Lateralized behavior of tortoises in front of mirrors

By investigating the laterality of the social behaviour during the mirror-images inspection, we provide the first evidence of lateralization towards social stimuli in tortoises (Testudo hermanni), a reptile that is likely to lead mostly a solitary life. The animal's position, the monocular viewing compared to the longer walls and the paw used to start a movement from resting position have been assessed. Results revealed a preference to spend significantly more time in peripheral positions, mainly in the presence of mirrors. Moreover, a consistent left-eye preference to inspect the mirror was observed (in contrast, a significant right-eye preference appeared in absence of mirrors). Lastly, a significant preference for right-paw use in starting movements has been recorded. Results suggest a crucial role of the mirror as social reinforcement in tortoises and a dominance of the right cerebral hemisphere for encoding social stimuli, a distinctive trait of many vertebrates.