Behavioural responses of long-tailed macaques (Macaca fascicularis) to environmental fluctuations: a preliminary study on Belitung Island, Indonesia

Human presence and climate constraints shaped the primate adaptation to employ behavioural strategies. In this study, we examined the relationship between the food environment (human presence and microclimate) and behavioural responses of long-tailed macaques ( Macaca fascicularis ) in secondary and mangrove forests of coastal habitats on Belitung Island, Indonesia, over six months (March-August 2023), with 509 h of total observations. The macaques were mainly frugivorous, but a small amount of human food consumption persisted in response to the presence of humans. The macaques spent more time resting and autogrooming, decreased both moving and feeding, fed more on human food, reduced mature fruit consumption, and decreased home range sizes when visitors were more present. Furthermore, higher humidity levels decreased feeding activity and reduced the consumption of mature fruit, seed, other plant matters, and water intake in macaques, whereas the frequency of their autogrooming and canopy usage increased. Rainfall and temperature did not substantially exhibit relationship with behavioural ecology of macaques, which supported other long-tailed macaque responses from several regional sites. The macaques appeared to have adapted to human presence and microclimate by employing an energy-minimizing strategy, i.e., using the least costly energy in activity and ranging behaviour in taking human resources, and shifting activity, diet, and particular strata as microhabitat selection during humidity stress. Overall, macaques exhibited a generalist primate species where their behaviour and dietary adaptation allowed them to address anthropogenic and microclimate pressure. Our findings provided valuable reports and essential data for developing conservation programs and strategies, particularly concerning the impacts of human presence and climate change on macaque behaviour.