Natural hibernation sites used by bats in areas that lack cave features have long remained unresolved. To investigate hibernation site selection and winter activity of boreal bats, we recorded bat calls using passive acoustic monitoring on 16 sites. These sites included four rock outcrops with crevices and cave features, three glacial erratics or boulder fields, three ancient shores, three root cellars and three control sites where we did not expect bats to be overwintering. Our results revealed echolocation calls of Eptesicus nilssonii, Plecotus auritus and Myotis sp. We recorded significantly more activity near rock outcrops and root cellars compared to other habitats. We also found that ambient temperature had a positive effect on bat activity and found evidence that P. auritus may be using low barometric pressure as a proxy for suitable foraging conditions during the winter. Our results suggest that rock outcrops may be more important to bats than previously acknowledged, highlighting the need to take these sites in account in planning of conservation measures. Furthermore, our findings underline the suitability of using acoustic monitoring in homing on hibernation sites that are not otherwise accessible.

中文翻译：

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北方蝙蝠的冬季活动

蝙蝠在缺乏洞穴特征的地区所使用的自然冬眠场所长期以来仍未得到解决。为了调查冬蝙蝠的冬眠地点选择和冬季活动，我们使用了16个地点的被动声波监测来记录蝙蝠的鸣叫。这些地点包括四处带有缝隙和洞穴特征的岩石露头，三处冰川不稳定或巨石场，三处古老的海岸，三处根窖和三个我们不希望蝙蝠过冬的控制地点。我们的结果揭示了Eptesicus nilssonii，Plecotus auritus和Myotis的回声定位。sp。与其他栖息地相比，我们在岩石露头和地窖附近的活动明显增加。我们还发现环境温度对蝙蝠的活动有积极影响，并发现证据表明金黄色葡萄球菌可能使用低气压作为冬季合适觅食条件的替代物。我们的结果表明，岩石露头对蝙蝠的影响可能比以前承认的要重要，这突出说明了在规划保护措施时必须考虑到这些地点。此外，我们的研究结果强调了在原本无法访问的冬眠地点进行归巢时使用声学监测的适用性。