African elephants influence browse availability for black rhinoceroses in Gonarezhou National Park, Zimbabwe

Translocations are essential for the establishment of new populations of the critically endangered black rhinoceros (Diceros bicornis), but success will largely depend on forage availability. We investigated the degree of competition for woody browse between African savanna elephants (Loxodonta africana) and a recently reintroduced population of rhinoceroses in Gonarezhou National Park in Zimbabwe in the dry season of 2022. We examined overlap in space use and selection for plant species, stem diameters, and feeding height by measuring use of shrubs by both species at 75 sites across a range of topo-edaphic conditions. Areas heavily used by rhinoceroses had high shrub densities, were close to water, and were on alkaline soils with elevated conductivity. Sites with medium to high levels of rhinoceros use were nested within areas of high elephant use. We also observed high elephant use in areas not favored by rhinoceroses, occurring farther from water and having lower shrub densities. Both species avoided thickets on acidic soils. There was substantial overlap in feeding areas, the plant species selected, and foraging height, although elephants used stems with larger diameters than rhinoceroses. Feeding by elephants on woody plants often resulted in a proliferation of small-diameter coppice stems, which rhinoceroses used more than non-coppice growth. Elephants did not appear to favor small coppice stems, indicating a degree of elephant-induced facilitation of browse for rhinoceroses. Evidence for competition with elephants indicates black rhinoceroses may be best introduced into areas with a low elephant density.