Anthropogenic disturbance and competitive avoidance shape the coexistence pattern of macaque species in tropical forests

The factors that enable the coexistence of closely related species remain a major question in ecology, particularly in human-disturbed habitats. The effects of anthropogenic disturbance and interspecific competition can exacerbate the decline in populations of competing species. The adoption of different strategies in responding to anthropogenic disturbances and competitive avoidances may create opportunities for competing species to coexist. However, few studies have explored how disturbance and competition interact to shape species coexistence. In this study, we conducted long-term and large-scale camera trap surveys comprising 540 sampling sites from 2017 to 2021 at Xishuangbanna, southwestern China, and deployed a spatiotemporal analysis framework to determine the effect of anthropogenic disturbances and competitive avoidances on the coexistence of three sympatric macaque species: Assamese macaque (Macaca assamensis; MA), northern pig-tailed macaque (M. leonina; ML), and rhesus macaque (M. mulatta; MM). Macaque species exhibited diverse responses to different types of anthropogenic disturbances. The occurrence probability of MM was positively associated with distance to road and relative abundance of human occurrence, and negatively associated with distance to cropland, which reduces the likelihood of sympatry between MM and the other two species due to their opposing responses to road, cropland, and human occurrence. Conversely, the similar responses to road and cropland increase the sympatry between MA and ML. Three macaque species did not avoid each other through shifting space use or their overall daily activity pattern. However, they delayed using the shared site after other species used it to avoid confrontation. We provide evidence that (1) the spatial co-occurrence pattern of sympatric macaque species was determined by anthropogenic disturbances rather than by competitive spatial avoidance and (2) fine-scale temporary avoidance is the strategy to alleviate their interspecific competition. These results enhance our understanding of the underlying mechanisms leading to species coexistence of nonhuman primates in human-disturbed habitats.