Effects of chronic melengestrol acetate contraceptive treatment on perineal tumescence,body weight,and sociosexual behavior of hamadryas baboons (Papio hamadryas)

Melengestrol acetate (MGA) subcutaneous implants were used in seven adult female Hamadryas baboons to study the effects of chronic progestin administration on perineal swelling, behavior, and weight gain. At the dose level used (≥8 mg/kg body weight), cycles of perineal tumescence ceased and swellings subsided. Social dynamics were not significantly altered during treatment, and only minor changes in agonistic interactions were noted following implant removal. Body weight increased by 17.3–47.6% during treatment despite decreased time spent foraging. This paradox may be explained by 1) foraging time not necessarily corresponding to total intake and 2) the nonsignificant trend toward lower levels of activity during treatment. Treatment with MGA can be recommended based on its ability to suppress ovarian cyclicity without causing social disruption. However, because this and other progestins stimulate weight gain, their use is contraindicated in overweight or obese animals. © 1995 Wiley-Liss, Inc.