Saving A Species: Two Of Seven Fertilized Northern White Rhino Eggs Result In Embryos

Northern white rhino keeper, James Mwenda, checks on Najin, one of the last two northern white rhino son the planet. Najin lives at Ol Pejeta Conservancy in Kenya. Ami Vitale

Scientists working urgently to save the northern white rhino species have come one step closer, this time successfully creating two northern white rhino embryos soon-to-be transferred into a surrogate mother.

It comes after an international consortium of scientists fertilized seven eggs harvested from the last two remaining females of the species, mother-daughter duo Najin and Fatu, both of whom are too old to carry their own offspring.

“Today we achieved an important milestone on a rocky road which allows us to plan the future steps in the rescue program of the northern white rhino,” said Thomas Hildebrandt from Leibniz-IZW in a statement.

The two embryos were created using eggs from Fatu, the youngest of the two, and frozen sperm from the last-deceased northern white rhino male, Suni, wrote Ol Pejeta. Najin’s eggs were injected with Saut’s sperm, but it was too poor of quality to be successful. Though one of Najin’s eggs initiated segmentation, neither ultimately made it to a viable embryo. 

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Just before the last northern white rhino male fell ill and died in 2018, reproductive biologists and zoologists collected sperm cells and DNA in an unsuccessful attempt to breed a northern white rhino hybrid. (Scientists were so desperate in the months preceding his death that they even created a mock Tinder profile complete with some of his best photos.) The embryos will now be stored in liquid nitrogen and transferred to a closely related southern white rhino female surrogate in the near future. The new technology may have broader implications for other species facing similar plights across the planet.

“Five years ago it seemed like the production of a northern white rhino embryo was [an] almost unachievable goal – and today we have them. This fantastic achievement of the whole team allows us to be optimistic regarding our next steps,” said Jan Stejskal, director of Communication and International Projects from Dvůr Králové Zoo, where Najin and Fatu were born.

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In the coming months, Stejskal says scientists will be determining ways to “optimize the process of transfer and following the development of an embryo in a body of a surrogate mother” in cooperation with European zoos. Southern white rhinos are closely related to their northern cousins and have seen population increases in recent years following protections across much of Africa. Just last month, a southern white rhino baby named Edward was born after being conceived through artificial insemination.

The project is part of the initiative “BioRescue” that aims to advance assisted reproduction technologies (ART) and stem cell-associated techniques to prevent the complete extinction of northern white rhinos. A subspecies of the white rhino, Ceratotherium simum cottoni, were driven to extinction in the wild by poaching and other human activities. The number of individuals left in the world dropped to just two, Fatu and Najin, after the last male died in 2018.   

Ol Pejeta Conservancy
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