The darkness of the deep ocean limits the vision of diving predators, except when prey emit bioluminescence. It is hypothesized that deep-diving seals rely on highly developed whiskers to locate their prey. However, if and how seals use their whiskers while foraging in natural conditions remains unknown. We used animal-borne tags to show that free-ranging elephant seals use their whiskers for hydrodynamic prey sensing. Small, cheek-mounted video loggers documented seals actively protracting their whiskers in front of their mouths with rhythmic whisker movement, like terrestrial mammals exploring their environment. Seals focused their sensing effort at deep foraging depths, performing prolonged whisker protraction to detect, pursue, and capture prey. Feeding-event recorders with light sensors demonstrated that bioluminescence contributed to only about 20% of overall foraging success, confirming that whiskers play the primary role in sensing prey. Accordingly, visual prey detection complemented and enhanced prey capture. The whiskers' role highlights an evolutionary alternative to echolocation for adapting to the extreme dark of the deep ocean environment, revealing how sensory abilities shape foraging niche segregation in deep-diving mammals. Mammals typically have mobile facial whiskers, and our study reveals the significant function of whiskers in the natural foraging behavior of a marine predator. We demonstrate the importance of field-based sensory studies incorporating multimodality to better understand how multiple sensory systems are complementary in shaping the foraging success of predators.

中文翻译：

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胡须作为觅食海豹的流体动力猎物传感器。

深海的黑暗限制了潜水捕食者的视野，除非猎物发出生物发光。据推测，深潜海豹依靠高度发达的胡须来定位猎物。然而，海豹在自然条件下觅食时是否以及如何使用它们的胡须仍然未知。我们使用动物传播的标签来展示自由放养的象海豹使用它们的胡须来感知水动力猎物。安装在脸颊上的小型视频记录器记录到海豹以有节奏的胡须运动积极地将胡须伸到嘴前，就像陆地哺乳动物在探索它们的环境一样。海豹将它们的传感工作集中在深部觅食深度，通过延长胡须伸展来检测、追逐和捕捉猎物。带有光传感器的喂食事件记录器表明，生物发光仅对整个觅食成功做出了约 20% 的贡献，这证实了胡须在感知猎物方面起主要作用。因此，视觉猎物检测补充并增强了猎物捕获。胡须的作用突出了回声定位的进化替代方案，以适应深海环境的极端黑暗，揭示了感觉能力如何塑造深潜哺乳动物的觅食生态位隔离。哺乳动物通常具有可移动的面部胡须，我们的研究揭示了胡须在海洋捕食者的自然觅食行为中的重要作用。