Activity times structure the thermal environments experienced by organisms. In mammals, species shift from being nocturnal to diurnal and vice versa, but the thermal consequences of variable activity patterns remain largely unexplored. Here we used theoretical thermoregulatory polygons bounded by estimates of basal metabolic rates (BMR), maximum metabolic rates (MMR), and thermal conductance (C) in small mammals to explore the metabolic consequences of exposure to global-scale daytime and nighttime temperatures. Model predictions indicated higher metabolic scope for activity for nocturnal species at low latitudes and that reduced minimum C and larger body size increased the geographic range in which nocturnality was advantageous. Consistent with predictions, within rodents nocturnal species have low C. However, nocturnal mammals tend to be smaller than diurnal species, likely reflecting the importance of additional factors driving body size. Projections of warming impacts on small mammals suggest that diurnal species could lose habitable space globally. Conversely, warming could lift cool temperature constraints on nocturnal species and increase habitable space, suggesting that a shift toward nocturnal niches might be favored in a warming world. Taken together, these findings demonstrate the importance of energetic considerations for endotherms in managing global change impacts on nocturnal and diurnal species.

中文翻译：

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哺乳动物活动时间的气候变化和温度调节后果。

活动时间构成了有机体经历的热环境。在哺乳动物中，物种从夜间活动转变为昼夜活动，反之亦然，但活动模式变化的热后果在很大程度上仍未得到探索。在这里，我们使用理论上的温度调节多边形，并以小型哺乳动物的基础代谢率（BMR），最大代谢率（MMR）和热导率（C）估计为边界，以探索暴露于全球范围内白天和夜间温度的代谢后果。模型预测表明，低纬度地区夜间物种活动的代谢范围更高，而最低碳含量降低和体型较大则增加了夜间活动性所在的地理范围。与预测一致，在啮齿类动物中，夜行性物种的C低。但是，夜间哺乳动物往往小于昼夜物种，这可能反映了驱动体型的其他因素的重要性。对小型哺乳动物变暖影响的预测表明，昼夜物种可能会在全球范围内失去可居住的空间。相反，变暖可以解除夜间物种的凉爽温度限制，并增加可居住的空间，这表明在变暖的世界中向夜间生态位的转变可能是有利的。综上所述，这些发现表明，在管理全球变化对夜间和昼夜物种的影响方面，应充分考虑吸热的重要性。气候变暖可能会解除夜间物种的凉爽温度限制，并增加可居住的空间，这表明在变暖的世界中向夜间生态位的转变可能更为有利。综上所述，这些发现表明，在管理全球变化对夜间和昼夜物种的影响方面，应充分考虑吸热的重要性。气候变暖可能会解除夜间物种的凉爽温度限制，并增加可居住的空间，这表明在变暖的世界中向夜间生态位的转变可能更为有利。综上所述，这些发现表明，在管理全球变化对夜间和昼夜物种的影响方面，应充分考虑吸热的重要性。