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

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 rdce 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

Reproductive non-seasonality in rhinoceroses: A review of the in-situ literature and birth records of ex-situ institutions

Mammals whose breeding activity is triggered by seasonal photoperiodic cues typically maintain seasonal reproduction in zoos, with births accumulating to various degrees in spring. For zoo-kept rhinoceroses, accumulation of births in autumn has been suggested, which would make this group unusual. We compare birthing (and hence conception) patterns of free-ranging rhinoceros populations from the scientific literature with those of the global zoo populations based on birth data available from Species360, to facilitate deductions on the cues that trigger rhinoceros reproduction. The patterns do not indicate a photoperiodic element in rhinoceros reproduction but suggest suppression of conception in free-ranging populations at times of resource scarcity. This is not evident in zoos. However, a slight accumulation of autumn births, due to a slight reduction in births in spring, is visible in the zoo populations. Given rhinoceros gestation periods, this is linked to reduced conceptions in November–December. The most parsimonious interpretation is management-related, as has been suggested (Roth 2006, Int. Zoo Yb. 40(1): 130–143): not all facilities are prepared to allow mating at times when outdoor husbandry is reduced due to weather restrictions. Given the long interbirth intervals of rhinoceroses, missed conception opportunities of 1–2 months are unlikely to affect population demographics. Nevertheless, detailed recording of approaches to facilitate mating during winter months by those zoos that achieve this may increase the general skill of rhinoceros management