Urinary testosterone metabolite levels and aggressive behaviors in male and female Bonobos (Pan paniscus)

This study presents the first data on the relationship between testosterone (T) and aggression in both sexes of the bonobo (Pan paniscus). Morning urinary concentrations of T metabolites (measured by immunoreactive 5alpha-androstane-17alpha-ol-3-one) were used to reflect T status. Results show that first, no correlation of T metabolite levels with any of the aggressive behaviors was found between individuals. Within an individual, T metabolite levels only correlated with a minority of aggressive behaviors. Hence, social factors are likely of major importance for the occurrence of aggression in this highly gregarious species, but certain intraindividual aspects of aggressive behavior are nevertheless related to T. A more detailed discussion of the results follows. Secondly, all correlations with T were similar for every individual, males and females, suggesting an analogous relationship in both sexes. Thirdly, our study confirms for bonobos that the measure of aggression used, the time scale at which the correlation is studied, and whether this is done on an inter- or intraindividual level, considerably affect results. (C) 2004 Wiley-Liss, Inc.