Assessment of scale-dependent foraging behaviour in southern elephant seals incorporating the vertical dimension: a development of the First Passage Time method
Assessment of scale-dependent foraging behaviour in southern elephant seals incorporating the vertical dimension: a development of the First Passage Time method
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DOI：
10.1111/j.1365-2656.2008.01407.x
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发表时间：
2008-09-01
影响因子：
4.8
通讯作者：
Guinet, Christophe
中科院分区：
文献类型：
--
作者：
Bailleul, Frederic;Pinaud, David;Guinet, Christophe
1. 确定顶级海洋捕食者觅食的空间尺度对于理解海洋生态系统至关重要。有几种方法可以量化个体如何沿着给定路径集中其搜索努力。其中，首次通过时间（FPT）分析对于识别运动模式的转变（例如在搜索和进食之间）特别有用。这种方法主要应用于陆地动物或飞行的海鸟，它们的觅食几乎没有或没有垂直成分，因此我们研究了经典FPT与使用潜水底部停留时间来表征一种潜水捕食者——南象海豹的觅食活动的这种方法的改进之间的差异。
2. 在克尔格伦群岛连续三个夏季期间，在20个个体上部署了卫星中继数据记录器，从8只幼年雄性和9只成年雌性个体中总共获得了72978次潜水数据。
3. 使用潜水底部停留时间确定的空间尺度（$\bar{\omega}$ = 68.2 ± 42.1千米）比通过经典FPT分析获得的空间尺度（$\bar{\omega}$ = 104.7 ± 67.3千米）要小。此外，使用新方法确定的觅食区域与个体身体状况改善的区域明显重叠，这表明它准确地反映了海豹的觅食活动。
4. 这些结果表明，将垂直维度纳入FPT所提供的结果与仅考虑表面路径的结果不同。在南极大陆附近的浮冰区内，路径的曲折可以用高海冰浓度（限制象海豹的移动）来解释，而不一定与觅食活动有关。
5. 我们的方法区分了实际的觅食活动和由海冰等物理环境引起的行为变化，并且可以应用于其他潜水捕食者。纳入潜水参数似乎对于确定潜水动物觅食区域的空间尺度至关重要。
1. Identifying the spatial scales at which top marine predators forage is important for understanding oceanic ecosystems. Several methods quantify how individuals concentrate their search effort along a given path. Among these, First-Passage Time (FPT) analysis is particularly useful to identify transitions in movement patterns (e.g. between searching and feeding). This method has mainly been applied to terrestrial animals or flying seabirds that have little or no vertical component to their foraging, so we examined the differences between classic FPT and a modification of this approach using the time spent at the bottom of a dive for characterizing the foraging activity of a diving predator: the southern elephant seal.2. Satellite relayed data loggers were deployed on 20 individuals during three successive summers at the Kerguelen Islands, providing a total of 72 978 dives from eight juvenile males and nine adult females.3. Spatial scales identified using the time spent at the bottom of a dive ((omega) over bar = 68.2 +/- 42.1 km) were smaller than those obtained by the classic FPT analysis ((omega) over bar = 104.7 +/- 67.3 km). Moreover, foraging areas identified using the new approach clearly overlapped areas where individuals increased their body condition, indicating that it accurately reflected the foraging activity of the seals.4. These results suggest that incorporating the vertical dimension into FPT provides a different result to the surface path alone. Close to the Antarctic continent, within the pack-ice, sinuosity of the path could be explained by a high sea-ice concentration (restricting elephant seal movements), and was not necessarily related to foraging activity.5. Our approach distinguished between actual foraging activity and changes in behaviour induced by the physical environment like sea ice, and could be applied to other diving predators. Inclusion of diving parameters appears to be essential to identify the spatial scale of foraging areas of diving animals.