Is the Podarcis muralis lizard left-eye lateralised when exploring a new environment?

Abstract

The typical lateral eye position in ectotherms likely facilitated the spread of visual lateralisation—i.e., the different use of the eyes—in those species. The diffusion of this form of lateralisation seems due to the possibility of carrying out more than one task simultaneously, some controlled by one eye and the visual structures it feeds and some by the other. Similar to other species, exploratory and monitoring behaviours seem to be under left “eye system” control. Wild individuals of the Common wall lizard Podarcis muralis were tested individually in captivity to ascertain whether they showed lateralisation when exploring a new environment, using preferentially the left eye. In Experiment 1, the lizards explored a maze. A left-turning bias was found, both at individual and population level, indicating a possible right hemisphere visual control. In Experiment 2, lizards explored a T-maze, preferring to enter the left rather than the right arm though without any particular preference in the head turns. In Experiment 3, the lizards had to exit an opaque box within a terrarium. We found a left-eye preference again for head turn while leaving the box. Our findings support the hypothesis of right hemisphere mediation of exploratory and monitoring behaviours in Podarcis muralis. In addition to previous studies on the same species, our results support the hypothesis of a simultaneous control of anti-predatory and exploratory behaviours (left-eye mediated) and predatory behaviour (right-eye mediated).

Keywords:

• Common wall lizard
• Exploration
• Control
• Podarcis muralis
• Visual laterality

Acknowledgements

We thank both the Parma Provincial Administration for the authorisation to capture lizards and the “El Ventorrillo” MNCN Field Station for use of their facilities. We also are grateful to Marco Mazzoni for his help in data collection, to Richard Andrew and the Proof Reading Service for their valuable comments and English revision to an earlier draft. This study was supported by the European Community (1st Programme Structuring the European Research Area, under SYNTHESYS, at the Museo Nacional de Ciencias Naturales [CSIC]), by the Spanish Ministerio de Ciencia e Innovación project MCI-CGL2008-02119/BOS, by the Italian Ministero dell'Istruzione, Università e Ricerca, and by doctoral grants from the University of Parma to BB.