Fight or flight trade-offs and the defensive behaviour of the mountain katydid, Acripeza reticulata

The defensive repertoires of prey are shaped by diverse ecological and evolutionary demands. This can generate trade-offs between the components of defences, as in the classic 'fight or flight' dichotomy, or dedicated investment in a singular end, allowing individuals in better condition to mount a more effective defence all round. Further, sexual dimorphism may drive sex differences in such responses, although our understanding of the interaction between sexual selection and defensive behaviour is in its infancy. Deimatic, or 'startle', defences typically combine multiple protective strategies, such as camouflage and aposematism, with a rapid transition between them, and thus offer unique opportunities for studying the dynamics of suites of defensive behaviours. Here we examined the display of the sexually dimorphic mountain katydid, with the goal of identifying the factors influencing individuals' escape response and display intensity. In experimental assays designed to simulate encounters with predators, we found that sex and repeated exposure to predation attempts affected components of the defensive behaviour of individuals in diverse ways. Both short-distance (sprint) and longer-distance (endurance) speeds differed between the sexes, primarily via an interaction between the intensity of displays and exposure to repeated predation attempts. Display intensity was best explained by an interaction between experience and sex: males maintained their intensity across 3 days of repeated attacks, while females decreased it. These results reveal complex influences on the expression of antipredator behaviour, and identify potential trade-offs mediating individual responses which differ between the sexes. Our findings also highlight the need to consider sexual dimorphism and the effect of individual condition when studying complex behavioural defences.