Animals enhance sensory acquisition from a specific direction by movements of head, ears or eyes. As active sensing animals, echolocating bats also aim their directional sonar beam to selectively “illuminate” a confined volume of space, facilitating efficient information processing by reducing echo interference and clutter. Such sonar beam control is generally achieved by head movements or shape changes of the sound-emitting mouth or nose. However, lingual-echolocating Egyptian fruit bats, Rousettus aegyptiacus, which produce sound by clicking their tongue, can dramatically change beam direction at very short temporal intervals without visible morphological changes. The mechanism supporting this capability has remained a mystery. Here we measured signals from free-flying Egyptian fruit bats and discovered a systematic angular sweep of beam focus across increasing frequency. This unusual signal structure has not been observed in other animals, and cannot be explained by the conventional and widely used “piston model” that describes the emission pattern of other bat species. Through modeling we show that the observed beam features can be captured by an array of tongue-driven sound sources located along the side of the mouth, and that the sonar beam direction can be steered parsimoniously by inducing changes to the pattern of phase differences through moving tongue location. The effects are broadly similar to those found in a phased array–an engineering design widely found in human-made sonar systems that enables beam direction changes without changes in the physical transducer assembly. Our study reveals an intriguing parallel between biology and human engineering in solving problems in fundamentally similar ways.

动物通过头部，耳朵或眼睛的运动来增强从特定方向的感官获取。作为主动感应动物，回声定位的蝙蝠还瞄准其定向声纳束，以选择性地“照亮”有限的空间，从而通过减少回声干扰和混乱来促进高效的信息处理。这种声纳束控制通常通过发声的嘴或鼻子的头部运动或形状改变来实现。然而，通过用舌头回音的埃及果蝠Rousettus aegyptiacus通过单击其舌头发出声音，可以在非常短的时间间隔内显着改变波束方向，而不会可见的形态变化。支持此功能的机制仍然是个谜。在这里，我们测量了自由飞行的埃及果蝠的信号，并发现了波束聚焦在整个频率上的系统角度扫描。这种异常的信号结构尚未在其他动物中观察到，也无法用描述其他蝙蝠物种排放模式的常规且广泛使用的“活塞模型”来解释。通过建模，我们表明观察到的波束特征可以由位于嘴巴侧面的一系列舌驱动声源捕获，并且声纳波束方向可以通过移动引起的相差模式变化而同时转向舌头位置。无需更改物理换能器组件。我们的研究揭示了生物学和人类工程学在以根本上相似的方式解决问题方面的令人着迷的相似之处。