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 whale）借助声呐完成猎物的探测、定位与追踪。它们会依据目标距离调整发射声强、听觉灵敏度以及回声定位点击频率，并以高重复率、低声强的蜂鸣脉冲序列终止猎物追踪。然而，此前学界普遍认为其狭窄的声学视场（field of view, FOV）在整个猎物接近阶段保持稳定，这可能会让猎物在近距离得以逃脱。本研究发现，与部分蝙蝠类似，港湾鼠海豚（harbour porpoise）在攻击终末阶段能够拓宽其生物声呐波束；但与蝙蝠不同的是，它们在该阶段内仍可调整波束宽度。结合视频、磁共振成像（magnetic resonance imaging, MRI）以及声学标签录音数据，我们提出这种波束宽度灵活性由额隆（melon）调控，其作用是适配与猎物间的动态空间关系以及周遭环境的声学复杂度。尽管鲸类与蝙蝠的演化路径相互独立，且声波产生与传播机制各不相同，但二者均能自适应调整其声学视场，这表明波束宽度灵活性是推动猎物追踪型回声定位系统演化的关键驱动因素。