Black wildebeest (Connochaetes gnou) and blesbok (Damaliscus pygargus) probably migrated seasonally between the western Free State plains and the Maluti mountains adjoining Lesotho. In Botswana’s central Kalahari, a wildebeest population of c. 200,000 animals collapsed when their movement was blocked by a veterinary cordon fence during extreme drought conditions ( Spinage, 1992 and Fynn and Bonyongo, 2011).