Data from: Range-dependent flexibility in the acoustic field of view of echolocating porpoises (Phocoena phocoena)

Toothed whales use sonar to detect, locate, and track prey. They adjust emitted sound intensity, auditory sensitivity and click rate to target range, and terminate prey pursuits with high-repetition-rate, low-intensity buzzes. However, their narrow acoustic field of view (FOV) is considered stable throughout target approach, which could facilitate prey escape at close-range. Here, we show that, like some bats, harbour porpoises can broaden their biosonar beam during the terminal phase of attack but, unlike bats, maintain the ability to change beamwidth within this phase. Based on video, MRI, and acoustic-tag recordings, we propose this flexibility is modulated by the melon and implemented to accommodate dynamic spatial relationships with prey and acoustic complexity of surroundings. Despite independent evolution and different means of sound generation and transmission, whales and bats adaptively change their FOV, suggesting that beamwidth flexibility has been an important driver in the evolution of echolocation for prey tracking.

齿鲸（Toothed whales）会利用声呐（Sonar）开展猎物的探测、定位与追踪工作。它们可根据目标距离调整发射声强、听觉敏感性以及咔哒率，并以高重复率、低强度的终末嗡鸣信号终止对猎物的追踪。然而，此前学界普遍认为，其狭窄的声学视场（Acoustic Field of View，FOV）在整个接近目标的过程中保持稳定，这一特性可能会为猎物在近距离逃脱提供便利。本研究发现，与部分蝙蝠类似，港湾鼠海豚可在攻击的终端阶段拓宽其生物声呐波束；但与蝙蝠不同的是，它们仍可在该阶段内调整波束宽度。基于视频、磁共振成像（Magnetic Resonance Imaging，MRI）以及声学标记录音的实验数据，我们提出这种波束灵活性由额隆（melon）调控，其功能是适配与猎物间的动态空间关系以及周围环境的声学复杂性。尽管鲸类与蝙蝠的演化路径相互独立，且声波产生与传播的机制各不相同，但二者均会自适应地调整其声学视场（FOV），这表明波束宽度灵活性是驱动猎物追踪回声定位系统演化的关键因素之一。