Long-term changes in dung beetle community structure in the Serengeti Ecosystem

Dung beetles (Scarabaeinae) are key drivers of ecosystem functioning and are widely recognised as sensitive indicators of environmental change. However, long-term assessments of dung beetle community dynamics in African savannas remain scarce, limiting our understanding of how communities change through time and the environmental factors that drive these changes. Understanding temporal patterns in dung beetle assemblages is important for assessing their stability and resilience and predicting their responses to future climatic variability. We investigated multi-decadal changes in dung beetle communities within the Serengeti Ecosystem by comparing historical surveys conducted in 1991-1992 with contemporary surveys from 2024. Although our results revealed that species richness and diversity in 2024 were broadly similar to those recorded in 1991, community composition differed significantly among survey years, with only 45% of species occurring consistently across all years, and 21.7% occurring exclusively in 2024. These compositional shifts were accompanied by marked changes in functional group structure, including a dramatic decline in large rollers, which decreased from 35.3% of individuals in 1991 to just 0.6% in 2024, and increases in slow-burying tunnellers and small rollers. Community body-size structure also shifted toward smaller-bodied beetles, with a pronounced reduction in large-bodied individuals and a corresponding decline in dung beetle biomass by 2024. Together, these findings indicate that long-term ecological change was more evident in species identities, functional composition, and body-size structure. Community compositional changes were associated with temporal variation in rainfall, suggesting that climatic conditions have restructured dung beetle assemblages despite the Serengeti ecosystem's protected status. Our findings demonstrate that dung beetle communities in the Serengeti Ecosystem are highly dynamic across decadal timescales and emphasise the value of integrating taxonomic, functional, and biomass-based approaches in long-term biodiversity monitoring.