Impact of gun-hunting on monkey species and implications for primate conservation on Bioko Island, Equatorial Guinea

Bushmeat hunting is among the principal threats to larger-bodied vertebrate species, such as primates, in central Africa. However, species vary in their response to differing levels of hunting intensity, making it difficult to not only quantify the effect hunting has on wild populations, but also to plan for effective conservation interventions. In order to investigate the impact of hunting on primates on Bioko Island, Equatorial Guinea, we collected data on primate abundance and hunting intensity across three areas in the Gran Caldera Scientific Reserve (GCSR) via reconnaissance surveys. We assessed how the relative abundance and proportional representation of Bioko's seven diurnal primate species varied among the different sites and in relation to hunting intensity. Overall primate species richness and abundance were highest in areas where gun hunting was minimal, but both measures declined with increasing evidence of gun hunting. Two species of primates, Cercopithecus erythrotis and Cercopithecus nictitans, were relatively tolerant of heavy hunting, but all other species were considered vulnerable. Procolobus pennantii, a species endemic to Bioko, exhibited the highest vulnerability, and its range appears restricted to a very limited area in the southwest of the GCSR. Our analyses indicate that hunting on Bioko is a strong contributor to current patterns of primate abundance and diversity, and suggest that hunting may be driving Bioko's most threatened primates (e.g., P. pennantii) towards extinction. These results highlight the need for rapid intervention on Bioko in order to safeguard the future of its unique primates.