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Savannas are highly dynamic, and reactions to particular events, such as fire or temporarY drought, are transmitted through the ecosystem by interactions between different components. Indigenous herbivores respond to spatial and temporal variations in the vegetation by selectivity of forage on scales from landscape to a single bite, and by demographic changes. Herbivory itself induces changes in plants and vegetation, which in turn may promote or deter further foraging. Domestic herbivores are less mobile than many wild species, impeding large-scale selectivity, and are kept at less variable and usually higher densities, which prevents small-scale selectivity. Livestock numbers decrease following fodder shortage, only after a considerable timelag. Herbivores may interact with competitive patterns between woody and herbaceous vegetation as well as with fire regimes, and may thus be involved in large-scale physiognomic dynamics of savannas.