Effects of medroxyprogesterone acetate on socio-sexual behavior of stumptail macaques

Two studies assessed (1) the effect of medroxyprogesterone acetate (MPA), Depo-Provera, on socio-sexual behaviors, and (2) the interaction between socio-environmental conditions and MPA treatment effects. Study One utilized two males and eight female members of a semi-free-ranging island colony. Females received 30 or 100 MPA IM or were untreated. Study Two used three laboratory-housed pairs of tubal-ligated females, observed during 30 min behavior tests with one of three males. Sexually preferred females received 30 mg MPA IM. Semi-free-ranging treated females received fewer ejaculations than untreated females and did not copulate for up to 68 days post-treatment. Rates of grooming were not affected. In the laboratory tests, mean rates of ejaculations per test were reduced for treated females but increased for untreated females, and untreated females groomed males more than did treated females. Contrary to previous studies, these results suggest that stumptail macaque sexual behavior can be influenced by hormones but this influence is modulated by socio-environmental factors.