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First published online January 31, 2007
Journal of Experimental Biology 210, 614-619 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001362

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Flexible information sampling in vibrational assessment of predation risk by red-eyed treefrog embryos

Karen M. Warkentin^1,2,*, Michael S. Caldwell¹, Timothy D. Siok¹, Alison T. D'Amato¹ and J. Gregory McDaniel³

¹ Department of Biology, Boston University, Boston, MA 02215, USA
² Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Panama
³ Department of Aerospace and Mechanical Engineering, Boston University, Boston, MA 02215, USA

View larger version (25K): [in this window] [in a new window]   Fig. 1. Hatching response of Agalychnis callidryas embryos to 300 s vibration playbacks eliciting similar overall levels of hatching and matched for duty cycle but differing in cycle length. (A) Hatching as a function of time; hatching was slower with longer cycles. Inset: stimuli used in playbacks, constructed from bursts of 0–100 Hz synthetic white noise. Waveforms of 12 s of the pattern of (top to bottom) 0.1:1 s, 0.25:2.5 s, 0.5:5 s, 1:10 s duration: interval times. (B) Hatching as a function of cycles of vibration. As cycle length increased, embryos sampled progressively fewer cycles before hatching. Data are means ± s.e.m. of 10 clutches per stimulus. Different letters indicate significantly different cumulative hatching curves.

View larger version (12K): [in this window] [in a new window]   Fig. 2. (A) Latency to begin hatching and (B) peak of hatching response of Agalychnis callidryas egg clutches in response to vibration playbacks differing in cycle length, plotted in terms of time (open symbols) and of cycles of vibration (closed symbols). All stimuli had a 1:10 ratio of vibration to silence, and were constructed from bursts of 0–100 Hz white noise. Data are means ± s.e.m. of 10 clutches per stimulus. For comparison, latency (s) to begin hatching in snake attacks is also plotted (N=22 attacks).

View larger version (7K): [in this window] [in a new window]   Fig. 3. A graphical model showing the hypothesized structure of the trade-off between the value of information and its cost for red-eyed treefrog eggs. Information has value (V) to the extent that it reduces potentially fatal errors about when to hatch and, for temporal properties, accrues as a diminishing function of cycles of the pattern (solid line in A). The cost of information accrues as risk of predation (R) over time (solid line in B). Elapsed time is a product of number of cycles and cycle length, thus information is more costly (A) or accrues more slowly (B) with long vs short cycles (subscripts). If embryos maximize net benefit (value minus cost) they should sample more time but fewer cycles if those cycles are long rather than short.