P1.7 Wednesday, Jan. 4 How do tadpoles use chemical cues to assess risk? Cue concentration versus pulse frequency. WHEAT, S. K.*; CAYRON, E.; VONESH, J. R. ; WARKENTIN, K. M. ; Whitman College, Walla Walla, WA; Arizona State Univ., Phoenix; Virginia Commonwealth Univ., Richmond; Boston Univ., MA firstname.lastname@example.org
Prey often alter their phenotype in response to predator cues to reduce vulnerability at the cost of reduced growth. Thus, prey are predicted to respond proportionally to the degree of risk, but this requires they accurately assess risk in different environments. In aquatic systems, many taxa use chemical cues from predation events in risk assessment. However, questions remain regarding what aspects of these cues provide the best information about risk. Cue concentration provides information about either the number or size of prey consumed, while cue pulse frequency provides information on predation events irrespective of prey size. If pulse frequency provides less ambiguous information about risk, we might expect prey to respond more strongly to this aspect of chemical cues. We conducted two laboratory experiments with hatchlings of the red-eyed treefrog (Agalychnis callidryas) to address this question. The first experiment quantified the effects of increasing cue concentration of two predators (dragonflies and water bugs) at a common cue pulse frequency. Responses were weakly dose dependent for both predators. The second experiment quantified the effects of pulse frequency at a common total amount of cue. Increasing pulse frequency strongly reduced growth, even though individual pulses in high frequency treatments contained little cue. These results highlight the importance of cue pulse frequency in risk assessment and help us to interpret results from field experiments in which tadpoles responded more strongly to caged predators that consumed many small compared to few large prey.