Food preferences and feeding interactions among browsers and the effect of an exotic invasive weed Chromolaena odorata on the endangered black rhino (Diceros bicornis), in an African savanna.
Biodiversity changes, often resulting from climate change, land transformation, and the transportation of organisms across geographical barriers are among the most important human induced global changes. To optimize the spatial allocation of conservation efforts, and how to best protect indigenous species, requires an understanding of the principal determinants that structure ecological communities and ecosystems. We studied community-level interaction among a diverse assemblage of specialist and generalist browsers in an African savanna. Hluhluwe-iMfolozi Park (HiP), South Africa, hosts a complete assemblage of vertebrate species across all trophic levels and contains a diverse guild of large browsers. Using species abundance distributions (SADs) we graphically illustrate the diversity and abundance of woody species that comprise six structural habitat types within HiP. We calculated the Shannon-Wiener index and Pianka’s niche overlap to characterise the utilization of forage across habitat types among different browser groups. By using individual plant traits we investigated mechanisms of resource partitioning. We specifically investigated the effect of the temporal expansion of an exotic invasive plant (Chromolaena odorata) on the critically endangered black rhino using GIS and statistical analyses. We found that lower lying habitat types were important forage resources for browser species and individual plant traits that are highly correlated with digestibility strongly predicted browser preference. Black rhino used different strategic and metabolic mechanisms to successfully compete within the same forage height range of other, smaller, browsers. C. odorata has negatively impacted forage species utilization and has led to a spatial reorganization of the population of black rhino. This may partly explain the recent decline in the population. The principles within metapopulation management can be used to successfully conserve endangered species. High diversity of browse across three dimensions (diversity, abundance and maximum height) relative to area facilitates a high diversity and abundance of different browsing herbivores. Therefore the spatial configurations of resources ranging from topological attributes to the individual plant traits are essential to maintaining viable populations of many co-occurring species within conservation areas of limited extent.