Born to Move: Astonishing Photos of Great Migrations

Researchers spent two and a half years studying where and why animals move. Every year, zebras leave the flooded Botswana fields and embark on a fascinating, but deadly, 150 mile journey through the desert inferno of the African plains to satisfy their instinctual need for salt. "That's a ridiculous migration," said Rory Wilson, the lead scientist on the project. "They have to capitalize on the time that it rains when they can get to the salts." (Courtesy National Geographic)