Data_Sheet_1_Distribution and Habitat Suitability of Ross Seals in a Warming Ocean.docx

Understanding the determinants of poorly studied species’ spatial ecology is fundamental to understanding climate change impacts on those species and how to effectively prioritise their conservation. Ross seals (Ommatophoca rossii) are the least studied of the Antarctic pinnipeds with a limited knowledge of their spatial ecology. We present the largest tracking study for this species to date, create the first habitat models, and discuss the potential impacts of climate change on their preferred habitat and the implications for conservation. We combined newly collected satellite tracking data (2016–2019: n = 11) with previously published data (2001: n = 8) from the Weddell, King Haakon VII and Lazarev seas, Antarctica, and used 16 remotely sensed environmental variables to model Ross seal habitat suitability by means of boosted regression trees for summer and winter, respectively. Five of the top environmental predictors were relevant in both summer and winter (sea-surface temperature, distance to the ice edge, ice concentration standard deviation, mixed-layer depth, and sea-surface height anomalies). Ross seals preferred to forage in waters ranging between −1 and 2°C, where the mixed-layer depth was shallower in summer and deeper in winter, where current speeds were slower, and away from the ice edge in the open ocean. Receding ice edge and shoaling of the mixed layer induced by climate change may reduce swimming distances and diving depths, thereby reducing foraging costs. However, predicted increased current speeds and sea-surface temperatures may reduce habitat suitability in these regions. We suggest that the response of Ross seals to climate change will be regionally specific, their future success will ultimately depend on how their prey responds to regional climate effects and their own behavioural plasticity.

洞悉那些研究不足物种的空间生态学决定因素，对于理解气候变化对那些物种的影响及其有效实施保护策略至关重要。罗斯海豹（Ommatophoca rossii）是南极海豹中研究最少的一种，对其空间生态学的了解十分有限。本研究呈现了迄今为止针对该物种规模最大的追踪研究，创建了首个栖息地模型，并探讨了气候变化对其理想栖息地的潜在影响及其对保护工作的启示。本研究将2016至2019年间新收集的卫星追踪数据（n = 11）与之前公开发表的南极威德尔海、克王哈康七世海和拉扎列夫海的数据（2001年：n = 8）相结合，并利用16个遥感环境变量，通过提升回归树模型分别对夏季和冬季的罗斯海豹栖息地适宜性进行建模。在夏季和冬季，五个顶级环境预测因子均具有相关性（海面温度、距冰缘距离、冰浓度标准差、混合层深度和海面高度异常）。罗斯海豹倾向于在-1至2°C的水域觅食，夏季混合层深度较浅，冬季则较深，流速较慢，且远离开阔海洋的冰缘。由气候变化引起的冰缘退缩和混合层变浅可能会缩短游泳距离和潜水深度，从而降低觅食成本。然而，预测的流速增加和海面温度升高可能会降低这些地区的栖息地适宜性。我们认为，罗斯海豹对气候变化的响应将具有地域特异性，其未来的成功最终将取决于其猎物对区域气候影响的响应以及其自身的适应性行为灵活性。