Neonate ectotherms face a wide range of environmental hazards because of the diverse habitats they inhabit and their small sizes. This is especially true amongst turtles that live in temperate zones and experience winter conditions after hatching. Such hatchlings must balance challenges involving desiccation, freezing, and predation, among other threats. Four behavioral patterns are known; turtle hatchlings either overwinter in water (OIW), terrestrially overwinter shallowly in the nest and likely freeze (TIN), terrestrially overwinter deep in the nest and perhaps avoid freezing (TBN), or terrestrially overwinter outside the nest entirely and likely freeze (TON). Investigations into adaptations for cold tolerance and desiccation resistance in a suite of OIW, TIN, and TBN turtle species found that TIN and TBN species generally were able to supercool and resist freezing at lower temperatures, as well as being better at resisting desiccation.
We measured desiccation tolerance of five additional turtle species, including two that use the TON strategy (Diamondback Terrapins, Malaclemys terrapin, and Common Box Turtles, Terrapene carolina. We also tested desiccation tolerance in Blanding’s Turtles (Emys blandingii) and Northern Map Turtles (Graptemys geographica), two species whose overwintering strategy is unclear, and Wood Turtles (Glyptemys insculpta), which are probably OIW strategists.
As predicted, hatchlings of the two TON species had significantly higher resistance to desiccation than other species. In fact, Diamondback Terrapins had extraordinarily high desiccation resistance, which may be due not only to their habit of overwintering on land, but also their exposure to saline environments. Northern Map Turtles, whose overwintering strategy is mostly unknown, had relatively high desiccation resistance, about the same as that of Common Box Turtles, suggesting that Northern Map Turtles are probably either TIN or TON strategists. Blanding’s Turtles, which seem to use TON and OIW as alternate strategies, had intermediate resistance to desiccation. As predicted, the two species OIW strategists (Wood Turtles and Common Snapping Turtles), had the lowest desiccation tolerance. We therefore found additional support for the hypothesis that desiccation tolerance is associated with overwintering strategies in hatchling turtles, and found that further investigation into the overwintering strategies of Diamondback Terrapins and Northern Map Turtles would be productive