CSF 5-HIAA, TESTOSTERONE, AND SOCIOSEXUAL BEHAVIORS IN FREE-RANGING MALE RHESUS MACAQUES IN THE MATING SEASON

This study examines sexual behavior, serotonin turnover in the central nervous system, and testosterone in free-ranging non-human primates. Study subjects were 33 young adult male rhesus macaques (Macaca mulatt a) living in naturalistic social groups on a 375-acre South Carolina b arrier island. Blood and cerebrospinal fluid (CSF) samples were obtain ed during random trappings, and the subjects were located for observat ion by radio telemetry. Quantitative behavioral samples totaling 203 o bservation hours were taken during two mating seasons (September throu gh January) in 1994 and 1995. Control observations (65 h) on 13 subjec ts were also taken during the non-mating seasons in 1994 and 1995. The results indicate that CSF 5-hydroxyindoleacetic acid (5-HIAA), CSF te stosterone, and plasma testosterone concentrations increase significan tly during the mating season. During the mating season, there were sig nificant increases in high intensity aggression, law intensity aggress ion, grooming behavior, and heterosexual mounting. In the mating seaso n, CSF 5-HIAA was significantly correlated with several sociosexual be haviors. consorts per hour, heterosexual mounts per hour, and insemina tions per hour. In contrast to previous findings from the non-mating s eason, CSF 5-HIAA was not correlated with any measures of aggression o r sociality, although during consorting, CSF 5-HIAA was positively cor related with grooming. From these findings, we conclude that the lack of correlation between intense and severe aggression and CSF 5-HIAA in the mating season may reflect the use of high intensity aggression in 'normative' male-male competition over access to reproductively activ e females. We also conclude that CNS serotonin turnover is positively correlated with sexual competence, i.e. males with low CSF 5-HIAA conc entrations are less sexually competent than males with higher concentr ations. (C) 1997 Elsevier Science Ireland Ltd.