Nest-Site Selection: Microhabitat Variation and Its Effects on the Survival of Turtle Embryos

It is known that turtle embryos are prone to high rates of predation; however, little is known about microhabitat variation at the nest site and its effects on turtle embryo survival. Microhabitat characteristics were measured at nest sites of the striped mud turtle, Kinosternon baurii, on a sandhill in central Florida to determine whether females were choosing sites to oviposit their eggs that differed in vegetation structure from random sites. Also nests were experimentally manipulated in the field to determine whether survivorship of striped mud turtle embryos differed between nest sites and random sites. Female striped mud turtles selected sites to oviposit their eggs that differed from random. Nest sites were located closer to grass tussocks or other herbaceous vegetation and in areas of less bare ground than random sites. Soil at nonselected sites reached higher daily temperatures and maintained these higher temperatures for longer periods of time than soil at selected sites. Survivorship of embryos was higher at selected sites than at nonselected sites. Because of their small body size at sexual maturity, female striped mud turtles dig shallower nests than larger species of turtles and may need vegetative cover near the nest site to protect their embryos from thermal extremes. In these times of increased habitat destruction and alteration, it is important that we gain a more complete understanding of the quality of habitat needed for successful reproduction.