A comparison of diel nest temperature and nest site selection for two sympatric species of freshwater turtles

Diel nest temperature profiles were recorded from natural nests of eastern mud turtles (Kinosternon subrubrum) and Florida cooters (Pseudemys floridana) to determine whether nest microhabitat selection compensates for the effect of interspecific differences in nest depth on nest temperature. Kinosternon subrubrum nest depths were significantly shallower than those of P. floridana (t = 2.93, P < 0.01). We predicted that differences in nest depth would result in K. subrubrum nest being cooler at night and warmer during daylight than the deeper P. floridana nests. Diel temperature patterns agreed with our predictions at night, but P. floridana nest temperatures were not lower than K. subrubrum nest temperatures during the day. Soil composition, slope and soil moisture were similar for the nests of both species. However, the amount of sunlight reaching the soil above K. subrubrum nest sites was substantially less than the amount above P. floridana nest sites. We suggest that these species select habitats for oviposition that differ in the amount and types of vegetative cover, which in turn affect exposure to sunlight and ultimately nest temperature.