Body size and environment influence both intraspecific and interspecific variation in daily torpor use across hummingbirds

1. Torpor, or a regulated drop in body temperature and metabolic rate, allows animals to inhabit energetically costly environments, but among torpor-using species, we have a poor understanding of how plasticity in torpor use relates to the experienced environment. 2. To better understand the ecology of daily torpor, we completed the largest study to date on the intraspecific variation of daily torpor use in hummingbirds by exposing 149 individuals of two hummingbird species to ambient or experimentally cooled temperatures in a field setting. 3. The smaller species, a latitudinal migrant, used daily torpor frequently under ambient conditions. The larger species, an elevational migrant, also used daily torpor regularly, but further increased the frequency of daily torpor use when experiencing colder temperatures and prior to migration – indicating a facultative adaptation. 4. To place our results within a broader phylogenetic context, we combined our experimental results with a m...1. 蛰伏（torpor），即受调控的体温与代谢率下降，可帮助动物占据能量成本高昂的生境，但在使用蛰伏的物种中，我们对蛰伏使用的可塑性如何与所经历的环境相关联的认知仍十分有限。 2. 为更深入地解析日常蛰伏的生态学机制，我们开展了迄今为止规模最大的蜂鸟种内日常蛰伏使用差异研究：在野外环境中，将2种蜂鸟共计149只个体暴露于常温或实验降温条件下。 3. 体型更小的物种为纬度迁徙者，在常温环境下会频繁动用日常蛰伏；体型更大的物种为海拔迁徙者，同样会规律使用日常蛰伏，且在遭遇更低温度以及迁徙前，其日常蛰伏的使用频率会进一步提升——这表明其蛰伏使用属于兼性适应策略。 4. 为将本研究结果置于更广泛的系统发育框架中进行解读，我们将实验所得数据与a m...