Decade-long monitoring in Lomako-Yokokala Faunal Reserve, DRC: Impacts of ranger patrols on mammal population status

Protected areas are crucial for biodiversity conservation, and effective monitoring of animal population trends is critical for proper management. However, sustaining long-term monitoring remains challenging. In 2023, we conducted a reserve-wide survey in the Lomako-Yokokala Faunal Reserve, Democratic Republic of Congo, to evaluate mammal population change over the past decade. This reserve, a Bonobo (Pan paniscus) study site since 1974, has been managed with ranger patrols since 2006. To ensure comparability, we replicated the methods of a 2010 survey, using index sampling and reconnaissance methods – cost-effective approaches for rainforest mammal monitoring. Encounter rates for most target species increased since 2010, with one monkey and four duiker species showing at least fourfold rises, while hunting signs declined. Some large mammals displayed uneven distributions, reflecting historical hunting pressures during periods of political instability, whereas others showed recovery even in areas with poaching signs. Although detectability differences between surveys cannot be excluded, the observed increase in encounter rate indicates the effectiveness of ranger patrols. Further research into detectability factors and thresholds for significant changes will enhance the reliability of indices as long-term monitoring tools in tropical forests.