Demographic changes and behavioural ecology of a commensal long-tailed macaque population at Padangtegal, Bali (Indonesia)

The current anthropic pressures lead to a growth of the commensalism phenomenon with primates and humans interacting and competing for space and food. As these situations generate inter-specific conflicts, an extensive analysis seems essential for primate conservation issues. Bali (Indonesia) is characterized by a high density of long-tailed macaques (Macaca fascicularis) living in association with humans. The macaque population of the Padangtegal Monkey Forest (Ubud) has been the focus of successive studies since 1986 (Wheatley, 1986; Fuentes et al., 2007). Here, we present updated data (September-December 2009) on demography, activity budget and diet of this population while analyzing variations over time. The macaques at Padangtegal showed a substantial population growth over the last thirty years (34% average growth every 6 years). In 2009, we listed 498 individuals split in 5 groups with an average adult sex ratio of 1:4.5. The home range size also increased over time (7ha in 1986 vs. 30ha in 2009) but was finally limited by surrounded human infrastructures. Consequently, the population density doubled in the course of the last 8 years and counted 16.6 macaques per hectare in 2009. On the other hand, the activity budget pattern appeared quite stable over time with a large proportion of time spent inactive and socializing and a relatively small proportion of time spent in feeding activities. This activity pattern is characteristic of provisioned primate populations. Finally, the diet composition slightly varied over time except for the radical decrease of provisioned carbohydrate-rich food proportions, following some management decisions. Macaques at Padangtegal thus show some stability in their behavioural ecology despite considerable changes in demography. Nevertheless, these positive population trends do not protect macaques from some long term risks tied to commensalism, such as inbreeding depression and increased probability of disease transmission.