The roar of hundreds of wildebeests anticipates the stampede. On the other side of the river, the herd leaders overcome fear inch by inch and bring their hooves closer to the edge of the cliff. Suddenly, they plunge into the void: dozens of individuals rush towards the water and frantically cross the Mara River through a cloud of dust. On the other side of the river, about thirty vehicles take positions, loaded with wide-eyed tourists with cameras at the ready. It’s no wonder. The Great Migration in Tanzania and Kenya, in which about two million wildebeests, zebras, and gazelles follow the rains across the Serengeti and Masai Mara plains, is one of nature’s greatest spectacles, especially when the crossing of crocodile-infested rivers occurs. But the purity of this treasure is in danger: a year ago, South African guide Nick Kleer published embarrassing images showing dozens of tourists outside their cars, something forbidden, in front of a barrier of 150 vehicles blocking the animals’ passage.