Population Viability Analysis of the Nigeria-Cameroon Chimpanzee (Pan troglodytes ellioti) in Cross River State, South South Nigeria

This study conducts a population viability analysis (PVA) for the Nigeria-Cameroon chimpanzee Pan troglodytes ellioti in the forested landscapes of Cross River State, South South Nigeria. Pan troglodytes ellioti is the most critically endangered chimpanzee subspecies, with fewer than 6,000 individuals estimated globally, yet formal quantitative modelling of population persistence under alternative scenarios has not been conducted for Nigerian subpopulations. Demographic parameters including age-specific survival rates, fecundity, and adult sex ratio were derived from long-term monitoring data from Afi Mountain Wildlife Sanctuary and published literature on comparable populations. Habitat connectivity parameters were derived from satellite image analysis of forest cover change from 2015 to 2023. Stochastic demographic simulations were run in Vortex software under six scenarios representing different levels of habitat loss and hunting pressure over a 100-year projection period. Under the baseline current-conditions scenario, the probability of extinction within 100 years was 48 percent. Immediate cessation of hunting reduced extinction probability to 11 percent. Combined hunting cessation and habitat corridor creation reduced it to 6 percent. Inbreeding depression emerged as a significant driver of decline in scenarios with isolated subpopulations. The study provides scenario-specific extinction risk estimates directly applicable to the Cross River State Government's Pan troglodytes ellioti Action Plan and identifies anti-poaching and corridor restoration as the highest-return conservation investments for chimpanzee persistence. Keywords: population viability analysis, Pan troglodytes ellioti, chimpanzee, Cross River State, extinction risk.