Abstract: The Bengal Slow Loris （Nycticebus bengalensis） and the Northern Pygmy Loris （Xanthonycticebus intermedius） are respectively endangered and critically endangered nocturnal primates in China. Owing to their cryptic ecological habits, empirical data on their spatial distribution and coexistence patterns in the wild have long been insufficient. Using camera-trapping technology, this study conducted camera-trap monitoring in the Maguan Gulinqing Provincial Nature Reserve, Yunnan Province, aiming to obtain video evidence of their sympatric coexistence. The monitoring results confirmed that both species were successfully detected, with the nearest effective recording sites approximately 110 m apart in straight-line distance, confirming this area as a sympatric zone for the two species. The Northern Pygmy Loris exhibited a significantly higher trap rate and recording frequency than the Bengal Slow Loris, demonstrating an absolute numerical dominance, implying potential interspecific competition and niche differentiation. Notably, frequent activities of the Northern Pygmy Loris were recorded at elevations of approximately 1600－1700 m, challenging the traditional paradigm that this species is restricted to low-altitude rainforests below 500 m. This suggested that the species might possess the potential to adapt to cold, high-altitude environments by virtue of physiological plasticity, such as a low metabolic rate and heterothermy. Methodologically, canopy-level camera placement and color video recording effectively overcame the monitoring blind spots and identification difficulties associated with nocturnal small primates. Based on these findings, it is recommended that conservation efforts focus on key high-altitude habitats and maintain canopy connectivity to facilitate the population recovery of these threatened primates.

Key words: Nycticebus bengalensis;Xanthonycticebus intermedius, sympatric distribution, camera-trapping, high-altitude adaptation