Marine Predator Unit, Institute of Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia.
Ecology. 2011 Jun;92(6):1258-70. doi: 10.1890/09-1299.1.
Predators are thought to reduce travel speed and increase turning rate in areas where resources are relatively more abundant, a behavior termed "area-restricted search." However, evidence for this is rare, and few empirical data exist for large predators. Animals exhibiting foraging site fidelity could also be spatially aware of suitable feeding areas based on prior experience; changes in movement patterns might therefore arise from the anticipation of higher prey density. We tested the hypothesis that regions of area-restricted search were associated with a higher number of daily speed spikes (a proxy for potential prey encounter rate) and foraging success in southern elephant seals (Mirounga leonina), a species exhibiting both area-restricted searches and high interannual foraging site fidelity. We used onshore morphological measurements and diving data from archival tags deployed during winter foraging trips. Foraging success was inferred from in situ changes in relative lipid content derived from measured changes in buoyancy, and first-passage time analysis was used to identify area-restricted search behavior. Seals exhibited relatively direct southerly movement on average, with intensive search behavior predominantly located at the distal end of tracks. The probability of being in search mode was positively related to changes in relative lipid content; thus, intensively searched areas were associated with the highest foraging success. However, there was high foraging success during the outward transit even though seals moved through quickly without slowing down and increasing turning rate to exploit these areas. In addition, the probability of being in search mode was negatively related to the number of daily speed spikes. These results suggest that movement patterns represent a response to prior expectation of the location of predictable and profitable resources. Shelf habitat was 4-9 times more profitable than the other habitats, emphasizing the importance of the East Antarctic shelf for this and other predators in the region. We have provided rare empirical data with which to investigate the relationship between predator foraging strategy and prey encounter/ foraging success, underlining the importance of inferring the timing and spatial arrangement of successful food acquisition for interpreting foraging strategies correctly.
捕食者被认为会在资源相对丰富的区域降低移动速度并增加转弯率，这种行为被称为“区域限制搜索”。然而，这种行为的证据很少，并且针对大型捕食者的实证数据也很少。表现出觅食地忠诚度的动物也可能基于先前的经验而对适宜的觅食区域具有空间感知；因此，移动模式的变化可能源于对更高猎物密度的预期。我们测试了以下假设，即区域限制搜索区域与每日速度峰值（潜在猎物遭遇率的代理）的数量以及南部象海豹（Mirounga leonina）的觅食成功率有关，该物种既表现出区域限制搜索行为，又表现出高度的年度觅食地忠诚度。我们使用了在冬季觅食期间部署的档案标签的陆上形态测量和潜水数据。通过从浮力变化中得出的相对脂质含量的原位变化来推断觅食成功率，并且使用首次通过时间分析来识别区域限制搜索行为。海豹的平均运动方向相对直接向南，主要在轨迹的末端进行密集搜索。处于搜索模式的概率与相对脂质含量的变化呈正相关；因此，密集搜索区域与最高的觅食成功率相关。然而，即使海豹在快速移动而没有减速并增加转弯率以利用这些区域时，在向外迁移过程中仍有很高的觅食成功率。此外，处于搜索模式的概率与每日速度峰值的数量呈负相关。这些结果表明，运动模式代表了对可预测和有利资源位置的先前预期的反应。大陆架生境的效益是其他生境的 4-9 倍，强调了东南极洲大陆架对该地区的这种捕食者和其他捕食者的重要性。我们提供了罕见的实证数据，用于研究捕食者觅食策略与猎物遭遇/觅食成功率之间的关系，强调了正确解释觅食策略的重要性，即推断成功获取食物的时间和空间安排。
