Hatchlings of the North American painted turtle (Chrysemys picta) typically
spend their first winter of life inside the shallow, subterranean nest whe
re they completed incubation the preceding summer. This facet of their natu
ral history commonly causes neonates in northerly populations to be exposed
in mid-winter to ice and cold, which many animals survive by remaining unf
rozen and supercooled. We measured the limit of supercooling in samples of
turtles taken shortly after hatching and in other samples after 2 months of
acclimation (or acclimatization) to a reduced temperature in the laborator
y or field. Animals initially had only a limited capacity for supercooling,
but they acquired an ability to undergo deeper supercooling during the cou
rse of acclimation. The gut of most turtles was packed with particles of so
il and eggshell shortly after hatching, but not after acclimation. Thus, th
e relatively high limit of supercooling for turtles in the days immediately
after hatching may have resulted from the ingestion of soil land associate
d nucleating agents) by the animals as they were freeing themselves from th
eir eggshell, whereas the relatively low limit of supercooling attained by
acclimated turtles may have resulted from their purging their gut of its co
ntents. Parallels mag, therefore, exist between the natural-history strateg
y expressed by hatchling painted turtles and that expressed by numerous ter
restrial arthropods that withstand the cold of winter by sustaining a state
of supercooling.