Rhinoceros populations in Africa are under severe threat as a result of surging poaching rates and risk-mitigation strategies are continuously adapted in an attempt to ensure the survival of the species. This study compares faecal glucocorticoid metabolite (fGCM) levels of two age classes of limited free-ranging female white rhinos with fGCM levels of adult free-ranging female white rhinos. Subsequently, fGCM alterations in the limited free-ranging animals were monitored following routine dehorning as a measure of the animals' short-term physiological stress response.Baseline fGCM levels differed significantly between tested groups, with both freeranging and limited free-ranging adult animals showing significantly higher fGCM levels compared to limited-free ranging juvenile females. In contrast, baseline fGCM levels did not differ significantly between limited free-ranging and free-ranging adult individuals. Routine dehorning procedures resulted in a short-term stress response expressed by a significant increase in fGCM levels 48 h post-dehorning, with stress steroid levels returning to pre-dehorning concentrations 72 h after the procedure.
Unlike their wild counterparts, many white rhinoceros females in captivity fail to reproduce successfully such that current captive populations are not self-sustaining. The causes of the problem are poorly understood. Variation in cycle length and long periods of acyclicity are characteristics of the majority of these non-reproducing females in captivity but it is unknown whether these characteristics are a feature of reproductively successful free-ranging females. This study therefore aimed to monitor cyclic activity in a wild population of southern white rhinoceros at Lapalala Wilderness, South Africa, by measuring the concentrations of immunoreactive fecal progestagen metabolites (fPM).Five adult females were tracked twice per week for 20 months and if located a fresh fecal sample was collected. Reproductive events and group structural dynamics were also recorded and subsequently correlated with the fPM data. The baseline concentration of fPM was 0.69 ± 0.20 µg/g DW while concentrations during pregnancy were 30-to 400-fold higher. The females exhibited estrous cycle lengths of 30.6 ± 7.7 days and, based on fPM data, gestation length in one female was 502 ± 3 days. Year-round monitoring showed no clear evidence of seasonality in ovarian activity. During cyclic luteal activity females were often seen in the presence of a dominant bull. One female stopped cycling after removal of the local dominant bull and luteal activity only returned after a new bull was introduced. This suggests that white rhinoceros females in the wild might need external stimuli from a male to ovulate. These findings indicate that the irregular cyclicity reported for white rhinoceros housed in zoos and animal parks may result from conditions in captivity and account for reduced fertility.
Knowledge of the reproductive biology of wild animals can provide valuable information for the development of appropriate in situ and ex situ management plans. The present study aimed to establish a non-invasive protocol for monitoring faecal progestagen metabolite (FPM) patterns in wild female southern white rhinoceroses (Ceratotherium simum simum). Six adult females at Lapalala Wilderness, South Africa, were tracked and accurately identified at least once every week. Three animals gave birth during the study period. Fresh faecal samples were collected for 12 months and stored frozen at -20°C until analysis with an enzyme immunoassay utilizing an antiserum raised against 5a-pregnan-3b-ol-20-one which cross-reacts with a number of progestagens. Mean FPM concentrations were 35 to 64-fold higher during pregnancy (55-145 days before parturition) compared to postpartum (120-140 days after parturition) (P < 0.001). Also, the non-pregnant animals had mean FPM concentrations significantly higher than postpartum values (P = 0.006). Our results show that non-invasive FPM measurements provide information on the pregnancy status of wild female white rhinoceroses, and may be used for the detection of pregnancy in free-living individuals, without the necessity of immobilization and/or relocation of the animal. This information has potential value for optimizing breeding management of wild and captive populations.
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