Thermal and fitness-related consequences of nest location in Painted Turtles (Chrysemys picta)

1. Laboratory experiments have documented substantial temperature effects o n the physiological ecology of reptilian eggs, embryos and offspring. Howev er, functional links between important habitat characteristics, nest microe nvironments and fitness-related traits of neonates in natural nests have ra rely been studied. 2. A field study of 11 Painted Turtle (Chrysemys picta) nests was conducted to quantify the relationships between a habitat characteristic (i,e. veget ational cover around nests at oviposition) and (1) developmental temperatur e and its effect on offspring sex ratio and (2) hibernation temperature and its effect on offspring survivorship. 3. Vegetational cover was negatively correlated with nest temperatures in J uly, the period when offspring sex is determined. However, neither vegetati onal cover nor mean nest temperature predicted nest sex ratios, although co rrelations among these variables were consistent with causal relationships derived from laboratory studies. 4, Summer vegetational cover was also negatively correlated with measures o f winter nest temperatures. Of the three nests exhibiting overwinter mortal ity, two were surrounded by thick vegetation and all experienced temperatur es below - 8 degrees C, The remaining nests reached temperatures as low as - 6 degrees C without mortality, indicating that hatchlings in these nests exhibited remarkable supercooling ability. 5. The results suggest that habitat characteristics and nest microenvironme nts are functionally linked and have fitness consequences for both embryos and offspring, implying that nest-site choice by female turtles could have considerable utility.