Complementary lateralisation in the exploratory and predatory behaviour of the common wall lizard (Podarcis muralis)

Several ectotherms show lateralisation, particularly visual lateralisation. Such brain specialisation has an ancient origin and is still present in living vertebrates. One important advantage is the possibility for lateralised animals to carry out two tasks at the same time, without altering the efficiency of either one. Recent studies on the common wall lizard (Podarcis muralis) found right eye/left hemisphere bias for attention to the cues of prey, and left eye/right hemisphere bias for controlling antipredatory and exploratory behaviours. However, these studies were independent of each other and therefore were not empirical demonstrations that the directions of visual lateralisation found in this species are present in the same individual, allowing the simultaneous performance of dual tasks. In our study the same Podarcis muralis individuals carried out one exploratory and one predatory test each. We allowed each lizard to move freely in a circular arena, with opaque walls, with either nothing or mealworm larvae in the centre. In the first case the test was an exploratory test, while in the second case it was a predatory one. The results indicated that lizards preferentially used the left eye to observe the environment--i.e., during exploration--and just tended to use the right eye during predation. Hence we conclude that in the Podarcis muralis lizard lateralisation is expressed in the same individual in opposite directions, in accordance with previous observations.