Data from: Tireless travellers: Sea turtles swim continuously during long-distance movements

While rest and sleep are crucial to animals, our understanding of whether and how long-distance migrants rest has been thwarted by the inability to relay high-resolution data from multi-channel loggers via satellite. We overcame these obstacles for an iconic long-distance migrator by equipping five loggerhead sea turtles (Caretta caretta) with satellite tags and data-loggers providing depth and 3-D acceleration measurements. Turtles were translocated to open-sea locations and induced to complete oceanic migrations of tens of km to return to their nesting beach performing active, oriented movements. Across a total of >600 hours of high-resolution data, we observed (i) constant flipper frequency (ca. 0.5 Hz) indicating that turtles never ceased movement, (ii) intense subsurface swimming (mostly around 1 m) for about 50% of time and (iii) deeper, less active dives up to 80 m, which were made day and night and more frequently in offshore waters. Flipper beat amplitude was much smaller in deep dives; hence the estimated energy expenditure was 37% lower on deep dives compared to subsurface swimming. These findings suggest that turtles, which can complete migrations of >2000 km, alternate between phases of intense near-surface swimming and periods of lower activity at depth, without fully resting during migration.

尽管休息与睡眠对动物而言至关重要，但我们对长途迁徙动物是否休息、以及如何休息的认知，长期受限于无法通过卫星传输多通道记录仪采集的高分辨率数据这一难题。针对这一标志性长途迁徙物种，我们为5只红海龟（Caretta caretta）佩戴了卫星标签与可采集深度及三维加速度数据的记录仪，以此突破了上述限制。研究人员将这些红海龟转移至远海海域，并诱导它们完成数十公里的远洋迁徙以返回筑巢海滩，过程中其运动模式兼具主动性与定向性。在总计超过600小时的高分辨率数据中，我们观测到三类现象：其一，红海龟的鳍肢摆动频率恒定（约0.5Hz），表明其从未停止运动；其二，约50%的时间里，它们会在近表层水域进行高强度游动（多数深度约1米）；其三，昼夜均会进行深度更深、活跃度更低的潜水，最大深度可达80米，且在远海海域此类潜水的发生频率更高。深潜时的鳍肢摆动幅度远小于近表层游动，因此经估算，深潜过程中的能量消耗比近表层游动低37%。上述研究结果表明，能够完成2000公里以上迁徙的红海龟，会在高强度近表层游动阶段与深度低活跃度阶段之间交替进行，迁徙过程中从未完全休息。