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

The effect of a warmed enema during ovum pick-up on subsequent in vitro oocyte maturation in Southern white rhinoceros (Ceratotherium simum simum)

BACKGROUND

Rhinoceros are currently one of the most threatened mammal species globally. Slow population growth, increased poaching and habitat destruction have led to increased conservation efforts for each species. Assisted reproductive technologies (ART) have been implemented in an attempt to aid reproductive outputs for the conservation of these endangered species. Developing species-specific ART programmes for wildlife have been challenging. Temperature control during oocyte recovery is essential for ensuring in vitro success.

OBJECTIVE

This study is the first to investigate the effect of enema warming prior to trans-rectal ovum pick-up (OPU) on in vitro oocyte maturation in Southern white rhinoceros (Ceratotherium simum simum).

METHODS

OPUs were performed on 20 rhinoceros cows from three different game farms in South Africa; oocytes were transported to one of two in vitro fertilisation laboratories for culture. The enema fluid was either warmed to 32 °C or not warmed prior to the OPU. Location of the farm, the different laboratories, ambient temperature, season, aspiration probe temperature, media type and enema temperature were investigated as predictor variables for oocyte maturation success.

RESULTS

After considering all other potential covariates, warming of the enema fluid was the only independent predictor of in vitro oocyte maturation success during this study.

CONCLUSION

Oocytes retrieved from rhinoceros cows that received an enema warmed to 32 °C were 2.3 times more likely to mature in vitro compared to oocytes from cows that received an unwarmed enema; the findings can be implemented in other rhinoceros ART programmes and in conservation efforts of other endangered mammalian species.

Comparative analysis of gestation in three rhinoceros species (Diceros bicornis; Ceratotherium simum; Rhinoceros unicornis)

This comparative analysis evaluated endocrine profiles and gestation length data of captive pregnant black rhinoceros (Diceros bicornis), white rhinoceros (Ceratotherium simum), and greater one-horned (GOH) rhinoceros (Rhinoceros unicornis). Hormone profiles were collected over three decades as part of pregnancy diagnoses. After the third month of gestation, the luteo-placental shift in progesterone production in pregnant rhinoceroses causes a significant increase in the concentration of faecal progesterone metabolites. We defined a laboratory-specific value of 1000 ng/g faeces as a threshold for incipient feto-placental progesterone production. Using this value allowed a comparison between species and revealed significant individual differences within a species. The mean ± SEM gestation days for reaching the 1000 ng/g faeces threshold were 89.5 ± 2.9 (range 56-138 days; n = 39) in black, 96.0 ± 2.6 (58-138; n = 39) in white, and 117.8 ± 5.3 (74-173; n = 19) in GOH rhinoceroses. For the calculations of gestation length, we complemented our results from three decades of reproductive monitoring with data from the literature, resulting in about 70 values for each species. Gestation length in the black, the white and the GOH rhinoceros was 460.6 ± 1.5 (range: 436 - 486), 503.8 ± 1.3 (range: 480 - 525) and 480.5 ± 1.1 (range: 453 - 505) days, respectively. Daylight length significantly affected gestation length, while the sex of offspring had no effect. On average, pregnancies with parturitions in spring and summer were one week shorter than those in autumn and winter. Although rhinoceroses are non-seasonal breeders, most parturitions in captivity occur in autumn and winter. We also analysed preconception endocrine profiles in the white rhinoceros. Conceptions in this species occurred after oestrous cycles of approximately 35 days (n = 18), 70 days (n = 3), 15 days (n = 1), after periods of ovarian inactivity (n = 5), and during a foal heat within one month after stillbirth parturition (n = 1). In conclusion, this study provides a comprehensive overview of gestational parameters in three rhinoceros species.

Medical grade honey: Hope for wounded white rhinos

South Africa is home to some of the world's most endangered wildlife, with the White rhinoceros (Cerathotherium simum) among its most threatened species due to its highly sought-after horn. Since the reproduction number is below the mortality rate, there is a decrease in rhinos year over year, urgently requiring changes and saving the survivors. In this study, the efficacy of medical grade honey (MGH) for wound care in rhinos was investigated. We presented a case series of seven rhinos with wounds of different etiologies, including gunshots and poaching. Four wounds were around the horns and three on the limbs. It was a challenge to take care and follow-up the wounds of these wild animals in their natural habitat. A well-balanced decision between the need of treatment and risk of immobilization is constantly evaluated. In the presented cases, MGH proved a novel tool with minimal intervention and maximal effectiveness. With the severity of the wounds taken into consideration, there was a rapid healing in all cases, while infection resolved when present. MGH creates a moist and anti-inflammatory wound environment, while promoting almost all aspects in the wound healing processes, such as autolytic debridement, angiogenesis and re-epithelialization. The efficacy of MGH has constantly been confirmed in other cases and literature as well. MGH forms a potent therapy for treating wounded rhinos, independent of the severity of the wound. The strong antimicrobial and healing properties make it an easy and versatile product that can be used in all kinds of wounds.

