Sex differences in alternative reproductive tactics in response to predation risk in tree crickets

Alternative reproductive tactics (ARTs) are variable, often discontinuous, behaviours that allow a particular sex to achieve enhanced mating success. Predation risk has been hypothesised to drive the evolution of ARTs, but few empirical studies have examined this. It is unclear whether predators affect fitness of the two sexes directly, by reducing survival, or indirectly, by altering mate searching. In crickets, mate search typically involves acoustic signalling by males and acoustic‐mediated movement towards males by silent females. Males and females may however employ ARTs, which includes silent searching by males, and mating without performing phonotaxis in females. We empirically examined effects of increased predation risk on mate searching behaviour and survival of male and female tree crickets, and their effects on mating success, using field‐enclosure experiments with tree crickets Oecanthus henryi and their primary predator, green lynx spiders Peucetia viridans . Crickets were allocated into three treatments with different levels of predation risk. Increased predation risk strongly reduced survival, and thereby mating success, for both sexes. With increasing predation risk, males reduced calling and increased movement towards neighbouring callers, with negative effects on mating success. By comparing with simulated random movement, we found that male movement was significantly directed towards other calling males, implying a switch to satellite strategies. Female movement behaviour, however, remained unaltered. Males and females thus differed in their response to comparable levels of predation risk, implying that the role of predation as a driver of alternative mate search strategies is sex‐specific. A free Plain Language Summary can be found within the Supporting Information of this article.