COLD TOLERANCE IN HATCHLING SLIDER TURTLES (TRACHEMYS-SCRIPTA)

The equilibrium freezing point for body fluids of hatchling slider tur tles (Trachemys scripta) is approximately -0.6 C, but turtles in dry, ice-free environments supercool quite readily at least to -4 C. Howeve r, the integument of neonatal sliders offers little resistance to the penetration of ice into body compartments from the environment, and fr eezing of body fluids usually is fatal. Thus, hatchling that survive o ver winter in the field probably are in subterranean hibernacula where surrounding soil remains unfrozen. The northern limit of distribution for sliders consequently may be set by the depth to which the soil fr eezes during winter. Indeed, the limit for distribution of sliders in Illinois corresponds with a line connecting localities where the groun d freezes almost every winter to a depth of 12 cm, which is approximat ely the depth to the bottom of the average hibernaculum.