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 conspeci...

回声定位（echolocation）使蝙蝠能够占据多样的夜行生态位。蝙蝠几乎始终依赖回声定位，即便存在可用于导航的其他感官刺激。本研究借助校准红外相机与超声麦克风阵列，证实灰红蝠（Lasiurus cinereus）存在此前未被报道的回声定位行为，该行为挑战了我们当前对回声定位的认知。我们描述了一种新型叫声类型——‘微型’叫声，其声能比开阔生境中其他蝙蝠所用叫声低三个数量级。此外，我们记录到蝙蝠在距离麦克风不足3米的空域飞行时，未产生可被检测到的回声定位叫声。声学建模结果显示，蝙蝠在0.1米处发出的叫声未超过70~75分贝，这一声级对于以超过7米每秒的速度在开阔空域飞行的蝙蝠而言，几乎不存在已知的实用价值。这表明灰红蝠有时会在不使用回声定位的情况下飞行。我们推测，蝙蝠会降低回声定位的输出，以避免被同种个体窃听……