Semiaquatic taxa, including humans, often swim at the air–water interface where they waste energy generating surface waves. For fully marine animals however, theory predicts the most cost-efficient depth-use pattern for migrating, air-breathing species that do not feed in transit is to travel at around 2 to 3 times the depth of their body diameter, to minimize the vertical distance traveled while avoiding wave drag close to the surface. This has rarely been examined, however, due to depth measurement resolution issues at the surface. Here, we present evidence for the use of this strategy in the wild to the nearest centimeter and document the switch to shallow swimming during naturally occurring long-distance migrations. Using high-resolution depth-accelerometry and video data for little penguins ( Eudyptula minor ) and loggerhead turtles ( Caretta caretta ), satellite-relayed data for green turtles ( Chelonia mydas ), and literature data for further sea turtle, penguin, and whale species, we show that near-surface swimming is likely used broadly across nonforaging diving animals to minimize the cost of transport.

中文翻译：

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优化水平移动期间不同分类群的游泳深度


包括人类在内的半水生生物类群经常在气-水界面游泳，在那里它们浪费能量产生表面波。然而，对于完全海洋的动物，理论预测，对于迁徙的、呼吸空气的物种来说，最具成本效益的深度使用模式是在其体径深度的 2 到 3 倍左右，以尽量减少垂直传播的距离，同时避免靠近水面的波浪阻力。然而，由于表面的深度测量分辨率问题，这很少被检查。在这里，我们提供了在野外使用这种策略的证据，精确到厘米，并记录了在自然发生的长距离迁徙期间转向浅水游泳的情况。使用小企鹅 （ Eudyptula minor ） 和红海龟 （Caretta caretta） 的高分辨率深度加速度测量和视频数据，绿海龟 （ Chelonia mydas ） 的卫星中继数据，以及其他海龟、企鹅和鲸鱼物种的文献数据，我们表明近地表游泳可能广泛用于非觅食潜水动物，以最大限度地降低运输成本。