The seasons bring life to the valleys forged by the African rivers, but they also play a part in nature's tragedies. For most of the year, the Mara River flows peacefully through the wide grassplains of Southern Kenya, but during the dry months it displays the ultimate life-and-death struggle: the crossing of hundreds and thousands of wildebeests.\nThe great herds migrate from the south to their winter grazing grounds on the western bank of the river. The zebras are the first to brave the crossing of the Mara, despite the danger from the crocodiles. After a meagre diet of barbel, the crocodiles feast.\nThen the huge wildebeest herds arrive at the Mara's banks. Driven by instinct, they too forge the crocodile-infested river. After a gruelling river crossing, the wildebeests finally reach their winter pastures. They remain here until the summer rains prompt them to return to the Serengeti, but this involves crossing the Mara once more.

The seasons bring life to the valleys forged by the African rivers, but they ...