THERMAL ENVIRONMENT FOR OVERWINTERING HATCHLINGS OF THE PAINTED TURTLE (CHRYSEMYS-PICTA)

We monitored temperatures during the winter of 1995-1996 inside 18 nes ts containing hatchling painted turtles (Chrysemys picta). The study w as performed at the Valentine National Wildlife Refuge in north-centra l Nebraska to assess survival of neonatal turtles in relation to the t hermal environment inside their hibernacula. Minimum temperatures in t he nests varied from -3 to -21 degrees C, and were better predictors o f survival of hatchlings than other measures of the thermal environmen t. All hatchlings survived in nests where the temperature never went b elow -7 degrees C, some animals survived in nests where the minimum wa s between -7 and -13 degrees C, but no turtle survived in a nest where the minimum was below -14 degrees C. Hatchlings probably survived the cold by sustaining a state of supercooling, because the duration of e xposure to low temperatures was far too long for animals in most nests to have survived in a frozen state.