Primate Abundance in an Unhunted Region of the Northern Peruvian Amazon and the Influence of Seismic Oil Exploration

The western Amazon, a relatively remote and unstudied region, is experiencing unprecedented levels of oil and gas exploration. Despite the widespread use of seismic reflection technology for oil and gas exploration, no studies have investigated the response of primate populations to this disturbance in the Amazon. We conducted distance sampling along transects in pristine, unhunted lowland rain forest inside a large oil concession (Block 39) in the northern Peruvian Amazon with ongoing 2D seismic exploration. We aimed to investigate seismic exploration effects on local primate abundance, with a particular focus on the region’s most endangered primates, lowland woolly monkeys (Lagothrix poeppigii) and white-bellied spider monkeys (Ateles belzebuth). We sampled transects before the arrival of exploration crews (control) and during the seismic operation (disturbance) and compared primate counts using mixed-effect models. We confirmed the presence of nine species of primates along sampled transects. Abundance of primate groups (species pooled) was not different between the control and disturbance period, yet abundance of primate individuals was significantly lower in the disturbance period. Although we encountered groups of Ateles belzebuth equally often during the control and disturbance periods, overall counts of individuals of this species were lower during the disturbance period owing to lower subgroup sizes. This suggests this species may have responded, at least temporarily, with localized spatial avoidance, and that it may be particularly sensitive to human disturbance regardless of hunting pressure. Our overall density estimate for Lagothrix poeppigii (30.6/km2) approaches the highest reported for the species. Although the relatively temporary nature of 2D seismic exploration may limit its effect on primate species, our data indicate some species may respond more negatively than others.