Cold-hardiness and dehydration resistance of hatchling Blanding's turtles (Emydoidea blandingii):: implications for overwintering in a terrestrial habitat

The overwintering habits of hatchling Blanding's turtles, Emydoidea blandingii (Holbrook, 1838), are not well understood. To ascertain whether these turtles are well suited to hibernation on land, we examined susceptibility to dehydration, supercooling capacity, resistance to inoculative freezing, capacity for freeze tolerance, and physiological responses to somatic freezing in laboratory-reared, hatchling E. blandingii. Rates of evaporative water loss (mean +/- SE = 4.1 +/- 0.2 mg.g(-1.)d(-1)) were intermediate to rates previously reported for the hatchlings of species known to hibernate on land and in water. Supercooled hatchlings recovered from a 1-h exposure to -8 degrees or a 7-d exposure to -4degreesC. Additional turtles supercooled to -14.3 +/- 1.2degreesC (mean +/- SE) before spontaneously freezing. However, when immersed in frozen soil, their capacity to supercool was severely limited by an inability to resist inoculative freezing following contact with external ice and ice nuclei. Therefore, hatchlings likely do not use supercooling as a winter survival strategy. Hatchlings tolerated a 72-h period of somatic freezing to -3.5 degreesC and responded to somatic freezing by increasing plasma concentrations of the putative cryoprotectants lactate and glucose. Our results suggest that hatchling E. blandingii could overwinter in moist, terrestrial hibernacula where risk of dehydration is reduced and freeze tolerance is promoted.