Habitat heterogeneity and functional adaptive resources for wild and domestic herbivores in Okavango Delta, Botswana

Abstract

Abstract Functional adaptive resources (FARs) for herbivores are distributed along soil moisture gradients from wetlands to drylands. They are critical for enabling wild and domestic herbivores to adapt spatially to strong variations in forage quantity and quality in African savannas. We studied how FARs for large herbivores are distributed across the moisture/flooding gradients from extensive woodland systems (not flooded) through different levels of flooding in an adjacent extensive wetland system of the northeastern Okavango Delta Panhandle, Botswana. Vegetation composition was strongly differentiated along the flooding gradient. Woodlands grasses supported higher protein and minerals (except sodium) during the wet season than grasses in flooded habitats. Grasses in shallow-flooded habitats supported the highest sodium content, and grasses in deep-flooded habitats had the highest protein, biomass and greenness during the dry season. Access to wetlands that support high-biomass, protein-rich grasses during the dry season allowed free-ranging cattle at Eretsha to maintain significantly better body condition during a drought year than cattle without access to these habitats. Our findings demonstrate the critical importance of extensive landscapes providing access for herbivores (wild and domestic) to both wetlands and drylands in African savannas. This has large implications for designing protected areas and for pastoralists’ livelihoods where landscapes are being rapidly fragmented by fencing and land use change.