September 22 is world rhino day. Learn more about this unique animal whose existence is under threat. The name rhinoceros comes from the Greek words rhis (nose) and keros ( horn).Among the largest megafauna still around,these herbivores weigh at least one tonne as adults. Today,there are 5 species found: White, Black,Sumatran, Indian and Javan. Rhinos are today under threat due to poaching for their horns,which are used in traditional medicine,and due to habitat destruction leading to declining availability of vegetation.