Bats enhance their call identities to solve the cocktail party problem

Echolocating bats need to solve the problem of signal jamming by conspecifics when they are in a group. However, while several mechanisms have been suggested, it remains unclear how bats avoid confusion between their own echoes and interfering sounds in a complex acoustic environment. Here, we fixed on-board microphones onto individual frequency-modulating bats flying in groups. We found that group members broaden the inter-individual differences in the terminal frequencies of pulses, thereby decreasing the similarity of pulses among individuals. To understand what features most affect similarity between pulses, we calculated the similarity of signals mimicking pulses. We found that the similarity between those artificial signals was decreased most by manipulation of terminal frequency. These results demonstrate that the signal jamming problem is solved by this simple strategy, which may be universally used by animals that use active sensing, such as echolocating bats and electric fish,...回声定位（echolocating）蝙蝠在群体活动时，需要解决同类个体产生的信号干扰问题。尽管已有多种机制被提出，但目前仍不清楚蝙蝠如何在复杂声学环境中，区分自身回声与干扰声响。本研究将机载麦克风安装于群体飞行的调频（frequency-modulating）蝙蝠个体身上。研究发现，群体中的蝙蝠会扩大个体间脉冲终端频率的差异，从而降低个体间脉冲信号的相似度。为明确哪些特征对脉冲信号相似度的影响最为显著，本研究计算了模拟脉冲信号的相似度。结果显示，通过调整终端频率可最大程度降低此类人工信号的相似度。上述结果表明，蝙蝠通过这一简单策略解决了信号干扰问题，该策略或可被依赖主动感知的动物普遍采用，例如回声定位蝙蝠与电鱼等……