The “right” side of sleeping: laterality in resting behaviour of Aldabra giant tortoises (Aldabrachelys gigantea)

Aldabra giant tortoises exhibit a strong preference for resting with their heads positioned on the right side during sleep-like behavior, suggesting group-level lateralization. This study, involving 67 adult tortoises (both wild and under human care), found that 42% of individuals rested with their heads to the right compared to only 21% on the left. Additionally, asymmetrical positioning of forelimbs (88%) and hindlimbs (70%) was more common than symmetrical positions. The research also revealed a relationship between the position of forelimbs and hindlimbs during rest, with no significant differences observed between wild tortoises from Curieuse Island and those in human care at Mahè Botanical Garden. These findings contribute to the understanding of brain lateralization in reptiles, particularly chelonians, and hint at possible left-eye/right-hemisphere involvement in anti-predatory responses.

Spiezio, C., Sandri, C., Joubert, F., Muzungaile, M.-M., Remy, S., Mattarelli, P., & Regaiolli, B. (2021). The “right” side of sleeping: laterality in resting behaviour of Aldabra giant tortoises (Aldabrachelys gigantea). Animal Cognition, 25(1), 195–203. https://doi.org/10.1007/s10071-021-01542-z