Unpaved road verges are attractive habitats for dung beetles (Coleoptera: Scarabaeidae) in a plantation forestry-grassland mosaic

Abstract

Roads have direct and indirect impacts on biodiversity, although the impacts on insects are not yet fully understood. In a plantation forestry-dominated landscape in South Africa, where natural grasslands make up ecological networks of conservation corridors among plantation compartments, we investigated the impact of maintained unpaved roads and unmanaged tracks on dung beetles. We show that these two types of roads have little impact on dung beetle species richness and assemblage structure, indicating that road verges are attractive habitats for dung beetles. Yet, nocturnal dung beetle abundance increased with distance away from roads, suggesting that areas farther away from roads are important to maintain their population sizes. Vegetation characteristics, especially total cover by grasses and overall vegetation height, were important drivers of dung beetles, yet substrate characteristics were unimportant. With vegetation characteristics being related to road maintenance, roads in the landscape have an indirect impact on dung beetle species richness, abundance, and assemblage composition, rather than a direct impact. Road construction in production landscapes is unavoidable, and their edges are attractive to dung beetles. This means that road users should avoid unnecessary road killings by strictly keeping to the road tracks. Habitat heterogeneity across the overall landscape should be encouraged to minimize current and future impacts of roads on dung beetles. The expansion of road networks, or the maintenance of existing road networks, should be done cautiously so as to promote habitat heterogeneity which is important for maintaining regional dung beetle diversity patterns.