Mémoire
| Résumé : | Today, human population growth and massive land conversion are major threats for primate conservation. Some highly flexible species, such as long-tailed macaques (Macaca fascicularis), are however more armed to thrive and even flourish in anthropogenic habitats.Due to a lack of predators and food abundance, some populations grow in an uncontrolled way, leading to stressed human-primate conflicts. Population control is therefore sometimes necessary to reduce these conflicts and promote a sustainable coexistence. Whereas birth control is an increasingly used strategy to control primate population, very few data are available on its efficiency and consequences. Tubectomy is a surgical sterilization procedure that, unlike ovariectomy, does not alter the secretion of sex steroid hormones. However, little is known about the long-term impacts of the permanent absence of new infants on the behavior of sterilized females, and the related social costs. We investigated these questions in the long-tailed macaque population of the Ubud Monkey Forest, in Bali. We also monitored stress levels in these sterilized females in order to assess welfare implications. We analyzed a three-year behavioral dataset (2017-2019) using two different analytic approaches: a transversal approach (we worked on the data collected in 2018 to compare 20 sterilized females with 22 control females, and on the data collected in 2019 to compare 38 sterilized females with 26 control females) and a longitudinal approach (a within-subject follow-up of 19 females over 3 years following their sterilization). We observed that tubectomy moderately impacts behaviors of sterilized females. They were more active than control females, engaging less in resting, and more in sexual and agonistic activities. Beside these variations in global activities, a fine-grained analysis focused on female network revealed that sterilization did not modify the social status of the treated females: they were not less groomed by or less in contact with other females than control females. Consistently, we found no clear evidence that sterilization increases stress levels in treated females. Further longer-term studies with larger dataset including additional confounding factors such as dominance rank and kinship, are necessary to draw neat conclusions on the effect of birth control on macaque social dynamics. |
