Today, the rhinoceros is one of the planet's rarest animals, with three of its species on the brink of extinction.

They are hulking beasts from prehistory, virtually unchanged over 25 million years. Once they roamed the Earth in millions, numbering hundreds of species of all shapes and sizes; today, the rhinoceros is one of the planet's rarest animals, with three of the remaining five species on the brink of extinction. NATURE trails rangers through the savannahs of South Africa, the grasslands of India and the jungles of Indonesia, and visits rhino fertility experts at an American zoo, detailing efforts to protect rhinos from poachers, relocate them to new habitats and breed them in captivity. Along the way, the program offers fascinating close-up scenes of the pachyderms in their natural habitats, from a pulse-quickening charge by a black rhino to an Indian one-horned rhino nursery full of mothers and calves, and much more.