Social correlates of variation in urinary cortisol in wild male bonobos (Pan paniscus)

► In the absence of estrous females, cortisol levels of wild ranging bonobo males were not related to dominance rank. ► In the presence of estrous females male cortisol levels correlate positively with dominance rank. ► Associations with estrous females explained between-individual variation in cortisol better than aggression. ► Aggression received by males and females can explain the within-individual variation in cortisol levels.