Abstract Insectivorous bats are particularly susceptible to heat loss due to their relatively large surface area to volume ratio. Therefore, to maintain a high normothermic body temperature, bats require large amounts of energy for thermoregulation. This can be energetically challenging for small bats during cold periods as heat loss is augmented and insect prey is reduced. To conserve energy many bats enter a state of torpor characterized by a controlled reduction of metabolism and body temperature in combination with selecting roosts based upon thermal properties. Our study aimed to quantify torpor patterns and roost preferences of free-ranging little forest bats (Vespadelus vulturnus) during winter to identify physiological and behavioral mechanisms used by this species for survival of the cold season. All bats captured were male (body mass 4.9 ± 0.7 g, n = 6) and used torpor on every day monitored, with bouts lasting up to 187.58 h (mean = 35.5 ± 36.7 h, n = 6, total number of samples [N] = 61). Torpor bout duration was significantly correlated with daily minimum and maximum ambient temperature, mean skin temperature, insect mass, and body mass of individuals and the multiday torpor bouts recorded in the cold qualify as hibernation. The lowest skin temperature recorded was 5.2°C, which corresponded to the lowest ambient temperature measurement of −5.8°C. Most bats chose tall, large, live Eucalyptus trees for roosting and to leave their roost for foraging on warmer days. Many individuals often switched roosts (every 3–5 days) and movements increased as spring approached (every 1–2 days). Our data suggest that V. vulturnus are capable of using the environmental temperature to gauge potential foraging opportunities and as a cue to reenter torpor when conditions are unsuitable. Importantly, frequent use of torpor and appropriate roost selection form key roles in the winter survival of these tiny bats.

中文翻译：

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冬季自由放养雄性小森林蝙蝠 Vespadelus vulturnus 的热生物学和栖息地选择

摘要 食虫蝙蝠由于其相对较大的表面积与体积比，特别容易受到热量损失的影响。因此，为了保持较高的正常体温，蝙蝠需要大量的能量来调节体温。这对于寒冷时期的小蝙蝠来说可能是一个巨大的挑战，因为热量损失增加了，昆虫猎物减少了。为了节省能量，许多蝙蝠进入了一种麻木状态，其特征是新陈代谢和体温的受控降低以及根据热特性选择栖息地。我们的研究旨在量化自由放养的小森林蝙蝠 (Vespadelus vulturnus) 在冬季的蛰伏模式和栖息偏好，以确定该物种在寒冷季节生存所使用的生理和行为机制。捕获的所有蝙蝠都是雄性（体重 4.9 ± 0.7 g，n = 6），每天监测时使用 torpor，持续时间长达 187.58 小时（平均值 = 35.5 ± 36.7 小时，n = 6，样本总数 [N ] = 61)。蛰伏期持续时间与每日最低和最高环境温度、平均皮肤温度、昆虫质量和个体体重显着相关，并且在寒冷中记录的多天蛰伏期被认为是冬眠。记录的最低皮肤温度为 5.2°C，对应于 -5.8°C 的最低环境温度测量值。大多数蝙蝠选择高大、活的桉树作为栖息地，并在温暖的日子离开它们的栖息地觅食。许多人经常更换栖息地（每 3-5 天），并且随着春天的临近（每 1-2 天）活动增加。我们的数据表明，V. vulturnus 能够利用环境温度来评估潜在的觅食机会，并在条件不合适时作为重新进入蛰伏期的线索。重要的是，频繁使用蛰伏和适当的栖息选择在这些小蝙蝠的冬季生存中发挥了关键作用。