Tolerance for Freezing in Hatchling Turtles

Hatchling painted turtles (Chrysemys picta), Blanding's turtles (Emydoidea blandingi), slider turtles (Trachemys scripta), and snapping turtles (Chelydra serpentina) were inoculated with ice at temperatures near the equilibrium freezing point for their body fluids (ca. -0.7 C) and then frozen at -2.0 C. All animals survived freezing for up to 30 h, but mortality among sliders and snapping turtles increased rapidly with longer exposures. Despite the fact that neonates of all four species are able to recover from freezing at a high subzero temperature, the adaptive strategy manifested by animals in the field is to avoid freezing altogether via attributes of morphology (painted turtles), behavior (Blanding's turtles, snapping turtles), or distribution (slider turtles). The discovery of a tolerance for freezing in hatchlings of species having diverse distributions and natural histories raises the possibility that such tolerance is a trait of general occurrence among neonatal turtles and that it is not an adaptation specifically enabling animals to withstand the rigors of winter.