van Gils Jan A, van der Geest Matthijs, De Meulenaer Brecht, Gillis Hanneke, Piersma Theunis, Folmer Eelke O
Department of Marine Ecology, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790, AB Den Burg, Texel, The Netherlands.
Chair in Global Flyway Ecology, Animal Ecology Group, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, PO Box 11103, 9700, CC Groningen, the Netherlands.
J Anim Ecol. 2015 Mar;84(2):554-64. doi: 10.1111/1365-2656.12301. Epub 2014 Oct 31.
Models relating intake rate to food abundance and competitor density (generalized functional response models) can predict forager distributions and movements between patches, but we lack understanding of how distributions and small-scale movements by the foragers themselves affect intake rates. Using a state-of-the-art approach based on continuous-time Markov chain dynamics, we add realism to classic functional response models by acknowledging that the chances to encounter food and competitors are influenced by movement decisions, and, vice versa, that movement decisions are influenced by these encounters. We used a multi-state modelling framework to construct a stochastic functional response model in which foragers alternate between three behavioural states: searching, handling and moving. Using behavioural observations on a molluscivore migrant shorebird (red knot, Calidris canutus canutus), at its main wintering area (Banc d'Arguin, Mauritania), we estimated transition rates between foraging states as a function of conspecific densities and densities of the two main bivalve prey. Intake rate decreased with conspecific density. This interference effect was not due to decreased searching efficiency, but resulted from time lost to avoidance movements. Red knots showed a strong functional response to one prey (Dosinia isocardia), but a weak response to the other prey (Loripes lucinalis). This corroborates predictions from a recently developed optimal diet model that accounts for the mildly toxic effects due to consuming Loripes. Using model averaging across the most plausible multi-state models, the fully parameterized functional response model was then used to predict intake rate for an independent data set on habitat choice by red knot. Comparison of the sites selected by red knots with random sampling sites showed that the birds fed at sites with higher than average Loripes and Dosinia densities, that is sites for which we predicted higher than average intake rates. We discuss the limitations of Holling's classic functional response model which ignores movement and the limitations of contemporary movement ecological theory that ignores consumer-resource interactions. With the rapid advancement of technologies to track movements of individual foragers at fine spatial scales, the time is ripe to integrate descriptive tracking studies with stochastic movement-based functional response models.
将摄食率与食物丰度和竞争者密度相关联的模型（广义功能反应模型）可以预测觅食者在斑块间的分布和移动，但我们尚不清楚觅食者自身的分布和小规模移动是如何影响摄食率的。通过基于连续时间马尔可夫链动力学的先进方法，我们在经典功能反应模型中加入了现实因素，即认识到遇到食物和竞争者的机会受移动决策影响，反之，移动决策也受这些相遇情况的影响。我们使用多状态建模框架构建了一个随机功能反应模型，其中觅食者在三种行为状态之间交替：搜索、处理和移动。通过对一种以软体动物为食的迁徙滨鸟（红腹滨鹬，Calidris canutus canutus）在其主要越冬地（毛里塔尼亚的阿尔金滩）的行为观察，我们估计了觅食状态之间的转换率，该转换率是同种密度和两种主要双壳类猎物密度的函数。摄食率随同种密度增加而降低。这种干扰效应并非由于搜索效率降低，而是因躲避移动而损失时间所致。红腹滨鹬对一种猎物（等波纹巴非蛤，Dosinia isocardia）表现出强烈的功能反应，但对另一种猎物（亮樱蛤，Loripes lucinalis）反应较弱。这证实了最近开发的一个最优饮食模型的预测，该模型考虑了摄食亮樱蛤所产生的轻微毒性影响。通过对最合理的多状态模型进行模型平均，然后使用完全参数化的功能反应模型来预测红腹滨鹬在栖息地选择的独立数据集上的摄食率。将红腹滨鹬选择的地点与随机抽样地点进行比较，结果表明，这些鸟类在亮樱蛤和等波纹巴非蛤密度高于平均水平的地点觅食，即我们预测摄食率高于平均水平的地点。我们讨论了忽略移动的霍林经典功能反应模型的局限性以及忽略消费者 - 资源相互作用的当代移动生态理论的局限性。随着在精细空间尺度上跟踪个体觅食者移动的技术迅速发展，将描述性跟踪研究与基于随机移动的功能反应模型相结合的时机已经成熟。
