Passive Acoustic Monitoring of Cercopithecus nictitans in Ivindo National Park

Abstract

Faunal degradation, characterized by the loss of species from animal communities, threatens ecosystems functions and services. In Gabon's Ivindo National Park, bushmeat has long sustained local communities, underscoring the balance needed in human-wildlife interactions for effective conservation. Defaunation gradients in Ivindo National Park are previously shown to be influenced by hunting. We utilized Passive Acoustic Monitoring (PAM), a cost-efficient alternative to traditional transect surveys that avoids effects of observer presence and bias in the field, to evaluate the impact of anthropogenic activity on Putty-nosed monkey (Cercopithecus nictitans), a commonly hunted arboreal primate species, relative abundance. Acoustic Recording Units (ARUs) were placed in five transects, each four km long, radiating from the Ivindo River. ARUs were also placed at five Longhi Rouge trees (Chrysophyllum lacourtianum). ARUs were spaced two km apart to assure independent detections. Our study resulted in 86,799 minutes of recording from 18 PAM sites. We found that encounter rates of Putty-nosed monkeys significantly increase with distance from the Ivindo River and the national road, and that Putty-nosed monkeys visit Longhi Rouge trees in areas close to the river. The need for collaborative conservation efforts that integrate indigenous knowledge and empower local communities is necessary for successful conservation projects and sustainable development. Using PAM offers the possibility of training species-specific detection models that can assist in long-term monitoring of vocalizing wildlife species.