Dissertation Research: Effects of Mortality Risks on an Ontogenetic Niche Shift

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9311196 Ryan This project will investigate why animals hatch when they hatch, and how the timing of hatching affects their survival. An amphibian species, Agalychnis callidryas, lays its eggs on plants overhanging ponds, and the tadpoles fall into the water when they hatch. Tadpoles are able to hatch as early as 5 days old and will do so to escape from egg-eating snakes, if they are attacked. Undisturbed tadpoles, however, usually delay hatching for several days. They continue growing, inside the egg, and when they hatch they are less vulnerable to aquatic predators than are the smaller, early-hatching tadpoles. The proposed research examines the effect on survival of developmental and behavioral flexibility in hatching, in the context of risks facing embryos and tadpoles. %%% Many animals live in different environments at different stages in their lives, and most animals hatch. The problems facing animals making such changes are general, but in many systems only one of the two stages is accessible to study under natural conditions. This study of the effects of changes in hatching time on both the eggs and larvae will add to our understanding of behavior and ecology. It will also provide detailed information on the ecology of this high profile rainforest species, particularly its interactions with its predators at a crucial life stage. *** l investigate why animals hatch when they hatch, and how the timing of hatching affects the ! ! ! ! !h h F % % ( Times New Roman Symbol & Arial # # p " h Ryan Abstract Doctoral Dissertation Elizabeth M. Behrens Elizabeth M. Behrens