The Serengeti exodus may be more famous, but Africa’s greatest annual mammal migration is the eight to ten million fruit bats that descend on Kasanka National Park in Zambia between October and December.
The specter of a bat-filled sky overwhelms the senses. “It’s absolutely one of the most mind-blowing and mesmerizing things I have ever witnessed,” says former park ecologist Frank Willems.
And then there are the sounds: millions of flapping wings and countless cries echoing across the secluded savanna of northern Zambia, one of Africa’s least visited but most rewarding wildlife regions.
The experience is especially potent at dawn, the primal scene set against a blood-red sky filled with the mulchy aroma of an early rain-season shower.
Kasanka’s bat migration is believed to be the world’s highest density of mammalian biomass—an estimated 5.5 million pounds of airborne animal. Or, as a safari guide put it: like 700 elephants flying overhead.
At dusk, some 7,500 bats per second lift from the forest, almost covering the entire sky overhead. The following morning, gaze skyward to witness massive dark whirlpools of bats, circling the forest in a spectacle worthy of Alfred Hitchcock. “It just goes on, and on, and on,” Willems says.
Kasanka isn’t the only natural lure in the region. It is but one of more than a dozen national parks and game reserves comprising a wildlife corridor that stretches across north-central Zambia and into parts of neighboring Malawi and the Congo.
The lush Luangwa River and Rift Valley boasts three of these preserves, including the world-renowned South Luangwa National Park with its large elephant herds and healthy populations of buffalo and hippos. The region’s Lake Bengwuela Swamps are one of Africa’s greatest wetlands, home to copious birdlife and antelope.
This article originally appeared in the National Geographic book Four Seasons of Travel.