The Age of Extinction
The first successful embryo transfer in a southern white rhino paves the way for the use of techniques to save rare northern relatives
The critically endangered northern white rhino has been saved from extinction after scientists carried out the first successful white rhino embryo transfer.
After Sudan's last male northern white rhinoceros died in 2018, the species' disappearance seemed imminent. Only two sterile female northern white rhinos – Fatu and Najin – remain and are under 24-hour surveillance in a wildlife reserve in Kenya. But a new scientific advance means the mother and daughter may not be the last of their kind.
An international team of researchers from BioRescue – a federally supported consortium that aims to stop extinctions – has carried out the first successful embryo transfers in southern white rhinos, paving the way for the technique to be used in their rarer northern counterparts.
In September 2023, scientists at the Ol Pejeta Conservancy in Kenya transferred two southern white rhinoceros embryos into surrogate mothers, resulting in a successful pregnancy. While the method is commonly used on humans, horses and cows, it has never been used on rhinos before.
The first successful embryo transfer of a white rhinoceros. Sadly, the father and pregnant mother died after contracting another bacterial infection. Photo: JonJuarez/BioRescue
The father and pregnant mother died after contracting a rare, unrelated bacterial infection when the fetus was 70 days old. But researchers said the pregnancy was evidence that the technique can work.
Thomas Hildebrandt, leader of the BioRescue project and professor at the Leibniz Institute for Zoo and Wildlife Research, said the technique is an important step toward saving the northern white rhinoceros.
“This little baby is proof of everything,” he told the Guardian. “The sperm injection, the fertilization, the liquid nitrogen, the thawing – this has never been done in rhinos before. Everything could have failed.”
The fact that the process worked on rhinos was a major breakthrough, he said. In comparison: “Humans are simple!” We work with a mammal weighing two and a half tons.”
Scientists plan to implant the first northern white rhinoceros embryo by May or June of this year. The northern rhinoceros embryos were created from sperm from two now deceased males and eggs from Fatu. They are carried by a southern white rhinoceros surrogate in Kenya. There are only 30 embryos left, which are stored in liquid nitrogen at -196°C in Berlin (Germany) and Cremona (Italy).
The replacement rhino is injected with the embryo through its anus. If the 16-month pregnancy is successful, it would be the first northern white rhinoceros born since 2000. This could also pave the way for the protection of the Sumatran rhinoceros, of which there are around 40 animals in the wild.
Thomas Hildebrandt, BioRescue's project manager, holds the rhino embryo along with the rest of the team, November 29, 2023. Photo: JonJuarez/BioRescue
The researchers said they would carry out more embryo transfers if the first pregnancy appeared to be going well, meaning up to six northern white rhino calves could be born in a short period of time. Scientists said it was important for the calves to meet Fatu and Najin while the pair were still alive to learn how to behave like a northern white rhinoceros.
But even if multiple northern white rhino calves were born, they would not be genetically diverse enough to form a viable population, Hildebrandt said. The 30 surviving northern white rhinoceros embryos are all based on eggs from Fatu and sperm from two males.
If more mammals were born, researchers would try to use gene editing to improve the genetic diversity of future offspring, including extracting genetic material from museum samples.
Scientists plan to implant the first northern white rhinoceros embryo carried by a southern white rhinoceros surrogate mother in Kenya in May or June. Photo: Ami Vitale
“We go to the skulls and find genetic material,” Hildebrandt said. “Then we would use gene editing to introduce them into the population. We plan to visit all museums with northern white rhinoceros specimens. It’s not just a science experiment, we really want to bring it back.”
Last year it was announced that the southern white rhino population had increased for the first time since 2012, rising to 16,803 from 15,942 at the end of 2021. However, concerns remain about their long-term survival.
Erustus Kanga, director general of the Kenya Wildlife Service, said they were excited by the breakthrough to save the subspecies.
“The Kenya Wildlife Service is pleased to have been part of this journey for 13 years since the introduction of the northern white rhinos in 2009 and to have been part of the great initiative of the BioRescue Consortium for the last four years,” he said.
Return of the Rhino: Can We Save the Northern White from Extinction?
“This is a major milestone in the conservation of the northern white rhinoceros genetic lineage.”
Justin Heath, the CEO of Ol Pejeta Conservancy, said it was a major breakthrough for conservationists, but it was bittersweet after losing the replacement and the bull to the bacterial infection.
“Experiencing the world’s first rhino pregnancy following a successful surrogate transfer at Ol Pejeta Conservancy is a source of great pride for all of us,” he said. “We look forward to welcoming rhino calves from future surrogate mothers to the foothills of Mount Kenya soon.”
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