Retrospective pathology review of captive black rhinoceros Diceros bicornis in the EAZA Ex-situ Programme (1995-2022)

Abstract

The husbandry of black rhinoceros Diceros bicornis is challenging due to a number of peculiar diseases affecting this species. Causes of mortality and morbidity were evaluated from 67 necropsy reports of black rhinos deceased in the EAZA Ex-situ Programme (EEP) in 1995–2022, and the prevalence of specific diseases were compared with previous surveys in the literature. Whereas some problems described as typical, such as haemolytic anaemia, aspergillosis or specific skin diseases presented at low prevalence, signs of iron overload disorder (IOD) were close to ubiquitous across animals, and skin disease, excessive tooth wear (often linked to impaction) and gastric ulceration were particularly prevalent. While this evaluation cannot add to understanding of the aetiology of these conditions, it emphasises the need to further investigate IOD and other diseases (which will require access to routine blood samples of both healthy and diseased animals facilitated by medical training). The findings also recommend further investigation of measures to reduce stress, possibly including that triggered by conspecifics as well as humans. Species-adequate nutrition still requires proactive approaches in providing dicot-based forages without resorting to monocot (grass) products.