Context-dependent behavioural lateralization in the European pond turtle Emys orbicularis (Testudines, Emydidae)

Abstract

Lateralization presents clear advantages in ecological contexts since dominance of one brain side prevents the simultaneous activation of contrasting responses in organisms with laterally located eyes. This is crucial in selecting a safe refuge during a predatory attack and may strongly affect predator–prey interactions. We explored the possible presence of lateralization in the antipredatory behaviour of European pond turtles, considering their escape facing a possible predatory attack. Thirty individuals (17 males, 13 females) were exposed to three different environmental situations of gradual increasing predatory threat: escape underwater from an unsafe shelter, diving into the water from a basking site, righting after being overturned. All turtles were tested 20 times for each of the three experiments (60 trials per individual and 1800 overall trials). We recorded multiple behavioural responses in the general context of predation risk. This was done in order to assess both the existence of lateralization and possible correlations among different behaviours as function of lateralization. The number of significant responses to the left side was always prevalent in each of the three simulated anti-predatory situations, suggesting the existence of a lateralized behaviour in this species. At the individual level, the differences we found in the three experiments could be related to different ecological contexts and consequent risk of predation. Our findings, among the few on Chelonians, support the possible involvement of the right hemisphere activity and, most importantly, reveal how the complexity of a general predatory context can affect the laterality of escape behaviour.