Effects of Artificial Water Provision on Migratory Blue Wildebeest and Zebra in the Makgadikgadi Pans Ecosystem, Botswana

In migratory tropical ecosystems governed by water availability, artificially altering water availability can affect herbivore distribution and movement. The Makgadikgadi Pans, Botswana, sustains approximately 10,000 blue wildebeest (Connochaetes taurinus) and 24,000 plains zebra (Equus quagga) migrating between a dry season range with permanent water and a rainy season range with productive grasses. Artificial water points (AWPs) have been created by pumping some natural waterholes in the rainy season range. We combined data from aerial surveys and from GPS collars on 20 and 12 zebra pre- and post-AWP installation, respectively, and on 17 wildebeest post-AWP, to test hypotheses relating to large- and small-scale movement patterns. Post-AWP, a higher proportion of wildebeest, but not zebra, were in the rainy season range during the dry season. Post-AWP zebra migration to their rainy season range occurred longer after rainfall cessation than pre-AWP, though this period was still shorter than that of wildebeest (one month compared to three). The effect of proximity to waterholes on probability of space use varied seasonally for both species and followed opposing trends, suggesting resource partitioning or competition effects. Both species visited AWPs more than natural waterholes, particularly wildebeest in the dry season. Wildebeest movement patterns were more likely to be disturbed by AWPs, which could cause the development of residency and reduce population resilience. Management interventions, such as AWPs, can affect species to different extents, so the responses of several species should be assessed to determine the level of disturbance to migratory ecosystem resilience and functioning.