Competition and coexistence among short-grass grazers in the Hluhluwe-iMfolozi Park, South Africa

Abstract

Coexistence among grazing ungulates has been related to differences in grass height and grassland types selected, underlain by morphological distinctions. Nevertheless, resource competition may arise when smaller species depress grass height below that suitable for larger species, whereas competition may be counteracted by facilitation when larger species increase the extent of high-quality grassland available. We investigated resource-use overlap between white rhinoceros ( Ceratotherium simum (Burchell, 1817)), blue wildebeest ( Connochaetes taurinus (Burchell, 1823)), and Burchell’s zebra (Equus burchelli (Gray, 1824)) in the Hluhluwe-iMfolozi Park in South Africa. We recorded the grassland type favoured, grass species utilized, grass height grazed, and greenness selected during the dry seasons of 2 years. Blue wildebeest shifted their grazing away from lawn grassland in the drier year, whereas Burchell’s zebra favoured lawn grassland only in the relatively wet year. White rhinoceros concentrated their feeding on lawn grassland throughout the dry seasons of both years, and favoured shorter grass than the other two grazers. Species characterizing grazing lawns contributed relatively more to the grass used by white rhinoceros in the drier year. Resource competition was potentially ameliorated by widened availability of lawn grassland promoted by white rhinoceros grazing. This counterbalancing of feeding competition and habitat facilitation enables the coexistence of these grazers despite similar food requirements.