They say the grass is always greener on the other side, and no one takes that more literally than the wildebeests of the Serengeti in Tanzania. Every July, roughly 2 million of these determined grazers, along with zebras and other herbivores, set off on a journey north to the Masai Mara in Kenya in search of lush pastures and fresh water. The great migration, considered one of the seven wonders of the natural world, is a safari spectacle where survival is the prize.