Thermal environments of overwintering Eastern Box Turtles (Terrapene carolina carolina)

Using a mixed-effects model for 21 Eastern Box Turtles (Terrapene carolina carolina (L., 1758)) over three winters in Maryland, USA, we demonstrate that overwintering-site temperature was mainly related to air temperature. After controlling for air temperature, between-year variation accounted for 7%, between-turtle variation accounted for 3%, and variation owing to age class accounted for 1% of the total variation in overwintering-site temperature. Turtles showed overwintering-site fidelity and the location of overwintering sites did not depend on sex or age. According to the developed function, air temperature would have to increase by 3 degrees C over the overwintering period to raise the temperature of overwintering sites by about 1 degrees C, assuming no changes in other environmental factors; this level of warming is not expected until 2070-2090 according to general climate circulation models.