Graduate School of Environmental Studies, Nagoya University, Nagoya, Aichi 464-8601, Japan.
Graduate School of Environmental Studies, Nagoya University, Nagoya, Aichi 464-8601, Japan.
Curr Biol. 2019 Jan 7;29(1):R12-R13. doi: 10.1016/j.cub.2018.11.023.
Magellanic penguins (Spheniscus magellanicus) have been reported to become stranded along the coasts of northern Argentina, Uruguay and southern Brazil during the austral winter [1-3]. This location is more than a thousand kilometers distant from their northernmost breeding colony in northern Patagonia. Curiously, females typically outnumber males at stranding sites (approximately three females per male) [2]. To date, no conspicuous sex differences have been reported in their migratory movements [3], although records are lacking during the peak stranding season. Consequently, the reason(s) for the female-biased stranding remain unknown, despite the growing necessity for understanding their behavior outside the breeding season [3]. We recorded at-sea distributions of Magellanic penguins throughout the non-breeding period using animal-borne data loggers and found that females reached more northern areas than males and did not dive as deep during winter (Figure 1). Such sexual differences in spatial domains might be driven by mechanisms related to sexual size dimorphism, such as the avoidance of intraspecific competition for food resources [4], differences in thermal habitat preference [5] or differences in the ability to withstand the northward-flowing ocean circulation [6]. Individual penguins that winter in northern areas are likely to be at greater risk of natural [7] and anthropogenic threats [8], and probably more so in females, as more females than males tend to frequent areas closer to the sites where penguins strand. Our results highlight the importance of understanding the spatial domains of each sex throughout the annual cycle that are associated with different mortality risks.
麦哲伦企鹅（Spheniscus magellanicus）在南半球的冬季曾被报道在阿根廷北部、乌拉圭和巴西南部的海岸搁浅[1-3]。这个地点距离它们在巴塔哥尼亚北部的最北繁殖地有一千多公里。奇怪的是，在搁浅地点，雌性通常比雄性多（大约每三只雌性对应一只雄性）[2]。到目前为止，它们在迁徙过程中没有明显的性别差异[3]，尽管在高峰期搁浅季节缺乏记录。因此，尽管在繁殖季节之外了解它们的行为变得越来越必要，但雌性偏向搁浅的原因仍不清楚[3]。我们使用动物携带的数据记录器记录了整个非繁殖期麦哲伦企鹅的海上分布情况，发现雌性到达的北部地区比雄性多，并且在冬季潜水不深（图 1）。这种在空间领域的性别差异可能是由与性二型相关的机制驱动的，例如避免同种竞争食物资源[4]、对热栖息地偏好的差异[5]或承受向北流动的海洋环流的能力的差异[6]。在北部地区过冬的个体企鹅可能面临更大的自然[7]和人为威胁[8]，而雌性面临的威胁可能更大，因为与雄性相比，更多的雌性倾向于经常光顾靠近企鹅搁浅地点的区域。我们的研究结果强调了在整个年度周期中了解每个性别的空间领域的重要性，这些领域与不同的死亡率风险相关。
