The importance of large pans and surrounding bushveld for black rhino (Diceros bicornis ssp. bicornis) habitat use in the Kalahari: implications for reintroduction and range expansion

Abstract

In the Kalahari region of southern Africa, recurrent droughts can affect local livestock production and even lead to the loss of traditional farmland. As a result, the wildlife economy has grown in importance as a profitable approach to the sustainable use of native game species adapted to these challenging climatic conditions. This has led to restoration efforts in the region that have brought back wildlife including the critically endangered black rhino (Diceros bicornis). To understand the interrelationship between a reintroduced black rhino population and a rural Kalahari wildlife reserve, this research project aimed to decode the key drivers of black rhino habitat use based on a multiscalar approach of combined aerial and ground information on ecogeographical variables (vegetation and artificial habitat components) together with spatial rhino location and individual movement data. On average, black rhino home ranges were found to be 67 ± 20 km2, with core areas of 24 ± 11 km2. These are predominantly covered by the landscape types of bushveld and calcareous pans. Analysis of the different landscape factors present in the reserve showed that vegetation heterogeneity, vegetation density, vegetation damage, browse availability and waterhole density were significantly higher in the pooled core areas of the total population compared to less frequented areas. Furthermore, a binary logistic regression model predicted that browse availability and vegetation heterogeneity of medium to large woody species to be the most significant effect on black rhino habitat use. The model also showed a negative correlation with Acacia spp. saplings, which can be explained by the decline or absence of saplings in the core areas due to the continuous feeding pressure of black rhinos and other herbivores. Evaluation of black rhino habitat use and spatial distribution indicates a strong preference for the mosaic of microhabitats around calcareous pans and surrounding lunette dunes covered by bushveld. Together with the year-round availability of water (rain-fed lakes and artificial waterholes), these focal points are of high ecological importance and provide suitable habitat conditions that may highlight the potential for further black rhino reintroduction and range expansion, as well as general rewilding efforts in the region.