Abstract：
Understanding how animals meet their daily energy requirements is critical in our rapidly changing world. Small organisms with high metabolic rates can conserve stored energy when food availability is low or increase energy intake when energetic requirements are high, but how they balance this in the wild remains largely unknown. Using miniaturized heart rate transmitters, we continuously quantified energy expenditure, torpor use and foraging behaviour of free-ranging male bats (Nyctalus noctula) in spring and summer. In spring, bats used torpor extensively, characterized by lowered heart rates and consequently low energy expenditures. In contrast, in summer, bats consistently avoided torpor, even though they could have used this low-energy mode. As a consequence, daytime heart rates in summer were three times as high compared with the heart rates in spring. Daily energy use increased by 42% during summer, despite lower thermogenesis costs at higher ambient temperatures. Likely, as a consequence, bats nearly doubled their foraging duration. Overall, our results indicate that summer torpor avoidance, beneficial for sperm production and self-maintenance, comes with a high energetic cost. The ability to identify and monitor such vulnerable energetic life-history stages is particularly important to predict how species will deal with increasing temperatures and changes in their resource landscapes.
摘要：
在我们瞬息万变的世界中，了解动物如何满足其日常能源需求至关重要。高代谢率的小生物可以在食物供应不足时保存储存的能量，或者在能量需求高时增加能量摄入，但是他们如何在野外平衡这一点仍然是未知的。使用小型化的心率发射器，我们不断量化能源消耗，春季和夏季自由放养的雄性蝙蝠（Nyctalusnoctula）的使用和觅食行为。在春天,蝙蝠广泛使用托普，其特点是心率降低，因此能量消耗低。相比之下,在夏天,蝙蝠始终避免了麻木，即使他们可以使用这种低能量模式。因此,夏季的白天心率是春季心率的三倍。夏季每日能源使用量增加了42%，尽管在较高的环境温度下产热成本较低。很可能,因此，蝙蝠的觅食时间几乎增加了一倍。总的来说,我们的结果表明夏季避免托普，有利于精子的产生和自我维持，伴随着高能量成本。识别和监测这些脆弱的充满活力的生活史阶段的能力对于预测物种如何应对温度升高和资源景观变化尤为重要。
