Population dynamics and ranging behaviour of a highly provisioned population of Macaca fascicularis in Bali: implications for management

In response to the global landscape anthropization caused by the extensive urbanization and the recruitment of forestlands for cropping, the primate-human commensalism is growing as well as the related interspecific conflict. In zones of interface, humans and primates are sympatric and compete for food and spatial resources. Today, we still poorly know the proportion of synanthrope primates and the impact of anthropic pressures. We present here data on 25 years-population dynamics and ranging behaviour of a long-term commensal-living population of long-tail macaques (Macaca fascicularis) in Ubud Monkey Forest, Bali (Indonesia). This population has experienced a dramatic growth over 25 years with an annual increase rate of 11%. In 2011, we counted 614 macaques split in 5 social groups and using an overall home range of 10ha with a 2.41ha core area centred on human provisioning places. We derived a very high population density of 61 macaques per hectare and concluded that this site is overpopulated. Moreover, the conflict between humans and macaques is increasing and requires specific management. As the natural food supply is low in Ubud Monkey Forest, we assume that the high carrying capacity of the site mainly depends on the artificial food supply. The abundance and the quality of artificial food may be the major factor determining such a high population density. The low predation pressure and the habitat compression by destruction of adjacent forests could also influence the positive demographic trend. As a tentative program of population control, we suggest both to lower the caloric content of the food provisioned to macaques and to conduct a sterilization programme. This strategy aims at reducing the conflict with humans and at promoting a sustainable coexistence by reducing birth rates and limiting the macaques’ population growth.