Acoustic and Functional Ecology, Max Planck Institute for Ornithology, Eberhard-Gwinner-Straße, 82319 Seewiesen, Germany.
J Acoust Soc Am. 2023 May 1;153(5):2867. doi: 10.1121/10.0019359.
Echolocation is the use of self-emitted calls to probe the surrounding environment. The atmosphere strongly absorbs sound energy, particularly high frequencies, thereby limiting the sensory range of echolocating animals. Atmospheric attenuation varies with temperature and humidity, which both vary widely in the temperate zone. Since echolocating insectivorous bats rely on ultrasound to capture insects, their foraging success might decrease with seasonal and daily variations in weather. To counteract weather-induced variations in prey detection, we hypothesised that European bats decrease call frequency and increase call energy when atmospheric attenuation increases, thereby maintaining their prey detection distance. Using acoustic localisation and automated call analysis, we measured call frequency and energy in free-flying bats of three common European insectivorous species. One species, Pipistrellus nathusii/kuhlii, increased call frequency, but simultaneously decreased call energy, while the two other species (P. pipistrellus and Myotis daubentonii) did not alter call parameters. We estimated the detection distance for prey based on the recorded call parameters and prey characteristics, using a custom-developed theoretical model. None of the three species maintained prey detection distance (it decreased by 1.7 to 3.4 m) when atmospheric attenuation increased. This study contributes to a better understanding of the sensory challenges faced by animals in fluctuating environments.
回声定位是利用自我发射的叫声来探测周围环境。大气强烈吸收声能，尤其是高频声能，从而限制了回声定位动物的感知范围。大气衰减随温度和湿度的变化而变化，而温度和湿度在温带地区变化很大。由于食虫蝙蝠依靠超声波来捕捉昆虫，因此它们的觅食成功率可能会随着天气的季节性和日常变化而降低。为了抵消猎物探测因天气而产生的变化，我们假设欧洲蝙蝠在大气衰减增加时会降低叫声频率并增加叫声能量，从而保持猎物的探测距离。我们使用声学定位和自动叫声分析，测量了三种常见的欧洲食虫蝙蝠在自由飞行中的叫声频率和能量。一种蝙蝠，皮氏蝙蝠/库氏蝙蝠，增加了叫声频率，但同时降低了叫声能量，而另外两种蝙蝠（普通伏翼和大耳无尾蝠）没有改变叫声参数。我们根据记录的叫声参数和猎物特征，使用自定义开发的理论模型，估计了猎物的探测距离。当大气衰减增加时，三种蝙蝠都没有保持猎物的探测距离（探测距离减少了 1.7 到 3.4 米）。本研究有助于更好地了解动物在波动环境中面临的感官挑战。
