Abstract
Female wild black rhinoceroses in Zimbabwe were monitored non-invasively using faecal progesterone metabolite analysis and observation of reproductive behaviour. A postpartum period of reproductive inactivity of at least 4 months, followed by a period of 4-7 months of oestrous cyclicity, was detected in six multiparous females. Three-quarters of the oestrous cycles (n = 21) had a total duration (mean +/- SEM) of 26.8 +/- 1 days. Other types of cycle were characterized either by an extended luteal phase, lasting on average twice as long as the normal cycle, or by an extended follicular phase. These extended cycles may have resulted from early embryo loss and heat stress. Female rhinoceroses did not conceive before 8 months after giving birth and some females (n = 2) most likely aborted after 3.0-3.5 months of gestation. The detected period of cyclic oestrus occurred between May and March in females (n = 9), and there was a 3 month extended interoestrous interval in nulliparous females during the period of decreasing daylengths that can be presumed to be the period of poorest fertility for the black rhinoceros under tropical latitudes. In contrast, the period of optimum fertility in the Southern hemisphere coincided with the late spring and early summer, and corresponded to the early rainy season. As a result, a higher incidence of births was detected in the late rainy season, providing the lactating female with the most suitable environment in terms of nutritional requirements.
Highlights
The Rhinocerotidae appeared during the early Eocene, some 50 million years ago, and represent one of the most ecologically diverse and widespread families of megaherbivores (Owen-Smith, 1988)
The individual monitoring of six wild females in Zimbabwe showed that they did not conceive before 8 months after parturition when their calves survived and that they had very limited or no contact with males for 4–7 months after parturition. This is the first report of a postpartum period of reproductive inactivity in black rhinoceroses, postpartum anoestrus has been reported in captive white and Indian rhinoceroses
The hormone profiles obtained in females that could be monitored frequently during this period of reproductive inactivity showed fluctuating faecal progesterone metabolite concentrations and a high background concentration
Summary
The Rhinocerotidae appeared during the early Eocene, some 50 million years ago, and represent one of the most ecologically diverse and widespread families of megaherbivores (Owen-Smith, 1988). Five rhinoceros species survive today, all of which are endangered, and comprise a total of < 15 000 animals (Foose and Van Strien, 1997; Emslie and Brooks, 1999). The population of black rhinoceroses was estimated to be only 2600 in 1997 (Emslie and Brooks, 1999). As a result of the demand for rhinoceros horn, the remaining rhinoceros populations are exposed to a permanent threat of poaching. These populations are small and isolated, making them vulnerable to stochastic environmental, demographic or genetic factors (Bride et al, 1996). Remaining populations must present optimum breeding output, both in the wild and in captivity, which is far from being achieved (Lindemann, 1982; Kock and Garnier, 1993; Brett, 1998; Göltenboth, 1999; Garnier, 2001)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
