Cold-hardiness and evaporative water loss in hatchling turtles

North American turtles hatch in late summer and spend their first winter ei ther on land or underwater. Adaptations for terrestrial overwintering of ha tchlings in northern regions, where winter thermal and hydric regimes are h arsh, have not been systematically investigated in many species. We measure d intrinsic supercooling capacity, resistance to inoculative freezing, and desiccation resistance in hatchlings of terrestrial and aquatic turtles col lected from northern (Terrapene ornata, Chrysemys picta bellii, Kinosternon flavescens, Chelydra serpentina) and southern (Chrysemys picta dorsalis, T rachemys scripta, Sternotherus odoratus, Sternotherus carinatus) locales. S upercooling capacity was estimated from the crystallization temperature of turtles cooled in the absence of external ice nuclei. Mean values ranged fr om -8.1 degrees to -15.5 degreesC and tended to be lower in terrestrial hib ernators. Inoculation resistance was estimated from the crystallization tem perature of turtles cooled in a matrix of frozen soil. These values (range of means: -0.8 degrees to -13.6 degreesC) also tended to be lower in the te rrestrial hibernators, especially C. picta bellii. Mean rates of evaporativ e water loss varied markedly among the species (0.9-11.4 mg g(-1) d(-1)) an d were lowest in the terrestrial hibernators. Most species tolerated the lo ss of a modest amount of body water, although half of the sample of S. cari natus died from desiccation. In general, turtles did not regain lost body w ater from wet soil, and immersion in free water was required for rehydratio n. Therefore, desiccation resistance may be an important adaptation to terr estrial hibernation. Resistances to inoculative freezing and desiccation we re directly correlated, perhaps because they are governed by the same morph ological characteristics.