EFFECTS OF ALTERING TESTOSTERONE IN EARLY INFANCY ON SOCIAL-BEHAVIOR IN CAPTIVE YEARLING RHESUS-MONKEYS

Thirteen male and twenty female rhesus monkeys (Macaca mulatta), aged 9-12 months, living as members of long term captive social groups: wer e observed in order to quantify sex differences in a variety of behavi our patterns. Six males had been treated with a GnRH agonist (Metereli n: M) during their first six postnatal months, in order to block the s urge of testosterone which occurs at this time. Ten females had been t reated with testosterone (T) during their first six months, in order t o mimic the postnatal T surge seen in males. The remaining 7 males and 10 females acted as control subjects. Marked sex differences were mea sured in frequencies of play and socio-sexual behaviour in these juven ile monkeys. However, neither M nor T treatments produced any signific ant changes in frequencies of these behaviour patterns. Although M-tre ated males showed a tendency (p < 0.1) to groom others for longer peri ods than control males, and control females tended to spend more time alone than T-treated females, we were unable to measure any significan t (p < 0.05) effects of either M-or T-treatment upon affiliative behav iour in juvenile rhesus monkeys. We conclude, therefore, that the post natal T surge in male rhesus monkeys does not affect development of se xually dimorphic and associated patterns of behaviour. Presumably, org anisational effects of T upon these behaviour patterns must be complet ed before birth in this species. (C) 1997 Elsevier Science Inc.