In ecology, the concept of predation describes interdependent patterns of having one species (called the predator) killing and consuming another (the prey). Specifying the so-called functional response of prey populations to predation is an important matter of debate which is typically addressed by means of continuous time models. Empirical regression or autoregression models applied to discrete predator-prey population data promise feasible steady state approximations of often complicated dynamic patterns of population growth and interaction. Ewing et al. (Ecol Econ 60:605–612, 2007) argue in favour of the informational content of so-called vector autoregressive models for the dynamic analysis of predator-prey systems. In this work we reconsider their analysis of dynamic interaction of two freshwater organisms, and design a structural model that allows to approximate the functional response in causal form. Results from an unrestricted structural model are in line with core axiomatic assumptions of predator-prey models. Conditional on population growth lagged up to three periods (i.e., 36 h), the semi-daily population growth of the prey Paramecium aurelia diminishes, on average, by 1.2 percentage points in response to an increase of the population growth of the predator Didinium nasutum by one percentage point.

在生态学中，捕食的概念描述了一种物种（称为捕食者）杀死并消耗另一种物种（捕食者）的相互依存模式。确定所谓的猎物种群对捕食的功能反应是一个重要的辩论问题，通常通过连续时间模型来解决。应用于离散捕食者-被捕食者种群数据的经验回归或自回归模型有望为通常复杂的种群增长和相互作用动态模式提供可行的稳态近似。Ewing等。（Ecol Econ 60：605-612，2007）主张对所谓的向量自回归模型的信息内容进行捕食者—猎物系统的动态分析。在这项工作中，我们重新考虑了他们对两种淡水生物的动态相互作用的分析，并设计一个结构模型，以近似因果形式的功能响应。无限制结构模型的结果与捕食者－猎物模型的核心公理假设相符。在不超过三个时期（即36小时）的前提下，捕食者的种群每天半日增长由于捕食者Didinium nasutum的种群增长增加了一个百分点，因此草履虫的平均含量降低了1.2个百分点。