Reproductive performance parameters in a large population of game-ranched white rhinoceroses (Ceratotherium simum simum)

Abstract

The population of free-roaming white rhinoceroses (Ceratotherium simum) is under serious threat. Captive breeding of this species is therefore becoming more important, but this is challenging and often not successful. Obtaining reproductive reference values is a crucial aspect of improving these breeding results. In this study performed between 2008 and 2016, reproductive performance was analysed in 1,354 animals kept in a 8000 hectares game-ranched environment. Descriptive statistics of this captive population showed an average annual herd growth (%) of 7 .0±0.1 (min -9 –max 15). Average calving rates were calculated as an annual calving rate of 20% and biennial calving rate of 37% adult females calving per year. 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. Furthermore, translocations of animals did not interfere with reproductive success in terms of inter-calving periods or age at first calving. 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. Our results did not show any significant skewed progeny sex ratios. Weather observations showed no significant influence of rain or season on sex ratios of the calves.

Combining molecular and incomplete observational data to inform management of southern white rhinoceros (Ceratotherium simum simum)

“…The average ACR and CI observed in this study were 18.6% and 3.7 years, respectively; which could be interpreted as a very poor fecundity population based on the guidelines provided by the Southern African Development Community Rhino Management Group (Du Toit 2006). The reproductive performance of the population in this study was less than that reported in other non-captive populations, for which ACR and CI ranged from 20 to 50% and 2.4 to 3.3 years, respectively (Rachlow and Berger 1998;Kretzschmar 2001;Ververs et al 2017). The ACR target is a value greater than 33%, which corresponds to a CI of 3 years (Du Toit 2006).…”

“…No evidence of natal sex-ratio skewness was found, which supports previous studies. Natal sex-ratio skewness toward males has been reported in captive SWRs (Zschokke et al 1998;Kretzschmar 2001;Linklater 2007), whereas non-captive populations kept at lower stocking densities have been reported to be in the expected 50:50 sex ratio (Ververs et al 2017). The average ACR and CI observed in this study were 18.6% and 3.7 years, respectively; which could be interpreted as a very poor fecundity population based on the guidelines provided by the Southern African Development Community Rhino Management Group (Du Toit 2006).…”

“…Pedigree D was subsequently used to estimate population demographic parameters, including: (1) annual calving rate (ACR ), defined as the annual percentage of dams that gave birth of the total number of reproductive age dams; (2) percentage of herd growth (HG-see Eq. 1, below), described as net increase in size of the herd as a result of newborn calves divided by the size of the herd at the beginning of the year (Ververs et al 2017); (3) mean age of first calving of dams born in the reserve; (4) mean total number of offspring produced per sire and dam over the period of observation; (5) natal sex ratio; (6) the effective population (N e ); and (7) calving interval (CI) for multiparous females. The estimation of percentage of HG shown in Eq.…”

“…The high variability of observed ACR in this study, which ranged from 0 to 50%, resulted from a small number of breeding dams and was the main reason for the low apparent fecundity of the population in this study. Aberrant ovarian cycles and pathological lesions of female reproductive tracts have been reported in SWRs kept in both captivity and non-captivity, and these defects are believed to cause low reproductive performance (Hermes et al 2006;Roth et al 2018;Ververs 2018). Studies conducted in captive populations led to the hypothesis that prolonged estrogenic exposure from phytoestrogens found in plants that the cows fed on may be responsible for the aberrant ovarian function (Tubbs et al 2017).…”

Reproductive events and respective faecal androgen metabolite concentrations in captive male roan antelope (Hippotragus equinus)

“…Thus, many breeding programmes have contributed to a better understanding of the extrinsic and intrinsic factors and requirements necessary for reproductive success, especially by documenting female reproductive physiology and performance [ 12 , 13 ]. However, for the context of captive breeding programmes, males play as equally an important role as females [ 14 , 15 ]. Thus, for species participating in conservation breeding programmes, a better understanding of the male reproductive behaviour and related physiology is crucial to optimise breeding efforts for threatened wildlife species.…”