towards the prey when withdrawing from it. This last task is similar to what was displayed in the escape and exploratory behaviour observed in experiment C1 and experiment E3, respectively, but in this case carried out preferentially in the right (opposite) direction, as towards the prey. In conclusion, this thesis demonstrates the existence of lateralization in the common wall lizard (Podarcis muralis) showing in particular a right eye visual system control of predatory cues and a left eye visual system control of antipredatory and exploratory cues. This supports the hypothesis that the brain specialization of function could permit the performance of simultaneous important tasks.