At the heart of the Serengeti ecosystem lies an ancient phenomenon that is the largest movement of wildlife on earth. In pursuit of food and water, over a million wildebeest and half a million zebra and antelope migrate north from the Serengeti to the adjoining Masai Mara reserve in Kenya every year. Plains zebra and wildebeest often intermingle. They are complementary grazers, preferring different parts of the same grass. Zebra, with their superior vision and hearing, serve as an early warning system for the wildebeest. Given the choice, predators prefer wildebeest meat to zebra. So zebra are happy to offer the carnivores that choice.