9305875 Packard Embryonic turtles survive to hatching in some nests but not in others. Moreover, hatchlings from some of the successful nests are large and robust whereas neonates from other successful nests are small and weakly. Why does survival by embryos vary? Why do hatchlings differ so much in size and vigor? Does the variation in vigor of hatchlings affect their ability to survive once they have emerged from the nest cavity? Research outlined in this proposal first will test the hypothesis that survival by embryonic turtles is affected by the physical environment in their nests (as well as by maternity). The contents of natural nests of both snapping turtles (Chelydra serpentina) and painted turtles (Chrysemys picta) will be manipulated so that effects of the environment on hatching success can be clearly distinguished from genetic and nongenetic effects related to maternity. The physical environment will be measured in these same nests so that strong inferences can be made concerning the specific causes of embryonic mortality. The program next will test the hypothesis that substantial variation in size and vigor of hatchlings is induced by the environment during incubation, and that this environmentally-induced variation affects the survival by turtles during the neonatal period. The program of study will document critical links between the environment encountered by developing embryos, survival by embryos to hatching, phenotypic variation in hatchlings, and survival by hatchlings during the neonatal period. The findings consequently will have important bearing on conservation programs that entail captive propagation and "head- starting" for several kinds of sea turtles. ***
