The Overwintering Strategy of Hatchling Painted Turtles, or How to Survive in the Cold without Freezing

P turtles (Chrysemys picta) are common residents of shallow lakes and marshes across much of North America east of the Rocky Mountains—so common, in fact, that the species has become a “model organism” for studies on the ecology and evolution of chelonians (Wilbur and Morin 1988). The natural history of painted turtles differs from that of most other species in an important respect, however. Whereas neonates of other freshwater turtles usually emerge from their subterranean nest in late summer or autumn and move to a nearby marsh, lake, or stream to spend their first winter, hatchling painted turtles typically remain inside their shallow (8–14 cm) nest throughout their first winter and do not emerge above the ground until the following spring (Ernst et al. 1994). This behavior commonly causes neonatal painted turtles in northern regions—from Nebraska (Packard 1997, Packard et al. 1997a), northern Illinois (Weisrock and Janzen 1999), and New Jersey (DePari 1996) northward to the limit of distribution in southern Canada (Storey et al. 1988)—to be exposed during winter to ice and cold, with temperatures in some nests dipping below –10°C (Figure 1). Many of these hatchlings withstand such extremes and emerge from the nest when the soil finally thaws in the spring (Table 1).