Animals often exhibit consistent individual differences in behavior (i.e. animal personality) and correlations between behaviors (i.e. behavioral syndromes), yet the causes of those patterns of behavioral variation remain insufficiently understood. Many authors hypothesize that state-dependent behavior produces animal personality and behavioral syndromes. However, empirical studies assessing patterns of covariation among behavioral traits and state variables have produced mixed results. New statistical methods that partition correlations into between-individual and residual within-individual correlations offer an opportunity to more sufficiently quantify relationships among behaviors and state variables to assess hypotheses of animal personality and behavioral syndromes. In a population of wild Belding's ground squirrels (Urocitellus beldingi) we repeatedly measured activity, exploration, and response to restraint behaviors alongside glucocorticoids and nutritional condition. We used multivariate mixed models to determine whether between-individual or within-individual correlations drive phenotypic relationships among traits. Squirrels had consistent individual differences for all five traits. At the between-individual level, activity and exploration were positively correlated whereas both traits negatively correlated with response to restraint, demonstrating a behavioral syndrome. At the within-individual level, condition negatively correlated with cortisol, activity and exploration. Importantly, this indicates that although behavior is state-dependent, which may play a role in animal personality and behavioral syndromes, feedback mechanisms between condition and behavior appear not to produce consistent individual differences in behavior and correlations between them.

中文翻译：

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个体内相关性揭示了自由放养的贝尔丁地松鼠的行为综合症、状况和皮质醇之间的联系

动物通常表现出一致的行为个体差异（即动物个性）和行为之间的相关性（即行为综合症），但这些行为变异模式的原因仍不清楚。许多作者假设状态依赖行为会产生动物性格和行为综合症。然而，评估行为特征和状态变量之间的协变模式的实证研究产生了不同的结果。将相关性分为个体间相关性和个体内残留相关性的新统计方法提供了一个机会，可以更充分地量化行为和状态变量之间的关系，以评估动物性格和行为综合症的假设。在野生贝尔丁地松鼠（Urocitellus beldingi）种群中，我们反复测量活动、探索和对约束行为的反应以及糖皮质激素和营养状况。我们使用多变量混合模型来确定个体之间或个体内部的相关性是否驱动性状之间的表型关系。松鼠的所有五个特征都具有一致的个体差异。在个体之间的水平上，活动和探索呈正相关，而这两种特征都与对约束的反应呈负相关，这表明行为综合症。在个体内部水平上，状况与皮质醇、活动和探索呈负相关。重要的是，这表明虽然行为是状态依赖性的，这可能在动物性格和行为综合症中发挥作用，但条件和行为之间的反馈机制似乎不会产生一致的行为个体差异及其之间的相关性。