Straw-coloured bats flock together during migration in Kasanka national park, Zambia. About 8 million bats make it one of Africa’s largest and most spectacular mammal migrations. The six-foot-wingspan bats live on just one-acre of forest on this huge continent. When they come home to roost after their daily hunt for fruit, each tree holds up to 10 tonnes of bats, making this the highest density mass of warm-blooded mammals on the planet | image by Will Burrard-Lucas