title: Risk assessment based on indirect predation cues: revisiting fine-grained variation.
abstract: To adaptively express inducible defenses, prey must gauge risk based on indirect cues of predation. However, the information contained in indirect cues that enable prey to fine-tune their phenotypes to variation in risk is still unclear. In aquatic systems, research has focused on cue concentration as the key variable driving threat-sensitive responses to risk. However, while risk is measured as individuals killed per time, cue concentration may vary with either the number or biomass killed. Alternatively, fine-grained variation in cue, that is, frequency of cue pulses irrespective of concentration, may provide a more reliable signal of risk. Here, we present results from laboratory experiments that examine the relationship between red-eyed treefrog tadpole growth and total cue, cue per pulse, and cue pulse frequency. We also reanalyze an earlier study that examined the effect of fine-grained variation in predator cues on wood frog tadpole growth. Both studies show growth declines with increasing cue pulse frequency, even though individual pulses in high-frequency treatments contained very little cue. This result suggests that counter to earlier conclusions, tadpoles are using fine-grained variation in cue arising from the number of predation events to assess and respond to predation risk, as predicted by consumer-resource theory.
authors.affiliation: Department of Biology Virginia Commonwealth University Richmond VA ; Department of Biology East Carolina University Greenville NC.
authors.forename: Michael W
authors.initials: MW
authors.lastname: McCoy
authors.affiliation: Department of Biology Whitman College Walla Walla WA.
authors.forename: Stefan K
authors.initials: SK
authors.lastname: Wheat
authors.affiliation: Department of Biology Boston University Boston MA ; Smithsonian Tropical Research Institute Gamboa Panama.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Warkentin
authors.affiliation: Department of Biology Virginia Commonwealth University Richmond VA.
authors.forename: James R
authors.identifier: 0000-0003-2481-9988
authors.initials: JR
authors.lastname: Vonesh
keywords: Inducible defense; phenotypic plasticity; predation; tadpole