Rhinoceroses are large, herbivorous mammals that require a significant and consistent intake of vegetation to maintain their weight. These animals are hindgut fermenters, meaning they gain energy from the fermentation of fibrous plant material within their digestive system. The specific composition of their diet is not uniform across the five species, varying dramatically based on their physical adaptations and the habitats they occupy. This variation allows different rhino species to coexist in diverse ecological niches across Africa and Asia.
The Grazers
The White Rhinoceros (Ceratotherium simum) is the largest of all rhino species and is classified as a pure grazer, relying almost entirely on grasses for its sustenance. This feeding preference is made possible by a broad, straight, square-shaped mouth. This wide lip structure functions much like a lawnmower, allowing the rhino to efficiently crop wide swaths of short grasses close to the ground.
An adult White Rhino may consume up to 120 pounds of plant material in a single day, primarily selecting for nutrient-rich, short-stature grasses. They graze on species such as panic grass, signal grass, and finger grass, which are commonly found in the savannahs and grasslands they inhabit. White Rhinos spend a significant portion of their day actively grazing. Their large size and high-volume diet make them influential components of their ecosystem.
The Browsers
In sharp contrast to their grass-eating relatives, the Black Rhinoceros (Diceros bicornis) possesses a pointed, prehensile upper lip that enables browsing. This physical adaptation allows the rhino to grasp and pluck leaves, twigs, shoots, and fruits from woody plants and thorny shrubs. The Black Rhino’s diet is highly diverse, often including hundreds of different plant species, and is heavily influenced by the season and local availability.
They use their pointed lip to strip foliage from branches, leaving a clean, angular mark on the remaining woody vegetation, similar to a pruning shear. This species prefers certain plants, including thorny acacia species and those from the family Euphorbiaceae. Black Rhinos feed during the cooler hours of dawn and dusk, retreating to rest or wallow during the hottest parts of the day. Their consumption averages around 50 pounds of vegetation daily, focusing on selecting high-quality food.
Diets of the Asian Species
The three Asian rhinoceros species—the Indian, Javan, and Sumatran rhinos—demonstrate a range of feeding habits that often combine both grazing and browsing. The Indian Rhinoceros (Rhinoceros unicornis), also known as the Greater One-Horned Rhino, is considered a mixed feeder, though its diet consists mainly of tall grasses. They supplement their grazing with leaves, fruits, and aquatic plants from the floodplains and swamps they inhabit.
The Javan Rhinoceros (Rhinoceros sondaicus) is primarily a browser that favors young shoots, twigs, foliage, and fallen fruit in the dense, lowland rainforests of its habitat. While they occasionally graze, their feeding is predominantly focused on vegetation above the ground. The Sumatran Rhinoceros (Dicerorhinus sumatrensis), the smallest of all rhinos, is a pure browser focusing on forest undergrowth. This species consumes leaves, saplings, and twigs, and has a fondness for various fruits, such as mangoes and figs, potentially consuming over 100 different plant species.
Water and Mineral Intake
Rhinos require regular access to water and a source of essential minerals to maintain their health. Water consumption frequency varies; the White Rhino can sometimes go four to five days without drinking due to the moisture content of its grass diet. Most rhinos prefer to drink daily, and Black Rhinos need accessible water sources within eight to sixteen kilometers of their feeding areas.
Rhinos often fulfill their mineral requirements by seeking out natural salt licks, which can be found as salty water seepages, mud-volcanoes, or mineral-rich soil. Consuming soil or licking these mineral deposits provides the necessary intake of salts and other micronutrients. The regular use of these licks is important for browsing species like the Sumatran Rhino. Wallowing in mineral-rich mud also serves the dual purpose of cooling the animal and providing a temporary source of absorbed minerals.