Department of Animal Behaviour, Bielefeld University, Bielefeld, Germany.
Department of Business Administration and Economics, Bielefeld University, Bielefeld, Germany.
Oecologia. 2021 Feb;195(2):313-325. doi: 10.1007/s00442-021-04850-w. Epub 2021 Jan 24.
Foraging strategies are of great ecological interest, as they have a strong impact on the fitness of an individual and can affect its ability to cope with a changing environment. Recent studies on foraging strategies show a higher complexity than previously thought due to intraspecific variability. To reliably identify foraging strategies and describe the different foraging niches they allow individual animals to realize, high-resolution multivariate approaches which consider individual variation are required. Here we dive into the foraging strategies of Galápagos sea lions (Zalophus wollebaeki), a tropical predator confronted with substantial annual variation in sea surface temperature. This affects prey abundance, and El Niño events, expected to become more frequent and severe with climate change, are known to have dramatic effects on sea lions. This study used high-resolution measures of depth, GPS position and acceleration collected from 39 lactating sea lion females to analyze their foraging strategies at an unprecedented level of detail using a novel combination of automated broken stick algorithm, hierarchical cluster analysis and individually fitted multivariate hidden Markov models. We found three distinct foraging strategies (pelagic, benthic, and night divers), which differed in their horizontal, vertical and temporal distribution, most likely corresponding to different prey species, and allowed us to formulate hypotheses with regard to adaptive values under different environmental scenarios. We demonstrate the advantages of our multivariate approach and inclusion of individual variation to reliably gain a deeper understanding of the adaptive value and ecological relevance of foraging strategies of marine predators in dynamic environments.
觅食策略具有重要的生态意义，因为它们对个体的适应性有很大的影响，并能影响其应对环境变化的能力。由于种内变异性，最近对觅食策略的研究显示出比以前想象的更高的复杂性。为了可靠地识别觅食策略并描述它们允许个体动物实现的不同觅食生态位，需要考虑个体变异的高分辨率多元方法。在这里，我们深入研究了加拉帕戈斯海狮（Zalophus wollebaeki）的觅食策略，这是一种热带捕食者，面临着海面温度的巨大年度变化。这会影响猎物的丰度，而预计随着气候变化，厄尔尼诺现象将变得更加频繁和严重，这对海狮有巨大的影响。本研究使用了从 39 只哺乳期雌性海狮收集的深度、GPS 位置和加速度的高分辨率测量数据，使用自动折断棒算法、层次聚类分析和个体拟合多元隐马尔可夫模型的新组合，以前所未有的细节水平分析了它们的觅食策略。我们发现了三种不同的觅食策略（远洋、底栖和夜间潜水），它们在水平、垂直和时间分布上存在差异，这很可能对应于不同的猎物种类，并使我们能够针对不同环境情景下的适应价值提出假设。我们展示了我们的多元方法和个体变异的纳入的优势，以可靠地深入了解动态环境中海洋捕食者的觅食策略的适应价值和生态相关性。
