Predator–prey interactions between crayfish (<i>Orconectes juvenilis</i>) and snails (<i>Physa gyrina</i>) are affected by spatial scale and chemical cues

Abstract

Abstract. We conducted two experiments to compare the behaviors of predatory crayfish ( Orconectes juvenilis ) and snail prey ( Physa gyrina ), with and without exposure to injured‐snail cues, in seven different sizes of arena. Individuals in both O. juvenilis and P. gyrina are known to obtain information about predation events from chemical cues present in the water, but the effect of spatial scale on this information or the ensuing interaction has not been previously investigated. We found that crayfish were generally more active in larger arenas, but their response to injured‐snail cues decreased as arena size increased. Snails responded to injured‐snail cue by seeking refuge, but responded less strongly in larger arenas. Less time was required for crayfish to capture a snail in the presence of injured‐snail cue, and there was an interaction between cue and arena size evident in middle‐sized arenas. Consumption time was lower in the presence of injured‐snail cue but was unaffected by arena size. Based on these results, we conclude that the effects of injured‐snail cue are mediated by spatial scale, and this affects the outcome of this predator–prey interaction. Spatial scale should be considered in the design and interpretation of other predator–prey studies, particularly when sensory or motility differences exist between predators and prey that affect how each gathers information about the environment.