DataSheet_2_Relating polar bears killed, human presence, and ice conditions in Svalbard 1987–2019.pdf

Conflicts between humans and polar bears have been predicted to increase as polar bear prime habitat, sea ice, is decreasing. In Svalbard, a strict protection and control schemes have secured near complete records of bears killed and found dead since 1987. We analyzed the trend in the number of kills and related this to human visitation to the archipelago. We found a slight decrease in the number of kills in the period 1987-2019, and a decrease in per capita number of kills when monthly kills were compared to the monthly number of visitors disembarking in the main settlement. We then used a discrete choice resource selection model to assess whether polar bear kill events are related to attributes of the kill sites and environmental conditions at the time. We divided Svalbard in four sectors, North, East, South, and West, and monthly average ice cover was calculated in 25-km rings around Svalbard, rings that were further delineated by the four sectors. We found that the odds of a kill was greater along the shoreline, and that the odds would be reduced by 50% when moving only 900 m from the shoreline when all sectors were included. Distance from other covariates like settlements, trapper’s cabins, and landing sites for tourists did for the most part not have a significant impact on the odds of a kill. Sectorwise, ice cover had no significant impact on the odds for a kill. The decreasing trend in kills of polar bears might partly be explained by the success of strict protection and management regimes of Svalbard wilderness.

随着北极熊的核心栖息地——海冰——不断缩减，人类与北极熊之间的冲突预计将呈上升趋势。在斯瓦尔巴群岛（Svalbard），当地实施的严格保护与管控机制使得自1987年起，北极熊遭猎杀及被发现死亡的记录近乎完整。本研究对北极熊遭猎杀的数量变化趋势进行了分析，并将其与该群岛的人类到访情况进行关联。研究发现，1987年至2019年间，北极熊遭猎杀的数量略有下降；当以每月猎杀数与当月在主要定居点登岸的游客数量进行对比时，人均猎杀量亦呈下降趋势。随后，本研究采用离散选择资源选择模型（discrete choice resource selection model），评估北极熊猎杀事件是否与猎杀点的属性及当时的环境条件相关。研究将斯瓦尔巴群岛划分为北、东、南、西四个区域，并以群岛为中心划定25公里环形缓冲区，随后依据前述四个区域对各缓冲区进行细分，进而计算各区域的月平均海冰覆盖度。研究结果显示，猎杀事件发生在海岸线附近的优势比更高；当纳入所有区域进行分析时，每向远离海岸线方向移动900米，猎杀事件发生的优势比便会降低50%。其余协变量——如与定居点、捕熊者小屋及游客登岸点的距离——在多数情况下对猎杀事件发生的优势比无显著影响。分区域来看，海冰覆盖度对猎杀事件发生的优势比并无显著影响。北极熊遭猎杀数量的下降趋势，部分可归因于斯瓦尔巴群岛荒野地区严格的保护与管理制度所取得的成效。