Living Animals in White Rhino Breeding Program: One

Hopes of saving the northern white rhinoceros now rest on a sole female, some frozen sperm, and a dozen embryos. There are just two northern white rhinos alive—females Najin and Fatu of Kenya's Ol Pejeta Conservancy—whose eggs were extracted, then inseminated with frozen sperm from dead males as part of an unprecedented breeding program. Since 2019, 12 viable embryos have been produced from Fatu's immature eggs, known as oocytes, and sperm from a male named Suni who died at Ol Pejeta in 2014. The embryos are now awaiting transfer to a southern white rhino surrogate as neither Najin nor Fatu can carry a pregnancy to term, per AFP and Christian Science Monitor. Moreover, any additional eggs will have to come from Fatu, in her early 20s, as her 32-year-old mother has now been retired.

The egg extraction is a risky procedure requiring anesthesia, and during a recent sedation, officials found Najin didn't have enough promising oocytes for extraction. "Weighing up risks and opportunities for the individuals and the entire species rendered this decision without an alternative," says scientific consortium BioRescue. Jan Stejskal of consortium partner Safari Park Dvur Kralove in the Czech Republic, where Najin and Fatu were born, notes Najin "will remain a part of the program, for example by providing tissue samples for stem cell approaches, which can be performed with minimal invasion," per AFP. Many challenges remain in rescuing the species from extinction, Ol Pejeta chief Richard Vigne told the outlet in July, noting, "No one is going to pretend that this is going to be easy." (More rhinoceros stories.)