Meeting Abstract
Arboreal embryos of red-eyed treefrogs, Agalychnis callidryas, hatch prematurely to escape from egg predators, cued by vibrations in attacks. Young embryos modulate hatching based on multiple frequency and temporal properties of cues, reducing false alarms that unnecessarily expose them to risk in the water. Because the cost of false alarms decreases developmentally we hypothesize that, if sampling costs are high or stimuli ambiguous, older embryos accept more false alarms. We tested this using vibration playbacks at two developmental stages. In two experiments, we assessed changes in sensitivity to sampling costs. We designed sets of 3 stimuli, based on prior results with younger embryos, so one elicited high hatching and two elicited similarly low hatching, but sampling costs differed between low-hatching stimuli. Older embryos showed lower latency to hatch, indicating less cue sampling, and more hatching overall. Their similarly high responses to two of the stimuli suggest they ceased to discriminate using slow-to-assess properties as indicators of safety; however, they showed little hatching if either frequency spectrum or a fast temporal pattern allowed rapid assessment of low risk. In a third experiment, we controlled cycle length and information-delivery rate, but varied ambiguity, presenting temporal patterns that elicited high, medium, and low hatching of younger embryos. Older embryos again showed lower latency and more hatching, with the greatest change in response to the more ambiguous medium-hatching stimulus. Developmental changes in behavior due to ontogenetic adaptation of decision processes are likely to be widespread. Vibration-cued hatching allows us to use the power of playback experiments to improve our understanding of the development of adaptive embryo behavior.
