The herds arrive from July
Around 1.3 million wildebeest, 200,000 zebras and 500,000 Thomson's gazelles circle the Serengeti-Mara ecosystem every year, following the rain and the fresh grass. In late June or early July the first herds reach the Kenyan side over the Sand River and through the Mara Triangle. Until September the animals then stand on the plains of the Masai Mara, the only part of the ecosystem where grass still grows in the dry season. The exact timing depends on the rain and shifts by 2 to 4 weeks from year to year.