Seasonal feeding selectivity and browse use by black rhinoceroses (Diceros bicornis bicornis) in a semi-arid Namibian reserve

Abstract

Black rhinoceroses (Diceros bicornis, hereafter rhinos) are critically endangered, selective browsers whose foraging behaviour can shape ecosystems and affect population sustainability. Despite Namibia holding over 90% of the D. b. bicornis subspecies, local feeding behaviour data remain scarce. We studied the diet composition and browse selection along black rhino feeding paths in a game reserve located in a semi-arid savanna. We identified principal dietary species per season, evaluated browse selectivity and recorded browsing heights and bite diameters. Despite a diverse availability of browse species, only a few species made up the bulk of the diet, with Dichrostachys cinerea, Grewia bicolor, Catophractes alexandri and Colophospermum mopane (only in the dry season) being most important. Seasonal variation in species preferences and bite diameters was evident, whereas feeding height remained consistent across seasons, with rhinos foraging close to the ground. Our findings confirm black rhinos’ selective foraging and their potential role in limiting bush encroachment. However, the supplementation of polyethylene glycol to reduce tannin effects may have influenced the foraging patterns we observed, warranting further investigation. These findings are important for guiding ecological management, habitat suitability assessments, and sustainable rhino conservation, particularly in dryland ecosystems and fenced reserves where movement and diet choice are restricted.