In mammalian predators, prey size typically increases with body size, such that most carnivores weighing >21.5 kg specialize on prey weighing ≥45% of their own mass. By hunting in packs, endangered African wild dogs (Lycaon pictus) are able to feed primarily on ungulates weighing >100% of their own individual mass and, in most populations, wild dogs specialize on such large prey. However, we show that wild dogs living outside protected areas in northern Kenya fed primarily on Kirk's dikdiks (Madoqua kirkii), small antelope weighing just 15% of wild dog body mass. We estimated that dikdiks constituted 70% of the prey biomass consumed by wild dogs. Despite feeding on small prey, pack size, home-range size, and vital rates in this population were similar to those recorded in protected areas where wild dogs specialize on much larger ungulates. The energy content of a dikdik was about one-tenth that of the 2nd most important prey, impala (Aepyceros melampus). However, because dikdiks occurred at high population densities, the 2 prey species had apparently comparable hunting profitabilities. Wild dog packs ate more small (<10-kg) prey when confined to a breeding den. Also, packs living on commercial ranches consumed fewer small prey than did those living on community lands where larger prey were depleted. However, demographic parameters were similar in the 2 land uses. Although livestock occupy virtually the whole area, wild prey have persisted because local Masai and Samburu pastoralists do not traditionally hunt wild ungulates. This tradition has helped wild dogs to recolonize successfully and to reach densities comparable with those recorded in protected areas. The apparent ability of wild dogs to persist on small prey, in a livestock-dominated ecosystem, suggests that other important populations might occur, or be recoverable, in Africa's unprotected rangelands.