Department of Zoology, University of Otago, Dunedin, 9016, New Zealand; Department of Biology, Alex Ekwueme Federal University, Ndufu-Alike Ikwo, Ebonyi State, Nigeria.
Department of Zoology, University of Otago, Dunedin, 9016, New Zealand.
J Therm Biol. 2021 Apr;97:102869. doi: 10.1016/j.jtherbio.2021.102869. Epub 2021 Feb 9.
Rocky retreats are limited and geologically constrained resources for rock-dwelling nocturnal lizards. Such lizards should seek retreats that offer thermoregulatory benefits without the risk of overheating during the day, and that protect from predation. For cold-adapted species where air temperature is frequently lower than optimum temperature for performance, factors influencing retreat-site selection and whether future warmer conditions will force superficial rock slabs to be abandoned on hot days remain poorly known. Here, we predicted that retreats selected by a nocturnally foraging, cool-temperate gecko from southern New Zealand would be thermally heterogeneous and that future warmer temperature will force lizards to abandon daytime retreats on hot days. We sampled loose rock slabs (potential retreats) in a tussock-grassland site in all seasons. We measured seasonal rock temperature profiles and field body temperature (T) of captured geckos using thermography and quantified the physical characteristics of each potential retreat. We found that both physical characteristics and rock temperatures determine choice of retreats. Field T of lizards positively correlated with retreat and air temperatures. Also, retreat temperatures, including those of the substrate below the rock slabs, showed complex heterogeneity enabling lizards to choose microsites within retreats to achieve preferred body temperatures intermittently. Observed seasonal shifts in characteristics of occupied rocks imply that lizards choose retreats to maximise warmth in spring, minimise risk of overheating (remain below voluntary thermal maximum, VT) in summer and avoid freezing over winter. Our study demonstrates the importance of microclimatic conditions in influencing retreat-site selection. Climate warming might lead to seasonal changes in use of rock slabs and possibly be beneficial initially, but longer-term implications need to be examined.
岩石撤退是有限的和受地质限制的资源，为岩石居住的夜间蜥蜴。这些蜥蜴应该寻找撤退，提供热调节效益，而没有在白天过热的风险，并且免受捕食。对于适应寒冷的物种，空气温度经常低于性能的最佳温度，影响撤退地点选择的因素，以及未来温暖的条件是否会迫使在炎热的日子里放弃表面的石板，仍然知之甚少。在这里，我们预测，从新西兰南部夜间觅食的凉爽温带壁虎选择的撤退将是热异质的，未来更温暖的温度将迫使蜥蜴在炎热的日子里放弃白天的撤退。我们在所有季节都在草丛草原地区采集松散的石板（潜在的撤退）。我们使用热成像技术测量了季节性岩石温度剖面和捕获的壁虎的野外体温（T），并量化了每个潜在撤退的物理特征。我们发现，物理特征和岩石温度都决定了撤退的选择。蜥蜴的野外 T 与撤退和空气温度呈正相关。此外，撤退温度，包括石板下的基质温度，表现出复杂的异质性，使蜥蜴能够在撤退中选择微栖息地，间歇性地达到首选体温。观察到的季节性变化的特征表明，蜥蜴选择撤退，以最大限度地提高春季的温暖，尽量减少夏季过热的风险（保持在自愿热最大值 VT 以下），并避免冬季冻结。我们的研究表明，微气候条件对撤退地点选择的重要性。气候变暖可能导致石板使用的季节性变化，最初可能是有益的，但需要检查更长期的影响。
