This issue's cover shows a female Pacific walrus on an ice floe in the Chukchi Sea. Walrus habitat is remote and difficult to access, making it challenging to study the life history of these iconic Arctic mammals. In their article, Clark et al. explore the use of strontium and barium in walrus teeth as indicators of weaning age. Pacific walruses are an important food resource for Russian and Alaska Native communities, and walrus teeth are collected during subsistence harvests to monitor the age structure of hunted animals. Growth layers in teeth archive a lifetime record of trace element concentrations in an animal's body, and specific patterns of accumulation of strontium and barium have been associated with nursing and weaning in some terrestrial mammals. Age‐at‐weaning is reflective of maternal investment, which is linked to the health and nutritional status of the mother. The ability to determine weaning age by examining patterns in walrus tooth cementum adds a valuable tool to the arsenal of wildlife managers, and may provide important insight into the status of walrus populations as the Arctic continues to change. Credit: U.S. Fish and Wildlife Service, Casey Clark.

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封面图片和发行信息

本期杂志的封面显示了在楚科奇海的一块浮冰上的一只雌性太平洋海象。海象栖息地偏远且难以进入，因此难以研究这些标志性的北极哺乳动物的生活史。在他们的文章中，克拉克等。探索在海象齿中使用锶和钡作为断奶年龄的指标。太平洋海象是俄罗斯和阿拉斯加土著社区的重要食物资源，海象牙在维持生计的过程中收集，以监测被猎杀动物的年龄结构。牙齿上的生长层记录了动物体内微量元素浓度的终生记录，并且锶和钡的特定积累模式与某些陆生哺乳动物的哺乳和断奶有关。断奶年龄反映了产妇的投资，这与母亲的健康和营养状况有关。通过检查海象牙牙骨质的形态来确定断奶年龄的能力为野生动植物管理者的军备库提供了宝贵的工具，并且随着北极的不断变化，可能为海象种群的状况提供重要的见识。图片提供：美国鱼类和野生动物管理局，凯西·克拉克（Casey Clark）。