Department of Biology, Norwegian University of Science and Technology, Trondheim NO-7491, Norway.
Nature Education, Research and Consultancy van der Kooij, Rudsteinveien 67, Slattum NO-1480, Norway.
J Exp Biol. 2023 Nov 1;226(21). doi: 10.1242/jeb.245260. Epub 2023 Nov 3.
Insectivorous bats at northern latitudes need to cope with long periods of no food for large parts of the year. Hence, bats which are resident at northern latitudes throughout the year will need to undergo a long hibernation season and a short reproductive season where foraging time is limited by extended daylight periods. Eptesicus nilssonii is the northernmost occurring bat species worldwide and hibernates locally when ambient temperatures (Ta) limit prey availability. Therefore, we investigated the energy spent maintaining normothermy at different Ta, as well as how much bats limit energy expenditure while in torpor. We found that, despite being exposed to Ta as low as 1.1°C, bats did not increase torpid metabolic rate, thus indicating that E. nilssonii can survive and hibernate at low ambient temperatures. Furthermore, we found a lower critical temperature (Tlc) of 27.8°C, which is lower than in most other vespertilionid bats, and we found no indication of any metabolic response to Ta up to 37.1°C. Interestingly, carbon dioxide production increased with increasing Ta above the Tlc, presumably caused by a release of retained CO2 in bats that remained in torpor for longer and aroused at Ta above the Tlc. Our results indicate that E. nilssonii can thermoconform at near-freezing Ta, and hence maintain longer torpor bouts with limited energy expenditure, yet also cope with high Ta when sun exposed in roosts during long summer days. These physiological traits are likely to enable the species to cope with ongoing and predicted climate change.
在高纬度地区，食虫蝙蝠需要应对一年中大部分时间没有食物的情况。因此，那些在高纬度地区全年居住的蝙蝠将需要经历一个漫长的冬眠季节和一个短暂的繁殖季节，在这个季节里，觅食时间会受到延长的日光时间的限制。伊氏菊头蝠是世界上分布最北的蝙蝠物种，当环境温度（Ta）限制猎物的可利用性时，它会在当地进行冬眠。因此，我们研究了在不同 Ta 下维持正常体温所需的能量，以及蝙蝠在进入冬眠状态时如何限制能量消耗。我们发现，尽管蝙蝠暴露在低至 1.1°C 的 Ta 下，它们并没有增加冬眠代谢率，这表明伊氏菊头蝠可以在低温环境中生存和冬眠。此外，我们发现了一个较低的临界温度（Tlc）为 27.8°C，这比大多数其他蝙蝠的临界温度低，并且我们没有发现任何对 Ta 到 37.1°C 的代谢反应的迹象。有趣的是，二氧化碳的产生随着 Tlc 以上的 Ta 的增加而增加，这可能是由于在长时间的夏季白天中，在 Tlc 以上的 Ta 下暴露在巢穴中的蝙蝠中保留的 CO2 的释放导致的。我们的研究结果表明，伊氏菊头蝠可以在接近冰点的 Ta 下进行体温调节，因此可以通过限制能量消耗来维持更长的冬眠期，同时也可以在高 Ta 下应对长时间的夏季白天。这些生理特征可能使该物种能够应对正在发生的和预测的气候变化。
