Each year around the same time, the circular great wildebeest migration begins in the Ngorongoro Conservation Area of the southern Serengeti in Tanzania and loops in a clockwise direction through the Serengeti National Park and north towards the Masai Mara reserve in Kenya.This migration is a natural phenomenon determined by the availability of grazing. The initial phase lasts from approximately January to March, when the calving season begins – a time when there is plenty of rain-ripened grass available for the 260,000 zebra that precede 1.7 million wildebeest and the following hundreds of thousands of other plains game, including around 470,000 gazelles