Will the Nigeria-Cameroon Chimpanzee Go Extinct? Models Derived from Intake Rates of Ape Sanctuaries

Abstract

All great ape taxa are considered endangered due to a combination of habitat loss, hunting, disease outbreaks and human population increase. The bush-meat trade is thought to be the biggest threat to the survival of chimpanzees, bonobos and gorillas. However, assessments of the reduction of wild populations are notoriously unreliable since they are mostly based on indirect evidence such as brief surveys of markets and interviews with hunters. We use a direct approach and measure annual loss from the wild through intake rates of sanctuaries in Africa which currently hold close to 1000 apes. From these, we calculate loss to the wild populations by relating arrivals into sanctuaries to the proportions of infants in wild groups, hunting strategies, and the likelihood that captured babies make it to a sanctuary. We focus on the most endangered chimpanzee subspecies, Pan trog- lodytes vellerosus, found in eastern Nigeria / western Cameroon. Our calculations, based on intake rates since 1986 into four sanctuaries in Cameroon and Nigeria, suggest that current rates of hunting are 2 – 13 times higher than sustainable rates. Moreover, VORTEX – a population viability analysis tool – predicts that this chimpanzee subspecies will go extinct in as little as 20 years. The dramatic results emphasise the need for immediate conservation measures. Ape sanctuaries are, at times, considered to be a waste of resources, which could be better diverted to habi- tat protection. However, it is extremely unlikely that hunting pressure can be sig- nificantly reduced, and many local ape populations are already effectively extinct. Sanctuaries will therefore play an increasingly important role as ape conservation tools, if only for the fact that they may, in a couple of decades, harbour more apes than survive in the wild. We propose to apply our method of measuring extinction risk to other taxa of apes across Africa and Asia.