Refining the matrix population model of Balinese macaques under birth control: current outcomes and future projections

Details

Supervisors

Schtickzelle, Nicolas ; Brotcorne, Fany

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie

Abstract

Following environment disturbances such as urbanisation, agriculture expansion and deforestation, the number of contact zones between humans and wildlife is constantly increasing. Particularly in tropical zones, many primate populations live in anthropogenic habitats under “co-ecologies” with humans, which forces them to adapt to novel environments. The long-tailed macaque (Macaca fascicularis) population of the Ubud Monkey Forest in Bali (Indonesia) coexists with humans in such an interface, where it is daily provisioned and without any predation pressure. In addition to their noteworthy capacity of adaptation to environmental changes, under such conditions, Ubud macaques have higher survival chances and fertility and lower mortality rates, in a decreasing habitat area. As a result, the population faces a phenomenon of overcrowding, endangering both local communities and monkeys. In 2017, population viability analyses (PVA) including a matrix population model were developed in order to calibrate a sterilisation program (via female tubectomy). The latter aimed at controlling the population growth by holding it back at the equilibrium and therefore mitigating the risks linked to the human-macaque conflicts. Several sterilisation campaigns took place between 2017 and 2019 to reach the initial sterilisation rate fixed by the matrix population model (i.e. 52% of reproductive females). This master's thesis aims at refining the matrix population model established in 2017 by: (i) including the updated data collected between 2017 and 2020, (ii) adding the data related to sterilisations and some behavioural parameters of females (hierarchical rank and maternal experience) supposed to impact their reproductive success and therefore the population demography. The aim was to build new projections of the population trends under several scenarios (i.e. epidemic outbreaks). An improved matrix model was built based on the previous one, first theoretically, by including further parameters (species biology, data and field reality, …) and finally through statistical analyses based on the Akaike information criterion (AIC) using SAS software. The final model selected is not much more complex than the previous one since only the data related to the sterilisations was inserted. Projections of the population trends over 25 years indicate that further regular sterilisation efforts should be undertaken to manage the population and maintain it at the equilibrium, thereby mitigating the problems related to the overcrowding situation.