In the short-term, this may be off-set by an enhanced tolerance for low quality food and by seasonally mobilising fat reserves however, the long-term fitness consequences require further study. We speculate that the lack of specialised grazing adaptations may increase foraging costs in rhinoceros, through reduced harvest- and handling-efficiencies of grasses. Although black rhinoceros are generally considered strict browsers, the most significant shift in diet occurred as rhinoceros increased their preferences for grasses in the presence of elephant. Despite being unable to generalise beyond our study sites, our observations support the predictions of competition theory (as opposed to optimality theory) by showing (1) a clear seasonal separation in resource use between these megaherbivores that increased as resource availability declined, and (2) rhinoceros changed their selectivity in the absence of elephant (using an adjacent site) by expanding and shifting their diet along the grass-browse continuum, and in relation to availability. Using the histological analysis of faeces, we explore this phenomenon for African elephant Loxodonta africana and black rhinoceros Diceros bicornis in the Addo Elephant National Park, South Africa, where the accumulated impacts of elephant have reduced browse availability.

However, there exists little empirical evidence on how food resources are shared within this guild, and none for direct competition for food between megaherbivores. Consequently, they are considered a separate trophic guild that structures the food niches of coexisting large herbivores. In African large herbivore assemblages, megaherbivores dominate the biomass and utilise the greatest share of available resources.

West african black rhino number