Rhinoceroses eat as many as 220 different species of grasses, herbs and woody plants as part of their regular diet. Black rhinos eat mostly trees and bushes, while white rhinos graze on grasses lower to the ground.
Long grasses constitute as much as 40 percent of the black rhino's diet, but this species normally eats leaves, twigs and branches. White rhinos exclusively eat grass, which is why their heads appear lower to the ground as they walk. The main difference between the species is the shape of the animals' mouths.
Black rhinos have pointed upper lips, while white rhinos have square lips. The pointed lips are ideal for plucking leaves from branches.
Digestion occurs towards the back of the rhinos' digestive tract. Bacteria ferment plant material in the stomach in the same way as horses and zebras. A single rhinoceros produces up to 50 pounds of dung per day because of its voracious appetite. Rhinos weigh up to 3,800 pounds.
Rhinos handle droughts better than other African animals. The giants' bodies are not susceptible to poisonous tannins in plants, substances that often increase during dry seasons. A rhinoceros may go 5 days without drinking water if its diet consists of plants with a lot of water content. In the wild, a rhino is usually within one walking day of a water source.