Styles of dominance and their endocrine correlates among wild olive baboons (Papio anubis)

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Abstract
We have studied the relationship between dominance rank and physiology among male olive baboons (Papio anubis) living freely in a national park in Africa. In stable hierarchies, dominant males consistently have lower basal concentrations than do subordinates of the adrenal glucocorticoid cortisol. Because of the known catabolic actions of glucocorticoids, dominant males may be less at risk for some of the pathogenic consequences of glucocorticoid overexposure. We find that low basal cortisol concentration is not, in fact, a marker of social dominance; instead, it is only found among dominant males with a certain style of dominance. Lower basal cortisol concentrations occurred among males with any of the following behaviors: the most marked ability to distinguish between threatening and merely neutral interactions with rivals and, if the former, the greatest likelihood of initiating a fight; the most skill at distinguishing between winning and losing a fight and, if the latter, the greatest likelihood of displacing aggression onto a third party. Collectively, these behaviors suggest high degrees of social skillfulness, control, and predictability over social contingencies, all recognized as psychological features that minimize the pathophysiological impact of stress. Dominant males lacking these behavioral features, in contrast, had as high cortisol concentrations as did subordinate males. Finally, low basal cortisol concentrations were also a feature of males with the longest tenures in the dominant cohort, suggesting that this endocrine dichotomy is meaningful in terms of life histories.