WARKENTIN, KM; CALDWELL, MS*; MCDANIEL, JG; Boston University; Boston University; Boston University: The feeling of danger: how red-eyed treefrog embryos use vibrational cues to assess risk

Red-eyed treefrog embryos, Agalychnis callidryas develop in gelatinous egg clutches on vegetation over ponds, where they are preyed on by snakes. If attacked, embryos can hatch up to 30% earlier than they typically do if undisturbed, escaping into the water. Physical disturbance of egg clutches could indicate risk, but not all disturbances are dangerous. The most common benign disturbance, rain, differs clearly from snake attacks in temporal pattern: raindrops create shorter, more frequent disturbances than snake bites. We used a mechanical vibration playback system to examine the response of A. callidryas embryos to temporal pattern of disturbance. Recorded rainstorms and snake attacks were altered to mimic the other type of disturbance by clumping together raindrops and dividing snakebites. Playbacks of the longer duration, longer interval, snake-like pattern elicited more hatching in both cases. We also used bursts of 0-100 Hz white noise, in different temporal patterns, to map the response of embryos to duration and interval cues. Both very long duration disturbances and disturbances separated by short intervals elicited little hatching, indicating that embryos respond to specific disturbance patterns, not simply to total energy input. Matched ratios of disturbance to inter-disturbance intervals in different cycle lengths elicited different levels of hatching, as did matched cycle lengths with different proportions of vibrational disturbance to interval. This indicates that embryos attend to both the duration of disturbances and the intervals between disturbances when assessing risk. The complexity of this response suggests that predator-induced early hatching of A. callidryas embryos may involve central nervous system processing of multiple aspects of vibrational information, not simply the tuning of peripheral sensors.