Knowing the Risk: Crickets Distinguish between Spider Predators of Different Size and Commonness

摘要

Predators unintentionally release chemical and other cues into their environment that can be used by prey to assess predator presence. Prey organisms can therefore perform specific antipredator behavior to reduce predalion risk, which can strongly shape the outcome of trophic interactions. In contrast to aquatic systems, studies on cue-driven antipredator behavior in terrestrial arthropods cover only few species to dale. Here, we investigated occurrence and strength of antipredator behavior of the wood cricket Nemobius sylvestris toward cues of 14 synlopic spider species that are potential predators of wood crickets. We used two different behavioral arena experiments to investigate the influence of predator cues on wood cricket mobility. We furthertested whether changes in wood cricket mobility can be explained by five predator-specific trails: hunting mode, commonness, diurnal activity, predator-prey body-size ratio, and predator-prey life stage differences. Crickets were singly recorded (1) in separate arenas, either in presence or absence of spider cues, to analyze changes in mobility on filler paper covered with cues compared with normal mobility on filter paper without cues; and (2) in subdivided arenas partly covered with spider cues, wherethe crickets could choose between cue-bearing and cue-less areas to analyze differences in residence time and mobility when crickets are able to avoid cues. Crickets either increased or reduced their mobility in the presence of spider cues. In the experiments with cues and controls in separate arenas, the magnitude of behavioral change increased significantly with increasing predator-prey body size ratio. When crickets could choose between spider cues and control, their mobility was significantly higher in the presence of cues from common spider species than from rare spiders. We therefore conclude that wood crickets distinguish between cues from different predator species and that spiders unintentionally release a species-specific composition and size-dependent quantity of cues, which lead to distinct antipredator behavior in wood crickets.