These graceful antelopes of central Africa’s well-watered savannas and floodplain grasslands are best known for their annual migration, which produces one of the natural world’s great spectacles.
The Sudd wetlands of southern Sudan, nourished by the White Nile, are home to an astounding number of white-eared kob—hundreds of thousands of animals. When joined by tiang antelopes and Mongalla gazelles they form enormous migrating herds of more than 1.2 million individuals. Thickly packed columns of these animals in motion can stretch a staggering 50 miles long and 30 miles across. Such herds rival the Serengeti’s teeming masses of wildebeests for the title of the world’s most massive—and awe-inspiring—mammal migration.
Dry season finds the Sudd’s white-eared kob in the northern part of their North Dakota-size range, which occupies a critical ecological niche between Africa’s lush tropical forests and its arid Sahara sands. There the animals gather in herds to graze low-lying meadows with access to permanent water.
But wet season means a move en masse to the south, as far as 930 miles, as the kob chase nutritious shortgrasses and seek lands less susceptible to flooding.
When not on the move, white-eared kob live in much smaller groups and visit the same feeding and breeding grounds again and again. Males gather in numbers of 15 to 20 at permanent breeding sites known as leks. There each male establishes his own, smaller territory and patrols its borders to hold his ground against competitors. Larger female herds visit the leks to choose mates from among the males. Those males able to hold prime positions in the center of the larger, circular group lek tend to have the most success.
When Sudan’s violent civil war wound down, the white-eared kob provided cheering news as a stunning wildlife success story. The animal's status in the region had been unknown during a quarter-century of violent conflict that halted conservation work. Many feared the worst.
But in 2007, National Geographic Explorer-in-Residence J. Michael Fay conducted an aerial survey and was shocked to discover that white-eared kob had not only survived but thrived in numbers that awed even the most experienced African naturalists.