(Tables 1,2) Tracking records and space use statistics of polar bears (Ursus maritimus) in Storfjorden, Svalbard@en

Arctic sea ice is declining rapidly, making it vital to understand the importance of different types of sea ice for ice-dependent species such as polar bears Ursus maritimus. In this study we used GPS telemetry (25 polar bear tracks obtained in Svalbard, Norway, during spring) and high-resolution synthetic aperture radar (SAR) sea-ice data to investigate fine-scale space use by female polar bears. Space use patterns differed according to reproductive state; females with cubs of the year (COYs) had smaller home ranges and used fast-ice areas more frequently than lone females. First-passage time (FPT) analysis revealed that females with COYs displayed significantly longer FPTs near (<10 km) glacier fronts than in other fast-ice areas; lone females also increased their FPTs in such areas, but they also frequently used drifting pack ice. These results clearly demonstrate the importance of fast-ice areas, in particular close to glacier fronts, especially for females with COYs. Access to abundant and predictable prey (ringed seal pups), energy conservation and reluctance to cross large open water areas are possible reasons for the observed patterns. However, glacier fronts are retracting in Svalbard, and declines in land-fast ice have been notable over the past decade. The eventual disappearance of these important habitats might become critical for the survival of polar bear cubs in Svalbard and other regions with similar habitat characteristics. Given the relatively small size of many fast-ice areas in Svalbard, the results observed in this study would not have been revealed using less accurate location data or lower-resolution sea-ice data.北极海冰正快速消退，明确不同类型海冰对北极熊（Ursus maritimus）这类依赖海冰物种的重要性已成为当务之急。本研究依托挪威斯瓦尔巴群岛春季采集的25条北极熊GPS遥测轨迹，结合高分辨率合成孔径雷达（SAR）海冰数据，探究雌性北极熊的精细空间利用模式。空间利用模式因繁殖状态存在显著差异：带当年幼崽的雌性北极熊（COYs）家域范围更小，且相较独居雌性，更频繁地利用固定冰区域。首次通过时间（FPT）分析结果显示，带当年幼崽的雌性北极熊在距冰川前缘<10公里的区域内，首次通过时间显著长于其他固定冰区域；独居雌性在这类区域的首次通过时间同样有所延长，但它们也会频繁使用漂流浮冰。上述结果清晰证实，固定冰区域——尤其是临近冰川前缘的固定冰区域——对带当年幼崽的雌性北极熊至关重要。其潜在成因可能包括可获取充足且可预测的猎物（环斑海豹幼崽）、能量保存需求，以及不愿跨越大面积开阔水域。然而，斯瓦尔巴群岛的冰川前缘正在退缩，过去十年间陆缘固定冰的消退尤为显著。这类重要栖息地的最终消失，可能会对斯瓦尔巴群岛及其他具有相似生境特征区域的北极熊幼崽生存构成致命威胁。鉴于斯瓦尔巴群岛多数固定冰区域面积相对较小，若采用精度更低的定位数据或分辨率更低的海冰数据，本研究的观测结果将无法被揭示。