100-6 Sat Jan 2 Alpha female baboons have the lowest glucocorticoid levels: What we can learn from comparing rank metrics Levy, EJ*; Gesquiere, LR; McLean, E; Franz, M; Warutere, JK; Sayialel, SN; Mututua, RS; Wango, TL; Oudu, VK; Altmann, J; Archie, EA; Alberts, SC; Duke University; Duke University; Oxford College of Emory University; Freie Universitaet Berlin; Amboseli Baboon Research Project; Amboseli Baboon Research Project; Amboseli Baboon Research Project; University of Nairobi; Amboseli Baboon Research Project; Princeton University; University of Notre Dame; Duke University ejl37@duke.edu http://emilyjlevy.weebly.com/
In group-living animals, dominance hierarchies are a common cause of unequal access to fitness-related resources. There are many different methods to measure dominance rank, including ordinal rank, proportional rank (i.e., standardized or relative rank), high-middle-low categories, alpha versus non-alpha status, and cardinal rank measures (e.g., Elo rating). We hypothesize that each rank metric makes a different assumption about resource availability and within-group competition. Using a large dataset of fecal samples from wild adult female baboons, we test the ability of five common rank metrics to predict fecal glucocorticoid concentrations as a proxy for psychosocial and energetic stressors. Surprisingly, alpha status was the best predictor of fecal glucocorticoids, with lower levels in alpha females relative to non-alphas, indicating fewer stressors experienced by alpha females relative to other adult females. We also observed a weak effect of proportional rank, with lower fecal glucocorticoids in high-ranking females than low-ranking females. Our work introduces a new and easy approach to gain insight into the competitive landscapes occurring in animal societies.
