Data from: Inconspicuous echolocation in hoary bats (Lasiurus cinereus)

Echolocation allows bats to occupy diverse nocturnal niches. Bats almost always use echolocation, even when other sensory stimuli are available to guide navigation. Here, using arrays of calibrated infrared cameras and ultrasonic microphones, we demonstrate that hoary bats (Lasiurus cinereus) use previously unknown echolocation behaviors that challenge our current understanding of echolocation. We describe a novel call type (“micro” calls) that has three orders of magnitude less sound energy than other bat calls used in open habitats. We also document bats flying close to microphones (< 3 m) without producing detectable echolocation calls. Acoustic modeling indicates that bats are not producing calls that exceed 70-75 dB at 0.1 m, a level that would have little or no known use for a bat flying in the open at speeds exceeding 7 m s-1. This indicates that hoary bats sometimes fly without echolocation. We speculate that bats reduce echolocation output to avoid eavesdropping by conspecifics during the mating season. These findings might partly explain why tens of thousands of hoary bats are killed at wind turbines each year. They also challenge the long-standing assumption that bats—model organisms for sensory specialization—are reliant on sonar for nocturnal navigation.

回声定位（echolocation）使蝙蝠能够占据多样的夜行生态位。即便存在可辅助导航的其他感官刺激，蝙蝠也几乎总会使用回声定位。本研究借助经校准的红外相机阵列与超声麦克风阵列，证实银毛蝠（*Lasiurus cinereus*）存在此前未被发现的回声定位行为，这一发现挑战了我们当前对回声定位的认知。我们描述了一种全新的叫声类型——"微型"叫声，其声能较开放栖息地中其他蝙蝠的叫声低三个数量级。此外，我们记录到蝙蝠在距离麦克风不足3米的位置飞行时，并未发出可被检测到的回声定位叫声。声学建模结果显示，蝙蝠发出的叫声在0.1米处的声压级未超过70~75 dB，而对于飞行速度超过7 m s⁻¹的开放环境中飞行的蝙蝠而言，该声压级几乎不具备已知实用价值。这表明银毛蝠有时会在不使用回声定位的情况下飞行。我们推测，在交配季期间，蝙蝠会降低回声定位的发声强度，以避免被同种个体窃听。上述发现或许可以部分解释为何每年都有数以万计的银毛蝠死于风力涡轮机。同时，该研究结果也挑战了一项长期存在的既定假设：作为感官特化研究的模式生物，蝙蝠依赖声纳开展夜行导航。