Seasonal migration by white-eared kob in relation to resources.
In studies on a migrating population of >800 000 white-eared kob (Kobus kob leucotis) in Boma National Park, SE Sudan, movements into the dry season range in the N. part of the ecosystem were correlated with seasonally scarce supplies of food and water. In the dry season range, kob concentrated at densities of >1000 animals/km2 in low-lying meadows adjacent to permanent water supplies and consisting of Echinochloa pyramidalis and E. stagnina interspersed with Hyparrhenia rufa, which produced grass regrowth throughout the dry season due to the residual soil moisture. Movements into the wet season range were unrelated to food or water availability. The low rainfall grasslands on sandier soils in the south of the park, dominated by Heteropogon contortus, Setaria incrassata, Sporobolus ioclados and Panicum coloratum, were probably preferred during the wet season because they were less prone to surface flooding than other areas or because the species present were more nutritious than the tall H. rufa which was dominant elsewhere. Data on standing crop of grasses, and chemical composition of E. pyramidalis and H. rufa during the dry season, in habitats used by kob are given.