CORRELATION OF CSF 5-HIAA CONCENTRATION WITH SOCIALITY AND THE TIMINGOF EMIGRATION IN FREE-RANGING PRIMATES

Objective: The purpose of this study was to examine the relationship b etween behavior and serotonin in nonhuman primates. Method: During a r outine capture and medical examination, 26 adolescent male rhesus maca ques (Macaca mulatta) were selected as subjects from a free-ranging po pulation of 4,500 rhesus monkeys inhabiting a 475-acre sea island. Blo od samples (N=23) and CSF samples (N=22) were obtained, and each subje ct was fitted with a radio transmitter collar for rapid location. The subjects were released into their social groups, and quantitative beha vioral observations were made over a 3-month period. Results: CSF 5-hy droxyindoleacetic acid (5-HIAA) concentration was positively correlate d with three measures of sociality: 1) total time spent grooming other s, 2) total time spent in close proximity to other group members, and 3) mean number of neighbors within a 5-m radius. In addition, CSF 5-HI AA concentration was positively correlated with age at emigration from the natal group (in months). Conclusions: In adolescent male rhesus m acaques living in naturalistic settings, CSF 5-HIAA concentration is p ositively correlated with affiliative sociality. Rhesus males with low CSF 5-HIAA concentrations exhibit less social competence and emigrate from their social groups at a younger age than do males with higher c oncentrations of CSF 5-HIAA.