The generality of cryptic dietary niche differences in diverse large-herbivore assemblages

The diversity of ungulates in African savannas has inspired generations of biologists to investigate how similar species coexist, which requires that each be limited by different factors. Resource partitioning is key to understanding this diversity, but prevailing theories of competition and coexistence disregard the taxonomic identity of food items. Using high-resolution data on thousands of large-herbivore diets from 10 savannas, we identify several apparent generalities. Sympatric herbivore species eat different plants in differing proportions, and variation in the strength of these differences supports the hypothesis that interspecific competition and species' traits interact to shape diet composition and food web topology. We conclude that partitioning of food plant species, while difficult to detect, contributes to the niche differences that stabilize coexistence.