Fast and furious or frozen in fear? How locomotor speed and force shape antipredator behaviour in dice snakes, Natrix tessellata (Serpentes: Natricidae)

Abstract

The antipredator behaviour of prey is assumed to be influenced by its locomotor performance. Differences in locomotor performance may influence the occurrence of different defences such as fleeing, bluffing (hissing and flattening the head) and complete immobility. To investigate this hypothesis, we measured sprint speed (escape speed from a researcher as a proxy predator) and tail pulling force (a proxy for muscular strength) of 383 dice snakes from three natural populations. We noted their antipredator response (escape, bluff or immobility) in two different situations: (i) when the snake is released and chased by a researcher, and (ii) when the snake’s tail is restrained. Relative pulling force and relative sprint speed differed among populations, with identical trends observed in absolute values of performance, pointing to local adaptations. Sprint speed had a significant association with behaviour during tests of pulling force. Slower dice snakes either try to escape or become immobile, while faster snakes display bluffing behaviour. Body size was also a significant predictor of absolute performance and antipredator behaviour. Smaller snakes prefer to flee, whereas bluffing becomes more frequent with increasing body size. Noted behaviours in the two settings were repeatable to some degree. Future studies should consider heritability of locomotor ability and antipredator behaviour in dice snakes.