Self-righting of the European pond turtle varies among populations and is related to body size, muscular strength and body condition

Abstract

Freshwater turtles, although predominantly aquatic, use the terrestrial part of their habitat for migration and egg-laying. On land, turtles are at risk of being overturned onto their carapace, which can lead to issues such as breathing difficulties, overheating, dehydration, starvation or predation. Thus, the ability to return to an upright position is essential for their survival. So far, the relationship between antipredator behaviour and self-righting has received limited investigation, and the potential effects of body condition and muscular strength have not yet been assessed in natural populations of turtles. In this study, we investigated the factors influencing locomotor performance and antipredator behaviour in the European pond turtle (Emys orbicularis) by testing 436 adult individuals in five remote populations using a self-righting test after a simulated predator attack. Smaller adults were more successful at self-righting than larger ones, and individuals with relatively greater muscle strength and better body condition self-righted more quickly. Our results reveal local adaptation in locomotor performance and antipredator behaviour. For example, turtles from heavily fished areas reacted significantly faster to a simulated predator attack than turtles from areas with little or no fishing. In addition, our results showed that females waited longer to react after a simulated predator attack and were slower to self-right successfully compared to males. These findings reveal the intricate relationship among morphology, self-righting performance and antipredator behaviour.