Why hatchling Blanding's turtles don't overwinter inside their nest

The equilibrium freezing point for body fluids of hatchling Blanding's turt les (Emydoidea blandingii) is near -0.7 C, but neonates that are held in a dry, ice-free environment can be (super)cooled to approximately -6 C before they begin to freeze spontaneously (i.e., by heterogeneous nucleation). Un frozen turtles recover from exposure to -4 C, so the limit of supercooling (-6 C) probably approximates their limit of cold-tolerance. When hatchlings come into contact with ice in frozen soil, however, ice crystals penetrate the integument and cause body fluids to freeze at temperatures only slight ly below the equilibrium freezing point. Freezing is fatal except at temper atures above -2.5 C. Temperatures in the soil are likely to go below -2.5 C during winter, so the risk of freezing and dying affords an explanation fo r why hatchling Blanding's turtles seldom overwinter in the natal nest.