In vertebrates, glucocorticoid secretion occurs in response to energetic and psychosocial stressors that trigger the hypothalamic-pituitary-adrenal (HPA) axis. Measuring glucocorticoid concentrations can therefore shed light on the stressors associated with different social and environmental variables, including dominance rank. Using 14,172 fecal samples from 237 wild female baboons, we test the hypothesis that high-ranking females experience fewer psychosocial and/or energetic stressors than lower-ranking females. We predicted that high-ranking females would have lower fecal glucocorticoid (fGC) concentrations than low-ranking females. Because dominance rank can be measured in multiple ways, we employ an information theoretic approach to compare 5 different measures of rank as predictors of fGC concentrations: ordinal rank; proportional rank; Elo rating; and two approaches to categorical ranking (alpha vs non-alpha and high-middle-low). Our hypothesis was supported, but it was also too simplistic. We found that alpha females exhibited substantially lower fGCs than other females (typical reduction = 8.2%). If we used proportional rank instead of alpha versus non-alpha status in the model, we observed a weak effect of rank such that fGCs rose 4.2% from the highest- to lowest-ranking female in the hierarchy. Models using ordinal rank, Elo rating, or high-middle-low categories alone failed to explain variation in female fGCs. Our findings shed new light on the association between dominance rank and the stress response, the competitive landscape of female baboons as compared to males, and the assumptions inherent in a researcher's choice of rank metric.

在脊椎动物中，糖皮质激素的分泌是对触发下丘脑-垂体-肾上腺 (HPA) 轴的能量和心理压力源的反应。因此，测量糖皮质激素浓度可以揭示与不同社会和环境变量（包括优势等级）相关的压力源。我们使用来自 237 只野生雌性狒狒的 14,172 份粪便样本，检验了以下假设：与地位较低的雌性相比，地位较高的雌性狒狒经历的社会心理和/或精力压力较少。我们预测，地位高的女性粪便糖皮质激素（fGC）浓度低于地位低的女性。由于优势等级可以通过多种方式测量，因此我们采用信息论方法来比较 5 种不同的等级测量作为 fGC 浓度的预测因子：序数等级；比例等级；Elo 评级；以及两种分类排名方法（阿尔法与非阿尔法以及高-中-低）。我们的假设得到了支持，但也过于简单化了。我们发现，阿尔法雌性表现出比其他雌性低得多的 fGC（典型降低 = 8.2%）。如果我们在模型中使用比例排名而不是 alpha 与非 alpha 状态，我们会观察到排名的微弱影响，使得 fGC 从层次结构中排名最高的女性到最低排名的女性上升了 4.2%。单独使用序数等级、Elo 等级或高-中-低类别的模型无法解释女性 fGC 的变化。我们的研究结果为以下方面提供了新的线索：支配等级与压力反应之间的关联、雌性狒狒与雄性狒狒相比的竞争格局，以及研究人员选择等级指标时固有的假设。