James Bradley pirouettes slowly on the roof of his Land Rover. A 13-foot-long aluminum pole with an antenna on top is sticking out of a front pocket of his shorts. The radio in his hand crackles with static. Bradley makes three tight circles, sweeping the air with the antenna, until the radio finally beeps. “I’ve got her,” he says. “It’s Rainbow.”
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Rainbow is one of an estimated 20,000 plains zebras that wander across Botswana’s Makgadikgadi Pans, a bleached expanse of grasslands and blinding white salt flats in the Kalahari Desert. She is also one of ten mares outfitted with a radio collar, providing Bradley with valuable insights into southern Africa’s last great migration.
Bradley, 28, a tall, lean biologist from England’s University of Bristol, runs the Makgadikgadi Zebra Migration Research project, which was begun a decade ago to answer a critical question: Would an eight-foot-high electrified fence stretching 150 miles across the zebras’ territory disrupt their migration? The annual exodus, triggered by rains, is second only to the Serengeti’s in number of zebras. The project aims to understand the impact of fencing policies on wildlife not just here but, potentially, across Africa.
Much of wild Africa, contrary to its popular image, is in fact interrupted by fences and roads and enclosed within parks and preserves. But one of the continent’s largest intact ecosystems remains in northern Botswana, where poor soil and limited water have restricted human development. Formed by a string of national parks and protected areas, the wilderness zone covers some 33,000 square miles, an area larger than South Carolina.
The fence, which the Botswana government installed on the western edge of the Makgadikgadi Pans National Park in 2004, was primarily intended to protect cattle on neighboring rangelands from lions that live in the park. But wildlife experts became concerned about the barrier’s impact on zebras. They had reason to worry, given Botswana’s disastrous history with fences. In 1983, during a devastating drought, at least 50,000 wildebeest died in the central Kalahari because a fence blocked their route to water. It had been erected to prevent the spread of disease from wildlife to cattle.
But trying to predict how the new fence would affect the vast zebra herds that rely on that expanse of parkland was no easy task. Bradley’s predecessor, Christopher Brooks, who started the zebra research project and now works on a conservation project in Angola, Namibia and Botswana, was “concerned that a fence could have serious negative consequences,” he says, “but there was no solid ecological data” about the zebras and their migration.
Despite being among the most recognizable of large African animals, as well as a cousin of the domestic horse, zebras and their extraordinary movements turn out to be rather mysterious.
Zebras come in three distinct species: plains, mountain and Grévy’s; plains zebras are the most widespread, occurring throughout much of southern and eastern Africa. As members of the Equus genus, they are closely related to horses and wild asses. (Zebras aren’t well suited to domestication, however; they are unpredictable and have been known to attack people trying to handle them.)
During the dry season, zebras live along the Boteti River, the only regular source of water. When the rains come, in early summer, the herds move east to open grassland, where temporary pools fill with water, and then on to the rain-filled salt pans, where nutritious grasses grow on the periphery.
Bradley and I are driving some 25 miles east of the Boteti when we catch up with Rainbow. The first summer showers fell a week before, prompting 20,000 zebras to leave the river and file into these verdant pastures, trusting in puddles to sustain them on their journey to their wet season range alongside the salt pans. Rainbow is grazing with a few dozen others. Despite her name, she is as black and white as the next zebra. “She was named by a donor’s 6-year-old daughter,” Bradley says with a smile.