Karen M. Warkentin (PI) and J. Gregory McDaniel (co-PI) Eggs often suffer high levels of predation, but were thought to be incapable of defending themselves. The recent discovery of amphibian embryos that hatch early to escape predators changed this view, and evidence for similar responses in fishes and spiders suggests that many embryos may respond adaptively to changing risks. In any life stage, appropriate responses to threat depend on the acquisition and processing of information. This study investigates the sensory world and behavioral decisions of embryos, using the best-studied case of embryonic anti-predator responses. The arboreal embryos of red-eyed treefrogs use vibrations in the egg mass to detect predatory snakes and wasps, and distinguish them from benign disturbances such as wind and rain. Many other animals, from insects to mammals, use vibrations in communication and/or predator-prey interactions, but research has been limited by technical difficulties in reproducing these vibrations. This interdisciplinary research will develop new methods for the analysis and reproduction of biologically relevant vibrations, and then apply them to ask how red-eyed treefrog embryos use vibrations to decide when to hatch. To characterize the sensory environment of embryos, vibrations caused by important dangerous and benign natural disturbances, and standardized artificial disturbances, will be recorded. These recordings will be analyzed to determine which characteristics of the vibrations carry information that embryos could use to assess risk, and to inform the design of experimental stimuli. To determine which characteristics of vibrations embryos actually use to assess danger, a mechanical shaker will be used to expose embryos to standardized sets of vibrational stimuli. This study will elucidate the rich sensory world and information processing abilities of embryos, and improve our knowledge of how animals use vibrational information. It will facilitate the flow of information between behavioral biology and mechanical engineering, thus advancing bio-vibrations research, and provide students with a unique opportunity to participate in this cross-disciplinary endeavor.
