Positive population trends among meso- and megaherbivores follow intensive conservation efforts in Volcanoes National Park, Rwanda

Abstract

It is unclear whether the remarkable recovery of mountain gorillas Gorilla beringei beringei in the Virunga Mountains, East Africa, that followed decades of intensive conservation efforts, is indicative of positive trends in abundance and distribution of other large mammals (meso- and megaherbivores). Positive population trends are particularly relevant for globally threatened elephants Loxodonta sp., as conservation and research efforts have predominantly focused on populations that range in lowland savanna ecosystems rather than the smaller but ecologically and genetically unique populations found in the Virunga montane ecosystems. We used marked pellet group counts in dung clearance plots to determine the density/abundance and distribution of three mesoherbivores (buffalo, black-fronted duiker, bushbuck) and one megaherbivore (elephant) in Volcanoes National Park (VNP; covering part of the Virunga Mountains), Rwanda, in July–September 2008 and 2021. We estimated that elephants and duiker populations saw a minor increase between 2008 and 2021 while densities of buffalo and bushbuck increased substantially over the course of the past decade. We also found no evidence of substantial distributional shifts for elephants but observed increases in densities of the other species in the southwestern parts of the VNP. Overall, density estimates for all species were much higher in both 2008 and 2021 than in a previous survey in 2004, which suggests that meso- and megaherbivores have largely recovered from a steep decline in numbers towards the end of the 20th century, possibly benefitting from the same protection efforts that benefitted mountain gorillas.