Penile edema with prolapse, which prevents normal mating, has been described. Reproductive pathologies in male rhinoceros have rarely been noticed. Furthermore, pathologies of the female genital tract, such as endometrial and ovarian cysts, muco- and pyometra, and uterine leiomyoma, adenoma and adenocarcinoma have been documented to occur more in captive rhinoceros than in their free-ranging counterparts. Captive populations kept outside their natural habitat also show a high incidence of prolonged periods of anestrus, with more than half of these females remaining acyclic or without ovulation of preovulatory follicles. One of the reasons might be, that in captivity, females are frequently bred for the first time at an older age and that the social hierarchy in smaller groups is often compromised. However, for reasons that are currently not understood, the rate of reproduction is extremely low among captive-born Southern white females. Wild-caught southern white rhinoceroses will readily breed in captivity if given appropriate space and food, and if other female rhinos of breeding age are present. Most reports on reproductive performances in zoological institutions have been about individuals or small groups of rhinoceros. Endeavours to breed white rhinoceros in captivity have led to growth and expansion of population numbers in the past with improved genetic diversity and an increased economic return of investment.
If the current population numbers continue to diminish at the present rate, with over 1,200 Southern white rhinoceros being poached in South Africa alone in 2015 and over 1,000 in 2016, captive breeding programs may be crucial to prevent extinction. Dwindling population numbers in the wild are mainly due to the inherent value of horn. However, poaching has increased dramatically since 2008, due to a huge demand for rhino horn, and is causing a rapid decline in wild rhinoceros populations and more specifically, of Southern white rhinoceros (SWR) numbers in South Africa. South Africa represents the major habitat for the Southern white rhinoceros, conserving 16,255 individuals in the wild in 2007. With numbers as low as 50 in the wild in the early 1900s, this subspecies has recently increased to a population of almost 20,000 individuals. The Southern white rhinoceros was exemplary for a major conservation success story. The white rhinoceros ( Ceratotherium simum) is considered to exist of two subspecies: the Southern white rhinoceros ( Ceratotherium simum simum), and the much rarer Northern white rhinoceros ( Ceratotherium simum cottoni). Weather observations showed no significant influence of rain or season on sex ratios of the calves.
Our results did not show any significant skewed progeny sex ratios. Multivariate models showed a clear seasonal calving pattern with a significant increase of the number of calvings during December–April when compared to April–December. Furthermore, translocations of animals did not interfere with reproductive success in terms of inter-calving periods or age at first calving. Females had a median age of 83.2 months at first calving (IQR 72.9–110.7) and inter-calving intervals of 29.2 (IQR 24.6–34.8) months. Average calving rates were calculated as an annual calving rate of 20% and biennial calving rate of 37% adult females calving per year. Descriptive statistics of this captive population showed an average annual herd growth (%) of 7.
In this study performed between 20, reproductive performance was analysed in 1,354 animals kept in a 8000 hectares game-ranched environment. Obtaining reproductive reference values is a crucial aspect of improving these breeding results. Captive breeding of this species is therefore becoming more important, but this is challenging and often not successful. The population of free-roaming white rhinoceroses (Ceratotherium simum) is under serious threat.
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