• 98 Efficacy of commercial equine semen freezing extenders for cryopreservation of southern white rhinoceros (Ceratotherium simum simum) sperm

      Young, Carly; Ravida, Nicole; Pennington, Parker M.; Durrant, Barbara S. (2019)
      Once nearly extinct in the wild, the southern white rhinoceros is currently listed as near threatened by IUCN. This status is likely to change as poaching continues to escalate....
    • Advances in conservation endocrinology: The application of molecular approaches to the conservation of endangered species

      Tubbs, Christopher W.; McDonough, C. E.; Felton, Rachel G.; Milnes, Matthew R. (2014)
      …In this review we examine various in vitro approaches we have used to compare estrogen receptor binding and activation by endogenous hormones and phytoestrogens in two species of rhinoceros; southern white and greater one-horned. We have found many of these techniques valuable and practical in species where access to research subjects and/or tissues is limited due to their conservation status....
    • Contrasting evolutionary history, anthropogenic declines and genetic contact in the northern and southern white rhinoceros (Ceratotherium simum)

      Moodley, Yoshan; Russo, Isa-Rita M.; Robovský, Jan; Dalton, Desiré L.; Kotzé, Antoinette; Smith, Steve; Stejskal, Jan; Ryder, Oliver A.; Hermes, Robert; Walzer, Chris; et al. (2018)
      The white rhinoceros (Ceratotherium simum) has a discontinuous African distribution, which is limited by the extent of sub-Saharan grasslands. The southern population (SWR) declined to its lowest number around the turn of the nineteenth century, but recovered to become the world's most numerous rhinoceros....
    • Estrogenicity of captive southern white rhinoceros diets and their association with fertility

      Tubbs, Christopher W.; Moley, Laura A.; Ivy, Jamie A.; Metrione, Lara C.; LaClaire, Sydney; Felton, Rachel G.; Durrant, Barbara S.; Milnes, Matthew R. (2016)
      …In this study, we investigate the role of dietary phytoestrogens in this reproductive phenomenon by characterizing activation of southern white rhinoceros (SWR) estrogen receptors (ESRs) 1 and 2 by diet items from nine North American institutions and comparing female SWR fertility to total diet estrogenicity. Of the diet items tested, alfalfa hay and soy and alfalfa-based commercial pellets were found to be the most potent activators of SWR ESRs.…
    • Evaluating recovery potential of the northern white rhinoceros from cryopreserved somatic cells

      Tunstall, Tate S.; Kock, Richard; Vahala, Jiri; Diekhans, Mark; Fiddes, Ian; Armstrong, Joel; Paten, Benedikt; Ryder, Oliver A.; Steiner, Cynthia C. (2018)
      The critically endangered northern white rhinoceros is believed to be extinct in the wild, with the recent death of the last male leaving only two remaining individuals in captivity. Its extinction would appear inevitable, but the development of advanced cell and reproductive technologies such as cloning by nuclear transfer and the artificial production of gametes via stem cells differentiation offer a second chance for its survival. In this work, we analyzed genome-wide levels of genetic diversity, inbreeding, population history, and demography of the white rhinoceros sequenced from cryopreserved somatic cells, with the goal of informing how genetically valuable individuals could be used in future efforts toward the genetic rescue of the northern white rhinoceros. We present the first sequenced genomes of the northern white rhinoceros, which show relatively high levels of heterozygosity and an average genetic divergence of 0.1% compared with the southern subspecies. The two white rhinoceros subspecies appear to be closely related, with low genetic admixture and a divergent time <80,000 yr ago. Inbreeding, as measured by runs of homozygosity, appears slightly higher in the southern than the northern white rhinoceros. This work demonstrates the value of the northern white rhinoceros cryopreserved genetic material as a potential gene pool for saving this subspecies from extinction.
    • Exploring the limits of saving a subspecies: The ethics and social dynamics of restoring northern white rhinos (Ceratotherium simum cottoni)

      Ryder, Oliver A.; Friese, Carrie; Greely, Henry T.; Sandler, Ronald; Saragusty, Joseph; Durrant, Barbara S.; Redford, Kent H. (2020)
      The northern white rhino (Ceratotherium simum cottoni) is functionally extinct with only two females left alive. However, cryopreserved material from a number of individuals represents the potential to produce additional individuals using advanced reproductive and genetic rescue technologies and perhaps eventually a population to return to their native range. If this could and were done, how should it be done responsibly and thoughtfully. What issues and questions of a technical, bioethical, and societal nature will it raise that need to be anticipated and addressed? Such issues are explored in this article by an interdisciplinary team assembled to provide context to the northern white rhino project of the San Diego Zoo Global.
    • Ovulation induction in anovulatory southern white rhinoceros (Ceratotherium simum simum) without altrenogest

      Pennington, Parker M.; Marshall, Kira L.; Capiro, Jonnie M.; Felton, Rachel G.; Durrant, Barbara S. (2019)
      Lack of ovulation is common in captive southern white rhino females and contributes to poor reproductive success. We show that ovulation can be induced efficien
    • Reconsidering the use of soy and alfalfa in southern white rhinoceros diets

      Tubbs, Christopher W.; Durrant, Barbara S.; Milnes, Matthew R. (2017)
      The captive southern white rhinoceros (SWR) population is not currently self-sustaining due to the reproductive failure of captive-born females. Our research into this phenomenon points to chemicals produced by plants common to captive diets, such as soy and alfalfa, as possible causes...
    • Reproductive performance parameters in a large population of game-ranched white rhinoceroses (Ceratotherium simum simum)

      Ververs, Cyrillus; Langhout, Martine van Zijll; Hostens, Miel; Otto, Michelle; Govaere, Jan; Durrant, Barbara S.; Soom, Ann Van (2017)
      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.
    • Rewinding the process of mammalian extinction

      Saragusty, Joseph; Diecke, Sebastian; Drukker, Micha; Durrant, Barbara S.; Friedrich Ben-Nun, Inbar; Galli, Cesare; Göritz, Frank; Hayashi, Katsuhiko; Hermes, Robert; Holtze, Susanne; et al. (2016)
      With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name “Conservation by Cellular Technologies.” The outcome of this meeting and the proposed road map that, if successfully implemented, would ultimately lead to a self-sustaining population of an extremely endangered species are outlined here. The ideas discussed here, while centered on the northern white rhinoceros, are equally applicable, after proper adjustments, to other mammals on the brink of extinction. Through implementation of these ideas we hope to establish the foundation for reversal of some of the effects of what has been termed the sixth mass extinction event in the history of Earth, and the first anthropogenic one. Zoo Biol. 35:280–292, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.
    • The plight of the northern white rhinoceros (Ceratotherium simum cottoni): is there still hope to prevent extinction?

      Ryder, Oliver A.; Hermes, R.; Goeritz, F.; Durrant, Barbara S.; Stejskal, J.; Hrudy, J.; Vahala, L.; Loring, Jeanne F.; Hildebrandt, T.B.; Szentiks, C.A.; et al. (Leibniz Institute for Zoo and Wildlife ResearchBerlin, 2015)