During winter hibernation, bats may become active for a variety of reasons. Such winter activity occurs at or near hibernacula, but the degree to which this activity represents long-distance travel across a wider landscape largely is unstudied. We documented patterns in landscape-wide winter activity across a west-central Indiana study site, providing some new insights into winter flight activity. We deployed acoustic recording devices in areas without any known hibernacula, each night from December through March over three consecutive winters. Twilight temperatures (1 h post-sunset) ranged from −23°C to 21°C across three winters. We recorded 4,392 call files and attributed 89% to a phonic group based on characteristic frequencies. Flight activity was recorded at all stations and during all winter months. Nightly activity mainly was a function of the temperature on that night. We recorded low-phonic bats (most likely big brown bats, Eptesicus fuscus) down to −4°C, but most activity occurred when twilight temperatures were > 0°C. Mid-phonic bat activity (most likely eastern red bats, Lasiurus borealis) occurred when temperatures were > 0°C, with most activity occurring when temperatures were > 5°C. Wind speeds > 6 m/s tended to suppress activity. The duration of inactive periods during cold spells had no effect on activity during subsequent warm nights, indicating no increasing drive for activity following long periods of inactivity. Most activity occurred within a few hours of sunset, regardless of temperature. Little pre-sunset activity was recorded in low-phonic bats, but mid-phonic bats sometimes were active in the hour before sunset. Our results suggest widespread and potentially long-distance travel by bats across our study area during warm periods, but the impetus behind this activity remains unclear.

中文翻译：

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可以预测，越冬蝙蝠在景观范围内的飞行活动会跟随美国中西部地区的温暖脉动

在冬季冬眠期间，由于各种原因，蝙蝠可能会变得活跃起来。这种冬季活动发生在冬虫夏草或冬虫夏草附近，但这种活动在更大范围内代表远距离旅行的程度尚未得到研究。我们记录了印第安纳州中西部一个研究站点的全景观冬季活动的模式，为冬季飞行活动提供了一些新见解。我们从12月至3月的每个晚上（连续三个冬天）在没有任何冬眠的地区部署了录音设备。在三个冬季中，暮光温度（日落后1小时）范围从−23°C到21°C。我们记录了4,392个呼叫文件，并根据特征频率将89％归为一个语音组。记录了所有车站和整个冬季的飞行活动。夜间活动主要是当晚温度的函数。我们录制了低声蝙蝠（很可能是大棕蝙蝠，埃特伯氏杆菌（Eptesicus fuscus）降至-4°C，但大多数活动发生在暮光温度> 0°C时。中音蝙蝠活动（最有可能的是东部红蝙蝠，Lasiurusborealis）发生在温度> 0°C时，大多数活动发生在温度> 5°C时。风速> 6 m / s倾向于抑制活动。寒假期间不活动时间的持续时间对随后的暖夜活动没有影响，表明长时间不活动后没有增加活动的动力。无论温度如何，大多数活动都在日落后的几个小时内发生。低声蝙蝠的日落前活动很少，但有时在日落前一小时活跃中声蝙蝠。我们的研究结果表明，在温暖的时期，蝙蝠在研究区域内进行了广泛且潜在的长途旅行，但这项活动的推动力尚不清楚。