The female effect-how female receptivity influences faecal testosterone metabolite levels, socio-positive behaviour and vocalization in male Southern white rhinoceroses

Testosterone is known to be essential for sexual maturation as well as for the display of behavioural traits linked to reproduction. At the same time, external factors such as the presence of receptive females may affect testosterone levels, stressing the hormone's substantial role in reproductive success. It is therefore of major interest to investigate the links between androgens, behaviour and the social environment especially in species that rely on a resilient reproduction rate, such as the white rhinoceros (WR). We collected faecal samples of 16 male Southern WR (Ceratotherium simum simum) aged between 1 and 44 years from 11 European zoos. Audio and video recordings were simultaneously taken from five of the study males that were sexually mature and had direct contact with receptive females. Our results showed a positive correlation of faecal testosterone metabolite (fTM) concentrations and progressing age up until adulthood followed by a decline in older males. While previous reproductive success did not show any effect, the access to receptive females resulted in higher fTM levels. Thereby, fTM concentrations remained at the same level regardless of the receptivity phase, while social cohesion with respective females, affiliative behaviour as well as call rates of Pant and Hiss distinctly peaked during the receptive compared to the non-receptive periods. Conclusively, the immediate presence of receptive females poses a female effect that enhances the overall androgen levels in males and, thus, might facilitate their reproductive success. However, androgens do not seem to be the main driver of behavioural changes during courtship or mating. By linking endocrinological and socio-behavioural factors, we were able to provide an applicable basis for non-invasive monitoring of reproductive behaviour in male WR in captivity, thereby contributing to deeper understanding of potential reproduction impairments in a species whose population in captivity remains not fully self-sustaining.

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

Understanding the reproductive biology of the roan antelope (Hippotragus equinus) (É. Geoffroy Saint-Hilaire, 1803) is crucial to optimise breeding success in captive breeding programmes of this threatened species. In this study, the pattern of faecal androgen metabolite (fAM) production related to reproductive events (calving or birthing, mating, gestation, and lactation), sexual behaviours as well as environmental cues were studied in captive adult male roan antelope. Faecal sample collection and behavioural observations were carried out from August 2017 to July 2018 for three reproductive males participating in a conservation breeding programme at the Lapalala Wilderness Nature Reserve in South Africa. As a prerequisite, the enzyme immunoassay used in this study was biologically validated for the species by demonstrating a significant difference between fAM concentrations in non-breeding adults, breeding adults and juvenile males. Results revealed that in adults males, the overall mean fAM levels were 73% higher during the breeding period compared to the non-breeding periods, and 85% higher when exclusively compared to the lactation/gestation periods, but only 5.3% higher when compared to the birthing period. Simultaneously, fAM concentrations were lower during the wet season compared to the dry season, increasing with a reduction in photoperiod. With the exception of courtship, frequencies of sexual behaviours monitored changed in accordance with individual mean fAM concentrations in male roan antelope, the findings suggest that androgen production varies with the occurrence of mating activity and may be influenced by photoperiod but not with rainfall.

Managed wildlife breeding-an undervalued conservation tool?

Knowledge of and the technologies and resources applied to the ex situ care for wildlife have improved greatly in recent years. This has resulted in numerous successes bringing back populations from the brink of extinction by the reintroduction or restoration of animals from conservation breeding programmes. Controlled breeding of wildlife by humans is discussed controversially in society and in scientific circles and it faces a number of significant challenges. When natural breeding fails, Assisted Reproduction Technologies (ART) have been postulated to increase reproductive output and maintain genetic diversity. Furthermore, technical advances have improved the potential for successful collection and cryopreservation of gametes and embryos in many wildlife species. With the aim of creating a better understanding of why ex situ and in situ conservation of threatened species must complement each other, and under which circumstances ART provide additional tools in the rescue of a threatened population, we elucidate the current situation here by using as examples three different megavertebrate families: elephantidae, rhinoceridae and giraffidae. These mammal families consist of charismatic species, and most of their members are currently facing dramatic declines in population numbers. On the basis of these and other examples, we highlight the importance of captive zoo and other managed wildlife populations for species survival in a human dominated world. Without the possibility to study reproductive physiology in trained or habituated captive individuals, major advances made in wildlife ART during the past 20 years would not have been possible. This paper reviews the benefits and future challenges of large mammal conservation breeding and examines the role of assisted reproduction in such efforts.

The future of private rhino ownership in South Africa

Sustained poaching over the past decade has led to significant loss of black (Diceros bicornis) and southern white (Ceratotherium simum simum) rhinoceroses across South Africa. Whereas much research has focussed on the heavily targeted state-owned populations, there is little understanding of the trends and challenges faced by rhino populations held in the private sector. Private rhino ownership has increased substantially across South Africa over the past three decades, with over 42% of the entire rhino population now in private ownership. Although total rhino numbers on private properties are still increasing, the number of properties owning rhinos is declining. This suggests a move away from traditional extensive properties to large, single-species breeding facilities, which are less valuable from a conservation perspective. The economic impact associated with increased poaching of rhinos over the past decade is the major challenge to private rhino ownership and may encourage disinvestment in rhinos. Some private rhino owners advocate for trade in rhino horn to generate the funds necessary for continued protection of their animals. However, other options to reduce disinvestment, such as local community-engagement projects, are likely to be more favourably received by the wider conservation industry.