Background/Question/Methods Seasonality in rainfall or temperature strongly structures the environments that large mammalian herbivores occupy. Occasionally, individuals migrate to avoid seasonal declines in forage availability and quality but, more often, forage selection is their main tool for navigating vegetation phenology. In African savannas, where more than 25 species of large herbivore species can coexist, seasonal shifts in each species' diet selection are a key facet of resource competition and seasonal switching between grass and non-grass (i.e., mixed feeding) is thought to be an important dietary strategy. Given that both vegetation quality and quantity decline from the wet season to the dry season in African savannas, we hypothesized that the diets of large herbivore communities would be centrifugally organized; their diets would converge on each other in the wet season when forage is abundant and diverge in the dry season when acceptable forage is rare and acceptability differs among species. To test this hypothesis, we evaluated the diet composition of 13 large herbivore species in Gorongosa National Park, Mozambique across five years, three annual collection periods, and more than 1700 dung samples. Results/Conclusions As expected by both general and herbivore-specific foraging theories, large herbivores' diets were more grassy and often more specialized in the wet season. In addition, each population's dietary breadth increased as vegetation quality declined in the dry season. As expected under centrifugal community theory, diet-breadth expansions coincided with between-species niche overlap declines. Moreover, stochastic block models revealed a core-periphery structure in herbivory networks, which was particularly strong in the wet season where just a handful of plant species were responsible for the majority of herbivores' diets. Ultimately, only a small fraction of plant diversity in Gorongosa is heavily utilized by large herbivores highlighting the importance of understanding the dynamics of strongly interacting species.
