The pans failed for the third year running, and by the eighth week of filming the last standing water in the Mopane basin was a strip of mud perhaps forty metres across. Everything in the valley came to it, and everything in the valley waited its turn.
The herd at the centre of this episode is nineteen animals led by a cow we estimate to be fifty-eight years old. When the water finally went, she walked them two hundred and ten kilometres to a spring she last drank from as a calf. None of the younger cows had ever made that journey. She never stopped to search.
We followed at four hundred metres for thirty-four days, filming on long lenses from a moving vehicle. The sequence that closes the episode — the youngest calf at the front of the line, on a road she has now learned — was shot on the last morning before the rains broke.
