Water temperature data from southern elephant seal from Marion Island with links to datasets

As the Antarctic Circumpolar Current crosses the South-West Indian Ocean Ridge, it creates an extensive eddy field characterised by high sea level anomaly variability. We investigated the diving behaviour of female southern elephant seals from Marion Island during their post-moult migrations in relation to this eddy field in order to determine its role in the animals' at-sea dispersal. Most seals dived within the region significantly more often than predicted by chance, and these dives were generally shallower and shorter than dives outside the eddy field. Mixed effects models estimated reductions of 44.33 ± 3.00 m (maximum depth) and 6.37 ± 0.10 min (dive duration) as a result of diving within the region, along with low between-seal variability (maximum depth: 5.5 % and dive duration: 8.4 %). U-shaped dives increased in frequency inside the eddy field, whereas W-shaped dives with multiple vertical movements decreased. Results suggest that Marion Island's adult female elephant seals' dives are characterised by lowered cost-of-transport when they encounter the eddy field during the start and end of their post-moult migrations. This might result from changes in buoyancy associated with varying body condition upon leaving and returning to the island. Our results do not suggest that the eddy field is a vital foraging ground for Marion Island's southern elephant seals. However, because seals preferentially travel through this area and likely forage opportunistically while minimising transport costs, we hypothesise that climate-mediated changes in the nature or position of this region may alter the seals' at-sea dispersal patterns.

当南极绕极流（Antarctic Circumpolar Current）穿过西南印度洋海脊（South-West Indian Ocean Ridge）时，会形成一片范围广阔的涡旋场（eddy field），其特征为显著的海平面异常（sea level anomaly）变异性。本研究针对马里恩岛（Marion Island）的雌性南象海豹（southern elephant seals），在其换毛后洄游（post-moult migrations）期间的潜水行为（diving behaviour）与该涡旋场的关联展开调查，以明确涡旋场对该物种远洋扩散模式的作用。
多数海豹在该区域内的潜水频次显著高于随机预期，且此类潜水的深度与时长普遍低于涡旋场外的潜水。混合效应模型（mixed effects models）估算显示，在该区域内潜水会使最大深度降低44.33±3.00米，潜水时长减少6.37±0.10分钟，同时海豹个体间的差异较低（最大深度差异为5.5%，潜水时长差异为8.4%）。
涡旋场内U型潜水（U-shaped dives）的发生频次上升，而带有多次垂直运动的W型潜水（W-shaped dives）则有所减少。研究结果表明，马里恩岛的成年雌性南象海豹在换毛后洄游的起始与返程阶段遭遇涡旋场时，其潜水的运输成本（cost-of-transport）有所降低。这一现象可能源于海豹离岛与返岛时身体状况变化所带来的浮力（buoyancy）改变。
本研究结果并未表明该涡旋场是马里恩岛南象海豹的关键觅食场所。然而，由于海豹会优先选择该区域作为途经路径，并可能在最小化运输成本的同时进行机会性觅食，我们提出假说：气候介导的该区域性质或位置变化，可能会改变海豹的远洋扩散模式。