Data from: Solar radiation during rewarming from torpor in elephant shrews: supplementation or substitution of endogenous heat production?

Many small mammals bask in the sun during rewarming from heterothermy, but the implications of this behaviour for their energy balance remain little understood. Specifically, it remains unclear whether solar radiation supplements endogenous metabolic thermogenesis (i.e., rewarming occurs through the additive effects of internally-produced and external heat), or whether solar radiation reduces the energy required to rewarm by substituting (i.e, replacing) metabolic heat production. To address this question, we examined patterns of torpor and rewarming rates in eastern rock elephant shrews (Elephantulus myurus) housed in outdoor cages with access to either natural levels of solar radiation or levels that were experimentally reduced by means of shade cloth. We also tested whether acclimation to solar radiation availability was manifested via phenotypic flexibility in basal metabolic rate (BMR), non-shivering thermogenesis (NST) capacity and/or summit metabolism (Msum). Rewarming rates varied significantly among treatments, with elephant shrews experiencing natural solar radiation levels rewarming faster than conspecifics experiencing solar radiation levels equivalent to approximately 20% or 40% of natural levels. BMR differed significantly between individuals experiencing natural levels of solar radiation and conspecifics experiencing approximately 20% of natural levels, but no between-treatment difference was evident for NST capacity or Msum. The positive relationship between solar radiation availability and rewarming rate, together with the absence of acclimation in maximum non-shivering and total heat production capacities, suggests that under the conditions of this study solar radiation supplemented rather than substituted metabolic thermogenesis as a source of heat during rewarming from heterothermy.许多小型哺乳动物在从异温状态（heterothermy）复温期间会晒太阳，但这种行为对其能量平衡的影响仍鲜为人知。具体而言，目前尚不清楚太阳辐射是会补充内源性代谢产热（即复温通过体内产热与外部热量的叠加效应实现），还是会通过替代（即取代）代谢产热来降低复温所需的能量成本。为解答这一问题，我们对饲养于室外笼舍中的东部岩象鼩（Elephantulus myurus）的蛰眠模式与复温速率展开了研究，这些笼舍要么可接触自然水平的太阳辐射，要么通过遮阳布实验性降低了太阳辐射强度。我们还测试了对太阳辐射可获得性的驯化是否会通过基础代谢率（BMR）、非颤抖产热（NST）能力以及/或最大代谢率（Msum）的表型可塑性体现出来。不同处理组的复温速率存在显著差异：接触自然水平太阳辐射的东部岩象鼩，其复温速度快于太阳辐射强度仅为自然水平约20%或40%的同种个体。接触自然水平太阳辐射的个体与太阳辐射强度约为自然水平20%的个体之间，基础代谢率存在显著差异，但非颤抖产热能力与最大代谢率在各处理组间均无明显差异。太阳辐射可获得性与复温速率之间的正相关关系，加上最大非颤抖产热与总产热能力未出现驯化现象，表明在本研究的实验条件下，太阳辐射在哺乳动物从异温状态复温的过程中，是补充而非替代代谢产热作为热量来源。