Acoustic Monitoring and Population Trends of Nocturnal Primates in Okomu National Park, Edo State, South South Nigeria

This study applies passive acoustic monitoring (PAM) to detect and assess population trends of nocturnal primates in Okomu National Park, Edo State, South South Nigeria. Okomu National Park is a critical forest habitat in the South South zone harbouring Nigeria's only confirmed population of red colobus and rare nocturnal primates including potto and Demidoff's dwarf galago, yet nocturnal primate populations have never been formally monitored. Autonomous recording units (ARUs) were deployed at 20 stations for 12 consecutive months. Automated species recognition algorithms trained on West African primate call libraries were applied, with manual verification of detections. Occupancy modelling estimated detection probabilities and site occupancy for each species. Community composition was compared across edge and interior forest stations. Four nocturnal primate species were confirmed acoustically: potto Perodicticus potto, Demidoff's dwarf galago Galagoides demidovii, Western needle-clawed galago Euoticus elegantulus, and the pygmy scaly-tailed squirrel (confirmed nocturnal vocaliser). Occupancy was significantly lower at edge stations for all four species. Seasonal call rate analysis indicated that breeding vocalisation peaked in November to December for all species. Demidoff's dwarf galago showed the highest occupancy (0.84) and potto the lowest (0.42), suggesting differential sensitivity to the park's fragmented interior quality. The study establishes the first PAM-based baseline for nocturnal primate monitoring in Okomu National Park and provides acoustic identification protocols for future monitoring. Keywords: acoustic monitoring, nocturnal primates, Okomu National Park, Edo State, galago.