Many tropical mammals are vulnerable to heat because their water budget limits the use of evaporative cooling for heat compensation. Further increasing temperatures and aridity might consequently exceed their thermoregulatory capacities. Here, we describe two novel modes of torpor, a response usually associated with cold or resource bottlenecks, as efficient mechanisms to counter heat. We conducted a field study on the Malagasy bat Macronycteris commersoni resting in foliage during the hot season, unprotected from environmental extremes. On warm days, the bats alternated between remarkably short micro-torpor bouts and normal resting metabolism within a few minutes. On hot days, the bats extended their torpor bouts over the hottest time of the day while tolerating body temperatures up to 42.9°C. Adaptive hyperthermia combined with lowered metabolic heat production from torpor allows higher heat storage from the environment, negates the need for evaporative cooling and thus increases heat tolerance. However, it is a high-risk response as the torpid bats cannot defend body temperature if ambient temperature increases above a critical/lethal threshold. Torpor coupled with hyperthermia and micro-torpor bouts broaden our understanding of the basic principles of thermal physiology and demonstrate how mammals can perform near their upper thermal limits in an increasingly warmer world.

中文翻译：

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热带蝙蝠通过将麻木与适应性热疗相结合来对抗热量

许多热带哺乳动物易受热影响，因为它们的水分预算限制了使用蒸发冷却来补偿热量。因此，进一步升高的温度和干旱可能会超过它们的体温调节能力。在这里，我们描述了两种新的麻木模式，一种通常与寒冷或资源瓶颈相关的反应，作为对抗热量的有效机制。我们对马达加斯加蝙蝠 Macronycteris commersoni 进行了实地研究，该蝙蝠在炎热季节在树叶中休息，不受极端环境的影响。在温暖的日子里，蝙蝠会在几分钟内在非常短的微麻木发作和正常的静息代谢之间交替。在炎热的日子里，蝙蝠会在一天中最热的时间延长它们的蛰伏期，同时耐受高达 42.9°C 的体温。适应性热疗结合降低的从麻木中产生的代谢热量允许从环境中储存更多的热量，消除对蒸发冷却的需求，从而提高耐热性。然而，这是一种高风险的反应，因为如果环境温度升高到临界/致命阈值以上，麻痹蝙蝠就无法保护体温。Torpor 加上热疗和微型 torpor 回合扩大了我们对热生理学基本原理的理解，并展示了哺乳动物如何在日益变暖的世界中接近其热上限。这是一种高风险的反应，因为如果环境温度升高到临界/致命阈值以上，麻痹蝙蝠就无法保护体温。Torpor 加上热疗和微型 torpor 回合扩大了我们对热生理学基本原理的理解，并展示了哺乳动物如何在日益变暖的世界中接近其热上限。这是一种高风险的反应，因为如果环境温度升高到临界/致命阈值以上，麻痹蝙蝠就无法保护体温。Torpor 加上热疗和微型 torpor 回合扩大了我们对热生理学基本原理的理解，并展示了哺乳动物如何在日益变暖的世界中接近其热上限。