How the work of Dian Fossey and David Attenborough helped protect the mountain gorilla. Watch video.

The natural world has lost one of its most preeminent figures this week as Titus, known as the Gorilla King, succumbed to old age and died on September 14, 2009.

Among the mountain gorillas of Rwanda, Titus reigns as king. Watch the full episode online.

NATURE retraces the life of Titus, silverback leader, from birth to present reign, spanning a tumultuous period in the history of a species and a nation in "The Gorilla King."

It was from a small hut in Rwanda that researcher and conservationist Dian Fossey observed that while gorillas may sometimes act tough, they are really gentle giants.