Demographic trends and Streptococcus outbreaks in a synanthropic population of macaques (Macaca fascicularis), Bali (Indonesia)

The sympatric relationship between humans and primates is a contemporary widespread phenomenon. Several primate species are capable for exploiting human-modified habitats in association with people, but the most successful species in South-east Asia is probably the long-tailed macaque (M. fascicularis). The low predation pressures in zones of interface and the inclusion of human food in macaques’ diet can lead to local overpopulations. On the other hand, the risk of epidemic disease is simultaneously increased by the high primate density and the proximity with human vectors. Data presented here represent 25 years-population dynamics of a long term commensal-living population of macaques in Ubud Monkey Forest (Indonesia). This population experienced a dramatic growth with an 11% annual increase rate. In June 2012, we counted 615 individuals divided in 5 groups with a very high density of 61 macaques per hectare. However, two Streptococcus outbreaks have also been reported over the same 25 years period, temporarily limiting the steep positive demographic trend of this population. The last epidemic event in July 2012 resulted in a 14% mortality affecting 3 out of 5 groups of the population. Besides the anthropic factors promoting population growth, epidemic diseases play a significant role in shaping the dynamics of this synanthropic population and could have important implications in the future both in terms of local management and local conservation status.