The influence of maternal nesting behaviour on offspring survival: evidence from correlational and cross-fostering studies
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The maternal effect of nesting behaviour is important in oviparous species because choice of microhabitat (e.g. shade cover, temperature) can determine the environment in which embryos develop. In turn, this maternal choice can influence developmental trajectories and offspring phenotypes and survival. We studied maternal nesting behaviour in a western painted turtle, Chrysemys picta, population in northern Idaho, U.S.A. During 2013–2016, we examined maternal choice of nest microhabitat and used correlational data to quantify consequences on egg survival. In 2017, we conducted a cross-fostering experiment to decouple the effects of intrinsic maternal effects from extrinsic environmental factors on egg survival, while simultaneously manipulating the level of nest shade cover and distance from water using artificial nests. Females chose nest sites that were more open and warmer than randomly available habitat. Additionally, of three nesting areas, the coolest area with the most shade cover was used least by nesting females. Egg survival was associated with nest temperature in some, but not all, years. In the cross-fostering experiment, egg survival did not differ between natal and foster eggs, but was greater in maternal nests than in artificial nests. Additionally, egg survival increased with canopy openness and minimum nest temperature, especially for eggs in artificial nests. Overall, these results suggest that females select nesting conditions (warm and open nest sites) that positively affect hatching success.