Black rhinos consume mainly woody plants and grasses. The grass is generally only eaten when looking for new low-growth but soft grass leaves are deliberately harvested occasionally and may constitute more than 10% of the rainy season diet.
A wide range of ingested during a foraging year, typically 90% of the diet consists of fewer than 20 species. Species of the families Euphorbiaceae and Tiliaceae, and the legume subfamilies Mimosoideae and Papillionoideae are important in the diet of most ecosystems.
Plant species of the genera Euphorbia, Grewia, and Acacia are particularly important and favorite, and Spirostachys and Acalypha are among the genera of Euphorbiaceae consumed. Among the more herbaceous plant forms favorite of black rhinos, Acanthaceae species, Amaranthaceae family, and Malvaceae are strongly favored. Especially the species of Barlaria, Blepharis, Acaranthus, Amaranthus, Cyathula, Hibiscus, Pavonia, Sida and Abutilon.
A wide variety of secondary plant chemicals are found in black rhino species, many of which are potentially harmful. The ability to cope with these chemicals is an interesting feature of their feeding ecology that is not well understood. Black Rhinos produce tannin binding saliva in response to food types rich in tannins.
The large liver also plays an important role in metabolizing a large liver range of chemicals, but they still need to balance their exposure to any a chemical, which seems to limit the consumption of certain types of plant species (also preferred) and diluting this intake with a puff pastry containing different chemicals (ex. Spirostachys africana), on the other hand, in the face of high levels of secondary phytochemistry, tannins come at a cost, increasing the use of minerals (ex. Biomass contains significant levels of secondary chemicals (polyphenols and tannins).
Black rhinos forage within a specific height range, which is less than 2 m. They do, however, push over trees, especially those with a spindly growth form, to access browse above 2 m. High branches can also be pulled or broken down to feed on.
Because smaller size classes of most woody species are preferred, a growth of tall grass and a mainsail (common in higher-rainfall ecosystems) can substantially interfere with feeding. This can lead to rhinos avoiding areas of long grass altogether or feeding on less-preferred, taller plants instead.
Black Rhinos often feed on burnt plants and coppicing browse in burned areas, preferring areas with intermediate intensity burns. Increasing attention is being paid to the negative impact that other potentially competing browsers may have or have had on Black Rhinos’ habitat and carrying capacity.