Contrasting use of fruit trees by sympatric primate groups differing in habituation status

While humans have been considered as super predators in diverse ecosystems, many animals are habituated to humans in research or tourist sites, releasing them from the fear of humans. However, the impacts of habituation on interspecific competition remain poorly understood. We studied competition for fruits of Choerospondias axillaris between sympatric langurs (Trachypithecus crepusculus) and gibbons (Nomascus concolor) with different habituation statuses using satellite positioning collars, full-day follows, and canopy camera traps. In areas where both species were habituated, 99.4% of C. axillaris fruits were consumed by langurs because langurs always started feeding on the fruit much earlier in the season and had larger feeding parties and longer feeding bouts. In contrast, in areas where langurs were not habituated to humans, only 20.7% of C. axillaris fruits were consumed by langurs because the unhabituated langur group reduced access to fruit trees mainly located in the lowland area outside the reserve. These findings identify a context-specific case in which human-associated risk altered access to a shared seasonal important resource among sympatric primates, with implications for understanding how human presence can modify species interactions.