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During the past four decades, in vitro fertilization (IVF) has helped millions of people have children. Yet a successful IVF pregnancy had never been achieved in a rhinoceros—until now.
This scientific breakthrough is not just a triumph for reproductive technology. The most promising thing about it is that IVF could help save the critically endangered northern white rhino subspecies. The entire northern white rhino population consists of just two animals—both females—due to decades of aggressive poaching in pursuit of rhino horns.
Although Sudan, the world’s last male northern white rhino, died in 2018, there is still hope. Over the past four years, researchers from the BioRescue project have created 30 northern white rhino embryos using sperm from now-deceased males and oocytes (developing egg cells) harvested from Fatu, one of the subspecies’ last two surviving females. That is currently the entire genetic future of the northern white rhino, although BioRescue is also considering using a highly experimental technique that would create more northern white rhino sperm and eggs from stem cells.
Before implanting the very rare northern white rhino embryos, scientists needed to achieve the world's first rhino IVF pregnancy with a southern white rhino embryo (and surrogate mother). A rhino’s reproductive tract is around six feet (2 m) long, posing obvious challenges for embryo implantation, and the researchers needed 13 attempts to achieve a successful IVF pregnancy. It was a truly international effort, with the sperm being retrieved from a rhino in Austria and the egg cells from a rhino in Belgium. The in vitro fertilization took place in an Italian lab, and two embryos were then transferred to a female rhino in Kenya.
Unfortunately, the surrogate mother died 70 days into her pregnancy due to an unrelated bacterial infection, but the researchers consider the successful embryo transfer to be proof that it could be done again, this time with a lab-made northern white rhino embryo. Not wasting any time, BioRescue plans to use IVF to implant northern white rhino embryos in surrogate southern white rhinos later this year.
The last hope for northern white rhinos:
- Though northern and southern white rhinos are closely related, successful implantation and pregnancy would be especially groundbreaking as it would be the first use of IVF across subspecies. If these theoretical surrogate pregnancies result in live births, the northern white rhino subspecies could gradually repopulate and could even breed independently in 10 to 15 years.
- While there are clearly many “ifs” hanging over the project, the recent IVF success has given Susanne Holtze of the Leibniz Institute for Zoo and Wildlife Research reason to hope. “I think with this achievement, we are very confident that we will be able to create northern white rhinos in the same manner and that we will be able to save the species,” she told the BBC.
- Najin and her daughter, Fatu, the last two remaining northern white rhinos, live at the Ol Pejeta Conservancy in Kenya. Neither is currently capable of natural reproduction, but researchers hope that if northern white rhino calves are born as a result of IVF, they will be able to live with these older rhinos and learn their behaviors.