Investigating Potential Effects of the Contraceptive Implanon on the Behavior of Free-Ranging Adult Female Barbary Macaques.

In recent years, the use of hormonal contraception in captive, free-ranging, and wild mammal populations has increased, but the effects on these nonhuman animals' behavior and the associated welfare impacts remain poorly understood. This study of free-ranging adult female Barbary macaques (Macaca sylvanus) at Trentham Monkey Forest compared females implanted with the progestin-only contraceptive Implanon to those not receiving contraception. Females with contraceptive implants had higher rates of self-scratching and spent more time self-grooming (2 behavioral indexes of anxiety) than those without implants. They also directed more aggression at others, spent more time receiving grooming and traveling, and spent less time giving grooming and resting. No significant differences between the 2 groups of females were seen for time spent foraging. These results suggest that Implanon had a number of effects on Barbary macaques, although these need to be considered in light of the significant benefits afforded by the use of this contraceptive. The findings of this study provide important information to those evaluating the relative welfare costs and benefits of alternative methods of population control in this and other species.