World Rhino Day was created to celebrate the world's five species of rhinoceros - The Black Rhino, Greater one-horned rhino, the Javan rhino, Sumatran rhino and White rhino. At 600kg, Sumatran rhinos are the smallest species, with White rhinos being the largest at over 3,500kg. Rhinos face multiple threats, including poaching for their horns. Human encroachment, loss of habitat and demand for rhino horn threatens all species with extinction.