A dicey situation: capture behaviours in free-ranging dice snakes

Abstract

When captured by a predator, the prey’s options for escape decrease dramatically; however, some species, such as dice snakes, display a wide variety of behaviours in order to escape. We explored how factors such as locality, body temperature, body size, sex, reproductive status (i.e. gravid vs. non-gravid), presence and state of injuries, and the presence of food affect the occurrence of behavioural displays in a capture situation within and among four free-ranging populations of dice snakes, Natrix tessellata (Colubridae). Our study shows that dice snakes regularly hiss, discharge their cloacal glands, and coat themselves in musk when captured, while other behaviours were displayed only occasionally. Our study corroborates previous findings of local differentiation in snake behaviour, especially the case of supposed Batesian mimicry in dice snakes. In three of four localities where the dice snake lives in proximity or in sympatry with nose-horned vipers, they display fake striking, with additional head flattening as opposed to the viper-free locality. Larger snakes exhibit a wider array of antipredator behaviours, which commonly include musking and hissing. Expectedly, warmer snakes were more likely to display vigorous antipredator behaviours such as struggling and striking. Injured snakes (a possible measure of a previous exposure to predation) displayed fewer behaviours and musked and hissed less. We call into question the analysis of isolated antipredator behavioural displays, and encourage using entire behavioural sequences in order to understand the complexity of antipredator behaviour.

Significance statement

A wrong decision when facing off a predator will likely result in death, which makes predation a major sha** force behind prey behaviour. Prey animals usually try to avoid being captured as escape becomes difficult, but some species, such as dice snakes, have a large arsenal of antipredator capture behaviours at their disposal. We examined nine different capture behaviours in dice snakes across four different localities. Our study corroborates previous findings that local adaptations, injuries, sex, size, body temperature, food, and reproductive status significantly influence antipredator behaviour on capture. However, our results also suggest that the entire sequence of capture behaviours displayed might be equally important as the occurrence of each behaviour. Therefore, future studies should avoid analysis of isolated antipredator behavioural displays and instead use entire behavioural sequences to understand the complexity of antipredator behaviour.