Winter Gabe, Wirsching Luis, Schielzeth Holger
Population Ecology Group, Institute of Ecology and Evolution, Friedrich Schiller University Jena, Dornburger Straße 159, 07743 Jena, Germany.
Behav Ecol. 2023 Jun 13;34(5):741-750. doi: 10.1093/beheco/arad047. eCollection 2023 Sep-Oct.
(Un)predictability has only recently been recognized as an important dimension of animal behavior. Currently, we neither know if (un)predictability encompasses one or multiple traits nor how (un)predictability is dependent on individual conditions. Knowledge about condition dependence, in particular, could inform us about whether predictability or unpredictability is costly in a specific context. Here, we study the condition dependence of (un)predictability in the escape behavior of the steppe grasshopper . Predator-prey interactions represent a behavioral context in which we expect unpredictability to be particularly beneficial. By exposing grasshoppers to an immune challenge, we explore if individuals in poor condition become more or less predictable. We quantified three aspects of escape behavior (flight initiation distance, jump distance, and jump angle) in a standardized setup and analyzed the data using a multivariate double-hierarchical generalized linear model. The immune challenge did not affect (un)predictability in flight initiation distance and jump angle, but decreased unpredictability in jump distances, suggesting that unpredictability can be costly. Variance decomposition shows that 3-7% of the total phenotypic variance was explained by individual differences in (un)predictability. Covariation between traits was found both among averages and among unpredictabilities for one of the three trait pairs. The latter might suggest an (un)predictability syndrome, but the lack of (un)predictability correlation in the third trait suggests modularity. Our results indicated condition dependence of (un)predictability in grasshopper escape behavior in one of the traits, and illustrate the value of mean and residual variance decomposition for analyzing animal behavior.
（不可）预测性直到最近才被视为动物行为的一个重要维度。目前，我们既不知道（不可）预测性是包含一个还是多个特征，也不清楚（不可）预测性如何依赖于个体状况。特别是关于状况依赖性的知识，可以让我们了解在特定情境中可预测性或不可预测性是否代价高昂。在此，我们研究草原蝗虫逃避行为中（不可）预测性的状况依赖性。捕食者与猎物的相互作用代表了一种行为情境，我们预计不可预测性在其中会特别有益。通过使蝗虫面临免疫挑战，我们探究状况不佳的个体是否变得更具或更不具可预测性。我们在一个标准化设置中量化了逃避行为的三个方面（飞行起始距离、跳跃距离和跳跃角度），并使用多变量双层次广义线性模型分析数据。免疫挑战并未影响飞行起始距离和跳跃角度的（不可）预测性，但降低了跳跃距离的不可预测性，这表明不可预测性可能是有代价的。方差分解表明，总表型方差的3 - 7%可由（不可）预测性的个体差异来解释。在三个特征对中的一对特征的平均值之间以及不可预测性之间都发现了特征协变。后者可能暗示存在一种（不可）预测性综合征，但第三个特征缺乏（不可）预测性相关性表明存在模块性。我们的结果表明蝗虫逃避行为中一个特征的（不可）预测性存在状况依赖性，并说明了均值和残差方差分解在分析动物行为方面的价值。
