Potential sources of intra-population variation in painted turtle (Chrysemys picta) hatchling overwintering strategy

Abstract

Many temperate animals spend half their lives in a non-active, overwintering state, and multiple adaptations have evolved to enable winter survival. One notable vertebrate model is Chrysemys picta, whose hatchlings display dichotomous overwintering strategies: some hatchlings spend their first winter aquatically after nest emergence in the autumn, whereas others overwinter terrestrially within their natal nest with subsequent emergence in the spring. The occurrence of these strategies varies among populations and temporally within populations; however, factors that determine the strategy employed by a nest in nature are unknown. We examined potential factors that influence intra-population variation in the overwintering strategy of C. picta hatchlings over two winters in Algonquin Park, Ontario. We found that environmental factors may be a trigger for the hatchling overwintering strategy: autumn-emerging nests were sloped towards the water and were surrounded by a relatively higher percentage of bare ground compared with spring-emerging nests. Autumnemerging hatchlings were also relatively smaller. Overwintering strategy was not associated with clutch oviposition sequence, or mammalian or avian predation attempts. Instead, autumn emergence from the nest was associated with the direct mortality threat of predation by sarcophagid fly larvae. Body condition and righting response, measured as proxies of hatchling fitness, did not differ between overwintering strategies. Costs and benefits of overwintering aquatically versus terrestrially in hatchling C. picta are largely unknown, and have the potential to affect population dynamics. Understanding winter survival has great implications for turtle ecology, thus we emphasize areas for future research on dichotomous overwintering strategies in temperate hatchling turtles.

Phenotypic plasticity of nest timing in a post‐glacial landscape: how do reptiles adapt to seasonal time constraints?

“…, Riley et al. ). Snapping turtle hatchlings cannot tolerate freezing, and fall emergence of hatchlings from the nest cavity is essential, as hatchlings overwinter in wetlands (Obbard and Brooks , Costanzo et al.…”

Molecular Physiology of Freeze Tolerance in Vertebrates

“…Across their geographic ranges, the hatchlings of various turtle species may emerge from nests in summer/autumn or delay emergence until the following spring (99,171). Delayed emergence was generally thought to protect hatchlings from predation until the spring brings warmth and plentiful food sources (99), although recent investigations suggest that a range of factors can be involved and that early or delayed emergence can vary widely from year to year even in the same population (171,208). Hatchlings that emerge early can disperse to hibernate underwater or in terrestrial sites but, at northern latitudes, those that stay in the nest over the winter require a cold hardiness strategy since nests are often only ϳ10 cm underground and frequently expose hatchlings to temperatures well below 0°C.…”

Does the oviparity-viviparity transition alter the partitioning of yolk in embryonic snakes?

“…These risks, when coupled with the lack of feeding ability in the first days or weeks of life, would result in immediate emergence being disadvantageous unless the disadvantages of remaining in the nest or mother were even higher. Delayed emergence is recognized as an adaptive trait for freshwater turtles where young individuals leaving the nest at the time of hatching might encounter inhospitable environmental conditions [ 77 – 79 ]. Unfortunately, parallel work on snakes has yet to be conducted.…”