Pregnancies following long luteal phases in southern white rhinoceros (Ceratotherium simum simum)

• Published in: Zoo biology 2020-03, Vol.39 (2), p.141-144
• Main Authors: Pennington, Parker M., Marshall, Kira L., Capiro, Jonnie M., Howard, Lauren, Durrant, Barbara S.
• Format: Article
• Language: English
• Subjects: Artificial insemination; assisted reproductive technology; Breeding; Brief Report; Ceratotherium simum simum; Ceratotherium simum ssp. simum; Embryos; estrous cycle; Estrus cycle; Females; freeze-thaw cycles; Genetic diversity; genetic variation; insemination; Offspring; Ovulation; Parturition; Phases; Population genetics; Pregnancy; progeny; Reproduction (biology); Reproductive technologies; Rhinocerotidae; Semen; southern white rhinoceros; Sustainability
• ISSN: 0733-3188; 1098-2361
• DOI: 10.1002/zoo.21529

All extant species in the Rhinocerotidae family are experiencing escalating threats in the wild, making self‐sustaining captive populations essential genetic reservoirs for species survival. Assisted reproductive technologies (ARTs) will become increasingly important for achieving and maintaining ex situ population sustainability and genetic diversity. Previous reports have shown that a large proportion of captive southern white rhinoceros (SWR) females are irregularly cyclic or acyclic, and that cycling females display two different estrous cycle lengths of approximately 30 or 70 days. It has been suggested that the longer estrous cycle length is infertile or subfertile, as no term pregnancies have been observed following long cycles. Here we report the achievement of two pregnancies following long luteal phases, using ovulation induction and artificial insemination with either fresh or frozen‐thawed semen. One female SWR conceived on the first insemination attempt and gave birth to a live offspring. A second female conceived twice in consecutive long cycles although the first embryo was resorbed by 33 days post‐insemination. A pregnancy from this female's second insemination is ongoing with expected parturition in November 2019. Whether prolonged estrous cycles in SWR are subfertile or infertile in natural breeding situations remains unclear. However, our findings demonstrate that the application of ARTs following prolonged cycles can result the successful establishment of pregnancies in SWR. Therefore, with ARTs, female SWR otherwise considered nonreproductive due to long estrous cycles may still have the potential for representation and contribution to the ex situ population. Research Highlights Two pregnancies were achieved following long luteal phases in two southern white rhinoceros females. We provide evidence that long luteal phases are not necessarily infertile or early pregnancy loss.