Searching for prey in a three-dimensional environment: hierarchical movements enhance foraging success in northern elephant seals
Searching for prey in a three-dimensional environment: hierarchical movements enhance foraging success in northern elephant seals
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DOI：
10.1111/1365-2435.12686
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发表时间：
2017-02-01
影响因子：
5.2
通讯作者：
Takahashi, Akinori
中科院分区：
文献类型：
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作者：
Adachi, Taiki;Costa, Daniel P.;Takahashi, Akinori
1.觅食理论预测，捕食者会根据猎物的空间分布来调整自己的行动。由于猎物往往是斑块分布，区域限制搜索（ARS）的行为，其特点是曲折的搜索路径的捕食者增加转向频率，应该是有效的觅食。然而，目前还不清楚ARS行为是否真的提高了自由迁徙动物的觅食成功率，特别是在三维（3D）环境中觅食的海洋动物。在这里，我们重建了三维潜水路径的高度远洋海洋捕食者，北方海象（n = 3），与多传感器数据记录器，记录深度，三轴加速度，三轴磁力和游泳速度。我们使用三维潜水路径上的球形首次通过时间分析确定了体积限制搜索（VRS，称为3D ARS）行为的空间尺度，并通过使用下颌骨加速度计记录进食事件来量化VRS中的进食率。海豹在两个空间尺度（球体半径）上表现出VRS行为：小VRS（8-10米）和大VRS（17-19米）。大多数喂养事件发生在VRS区（78%和86%的小和大VRS，分别），虽然VRS占一小部分的底部阶段的潜水距离旅行。这表明VRS行为和觅食成功之间有很强的联系。VRS存在分层结构;大多数小VRS（95%）嵌套在大VRS内（即，e.嵌套VRS）。重要的是，巢式VRS有显着更高的喂养率比非巢式VRS，因为巢式VRS包含小和大VRS的较高和较低的喂养率，分别。这些结果表明，海豹在一个等级斑块系统中捕食中层猎物，其中小尺度的高密度斑块嵌套在大尺度的低密度斑块中.我们证明，海豹采用规模依赖，分层三维运动和水下细尺度蜿蜒运动（即。e. VRS）与更高的觅食成功率密切相关，特别是在嵌套的VRS区域内。我们认为，海豹提高觅食的成功，采用层次运动，可能反映了猎物分布的层次属性。虽然最近的研究主张最佳搜索行为将是尺度无关的（e。G. Levy walk），我们的研究表明，规模依赖的过程是成功的觅食行为的重要组成部分。
1. Foraging theory predicts that predators adjust their movements according to the spatial distribution of prey. Since prey is often patchily distributed, area-restricted search (ARS) behaviour, characterized by sinuous search paths of predators with increased turning frequency, should be effective in foraging.2. However, it remains unclear whether ARS behaviour actually enhances foraging success in freeranging animals, especially in marine animals that forage in a three-dimensional (3D) environment.3. Here, we reconstructed 3D dive paths of a highly pelagic marine predator, the northern elephant seal (n = 3), with multisensor data loggers that recorded depth, tri-axis acceleration, tri-axis magnetism and swim speed. We identified spatial scales of volume-restricted search (VRS, termed for 3D ARS) behaviour using spherical first-passage time analysis on 3D dive paths, accompanied with quantifying feeding rates in VRS by using mandible accelerometers that recorded feeding events.4. Seals exhibited VRS behaviour at two spatial scales (radius of spheres): small-VRS (8-10 m) and large-VRS (17-19 m). Most feeding events occurred in VRS zones (78 and 86% for small and large-VRS, respectively), although VRS accounted for a small proportion of bottom phase of dives in distance travelled. This suggests a strong link between VRS behaviour and foraging success.5. There was a hierarchical structure to the VRS; most small-VRS (95%) were nested within large-VRS (i. e. nested VRS). Importantly, nested VRS had significantly higher feeding rates than non-nested VRS, because nested VRS contained small- and large-VRS with higher and lower feeding rates, respectively. These results suggest that seals forage on mesopelagic prey in a hierarchical patch system where high-density patches at small scales are nested within lowdensity patches at larger scales.6. We demonstrated that seals employed scale-dependent, hierarchical 3D movements and that underwater fine-scale sinuous movements (i. e. VRS) were strongly linked to higher foraging success, particularly within nested VRS zones. We suggest that seals enhanced foraging success by employing hierarchical movements that possibly reflect the hierarchical property of prey distribution. Although recent studies advocate that optimal searching behaviour would be scale-independent (e. g. Levy walk), our study suggests that scale-dependent processes are important components of successful foraging behaviour.