Environmentally induced variation in body size and condition in hatchling snapping turtles (Chelydra serpentina)

We performed an experiment at a field site in north-central Nebraska, U.S.A., to assess the importance of the nest environment as a determinant of body size and condition in hatchling snapping turtles (Chelydra serpentina). The contents of newly constructed nests were manipulated by reciprocal transplant so that each of several nests received a complement of eggs from each of several females. The eggs were recovered from nests after 8 weeks and allowed to complete incubation under standard conditions in the laboratory. Live mass, dry mass and water content of carcasses, and dry mass of unused yolk varied significantly among hatchlings that incubated in different nests. This variation apparently resulted from variation in water exchange by eggs, because embryos in eggs that absorbed water during 8 weeks in the field consumed more of their yolk, grew to a larger size, and were better hydrated at hatching than embryos in eggs that lost water to the nest environment. Phenotypic variation of the magnitude observed in this investigation may affect survival of hatchlings, and therefore needs to be considered explicitly in theories for the evolution of life histories in these long-lived animals.