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）赋予蝙蝠占据多样夜行生态位的能力。蝙蝠几乎始终依赖回声定位完成导航，即便存在其他可用于引导行进的感官刺激。本研究通过配备经过校准的红外相机阵列与超声麦克风阵列的观测系统，证实灰毛蝠（Lasiurus cinereus）存在此前未被报道的回声定位行为，该发现颠覆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"叫声，其声能仅为开阔生境中其他蝙蝠叫声的千分之一（即低三个数量级）。我们还记录到，当蝙蝠在距离麦克风不足3米的区域飞行时，并未发出可被检测到的回声定位叫声。声学建模结果显示，此类蝙蝠发出的叫声在0.1米处的声压级未超过70~75分贝；而对于在开阔生境中以超过7 m s⁻¹的速度飞行的蝙蝠而言，这一声压级几乎不具备已知的实用价值。这表明灰毛蝠有时会在不启用回声定位的情况下飞行。我们推测，在交配季，蝙蝠会降低回声定位的发声强度，以避免被同类窃听。该研究发现或可部分解释为何每年有数万只灰毛蝠死于风力涡轮机。同时，该研究也挑战了长期以来的固有认知：作为感官特化研究的模式生物，蝙蝠始终依赖声纳进行夜行导航。