The Masai Mara National Reserve in southwestern Kenya is the stage for one of nature's greatest dramas: the Great Wildebeest Migration. Every year from July to October, over 1.5 million wildebeest, 200,000 zebra, and 500,000 gazelle cross the crocodile-infested Mara River from Tanzania's Serengeti in search of fresh pasture. The Mara is also home to the highest density of lion in Africa, the Big Five, and the Maasai people — seminomadic herders who have coexisted with wildlife for centuries.