FINKLER, M.S.*; STEYERMARK, A.C.; LANG, J.W.; JENKS, K.; SOTHERLAND, P.R.: Geographic variation in snapping turtle egg composition across a longitudinal transect.

Snapping turtles (Chelydra serpentina) have an extensive range across North America, inhabiting aquatic habitats in diverse thermal and hydric climates. Although geographic variation in reproductive characters such as female size, clutch size, and egg mass have been investigated, little is known about geographic variation in egg composition. In this study, we examined variation in the water content, solid content, and shell mass of snapping turtle eggs from four populations in Pennsylvania, Michigan, Minnesota, and Nebraska. Initial egg mass was similar among these four populations. Multiple regression models that included geographic location, temperature, and precipitation as predictor variables found precipitation to be the best predictor of egg composition. Shell mass was negatively correlated with precipitation whereas solid content (which trades off with water content) was positively correlated with precipitation. Thus eggs from drier geographic areas have thicker shells, less solid, and more water. These findings suggest that snapping turtle egg composition reflects hydric climate within a particular region of the species range.