Data from: Rewriting the history of an extinction - was a population of Steller's sea cows (Hydrodamalis gigas) at St. Lawrence Island also driven to extinction?

The Kommandorskiye Islands population of Steller's sea cow (Hydrodamalis gigas) was extirpated ca 1768 CE. Until now, Steller's sea cow was thought to be restricted in historic times to Bering and Copper Islands, Russia, with other records in the last millennium from the western Aleutian Islands. However, Steller's sea cow bone has been obtained by the authors from St Lawrence Island, Alaska, which is significantly further north. Bone identity was verified using analysis of mitochondrial DNA. The nitrogen-15 (δ15N)/carbon-13 (δ13C) values for bone samples from St Lawrence Island were significantly (p ≤ 0.05) different from Bering Island samples, indicating a second population. Bone samples were dated to between 1030 and 1150 BP (approx. 800–920 CE). The samples date from close to the beginning of the mediaeval warm period, which could indicate that the population at St Lawrence Island was driven to extinction by climate change. A warming of the climate in the area may have changed the availability of kelp; alternatively or in addition, the animals may have been driven to extinction by the expansion of the Inuit from the Bering Strait region, possibly due to opening waterways, maybe following bowhead whales (Balaena mysticetus), or searching for iron and copper. This study provides evidence for a previously unknown population of sea cows in the North Pacific within the past 1000 years and a second Steller's sea cow extirpation event in recent history.

斯特勒海牛（Hydrodamalis gigas）的科曼多尔群岛种群已于公元1768年左右彻底灭绝。此前学界一直认为，历史时期内斯特勒海牛的分布仅局限于俄罗斯的白令岛与科珀岛，而过去千年里的其他记录仅来自阿留申群岛西部。但本研究作者从阿拉斯加圣劳伦斯岛获取了斯特勒海牛的骨骼标本，该区域纬度远高于此前已知分布区。研究通过线粒体DNA（mitochondrial DNA）分析验证了骨骼的物种归属。圣劳伦斯岛骨骼样本的氮15（δ15N）/碳13（δ13C）值与白令岛样本存在显著差异（p ≤ 0.05），表明存在第二个斯特勒海牛种群。经年代测定，这些骨骼样本的年代介于1030至1150个距今（Before Present，BP），对应公元800至920年左右。样本年代接近中世纪暖期（mediaeval warm period）的起始阶段，这提示圣劳伦斯岛的斯特勒海牛种群可能因气候变化走向灭绝。该区域气候变暖可能改变了巨藻的可获得性；此外或取而代之的是，因纽特人（Inuit）从白令海峡（Bering Strait）地区向外扩张，可能借助通航水道追踪弓头鲸（Balaena mysticetus），或为搜寻铁、铜资源，从而导致斯特勒海牛被猎杀至灭绝。本研究为过去千年里北太平洋地区存在此前未被发现的斯特勒海牛种群提供了证据，同时也证实了近代史上斯特勒海牛的第二次局部灭绝事件。