The Bats of Kasanka

Each year in October, up to 8 million straw-coloured fruit bats arrive overnight in Kasanka National Park to spend two months gorging themselves on the abundant fruit that grows in the reserve. The national park covers a mere 390 square kilometres of land in northeastern Zambia, but it has perhaps the greatest concentration of mammal biomass on Earth.

The synchronous fruiting of wild loquat, red milkwood and water berry enables the millions of bats to feed, and they consume up to twice their own body weight every night. Their intense activity takes its toll on the forest, stripping the trees bare and, over time, killing them.

Straw-coloured fruit bats are a migratory species living in large, conspicuous colonies on the edge of forests, towns and cities with a range covering the tropical belt of Africa. Bats are now being seen as the primary dispersers of seeds in the tropics and essential for the regeneration of Africa’s tropical forests.

The Kasanka colony is unique for its vast size and the mystery that surrounds the bats’ movements. Every night the bats pour out across the sky, shading it in every direction for a radius of 40 miles or more. By the end of December they have moved on. Until now, no-one knew exactly where they went, but new satellite tracking research is shedding some light on their migration.

Bat biologist Heidi Richter, from the University of Florida, has been fitting bats with collars powered by a solar panel to trace the migration. After six months, she lost touch with them at a point 1,200 miles distant.

‘The four we tracked disappeared somewhere over the Democratic Republic of Congo: either there was not enough sun for the charge, or they chewed the collar off – or they were chewed themselves. I like the mystery – there is still so much to be discovered.’