An unparalleled abundance and diversity of large herbivores maintain an open structure of these tree-grass ecosystems in the seasonal tropics of Africa and south Asia. Large herbivores are pivotal in maintaining short rhizomatous and tussock grasses, limiting recruitment of trees, cycling nutrients, sustaining complex food webs of invertebrate detritivores and diverse assemblages of mammalian and avian predators and scavengers. Seasonally high productivity coincides with the summer rainy season. Fires occur in some years, but are less influential than herbivores on ecosystem function. Trees and grasses have adaptations to seasonal drought and heavy browsing, such as rhizomes and stolons that allow grasses to spread under grazing pressure.