The critically endangered northern white rhino could be saved from the brink of extinction after scientists performed the first successful embryo transfer into white rhinos.
After the last male northern white rhino, Sudan, died in 2018, the disappearance of the species seemed imminent. Just two barren female northern white rhinoceros – Fatu and Najin – remain, and are under 24-hour armed protection at a conservation 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 consortium, backed by the German government, which aims to stop extinctions – carried out the first successful embryo transfers in southern white rhinos, paving the way for the technique to be used for their rarer northern counterparts.
In September 2023, scientists transferred two southern white rhinoceros embryos in surrogate at the Ol Pejeta Conservancy in Kenya, resulting in a successful pregnancy. Although commonly used in humans, horses and cows, the method has never before been used in rhinos.
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 proof the technique could work.
Thomas Hildebrandt, the BioRescue project leader and a professor at the Leibniz Institute for Zoo and Wildlife Research, said the technique was a key step in saving the northern white rhino.
“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 before for rhinos. All of this could have failed.”
For the process, working in rhinos was a major breakthrough, he said. In comparison: “People are simple! We are working with a two and a half ton mammal.”
By May or June this year, scientists plan to implant the first northern white rhino embryo. The Northern rhino embryos were created with sperm collected from two now dead males, and eggs collected from Fatu. They will be carried by a southern white rhino surrogate in Kenya. Just 30 embryos remain – stored in liquid nitrogen at -196C in Berlin, Germany and Cremona, Italy.
The surrogate rhino is injected with the embryo through its anus. If the 16-month pregnancy is successful, it will be the first northern white rhino born since 2000. It could also pave the way for the conservation of the Sumatran rhino, which has around 40 in nature.
Researchers said they would do more embryo transfers if the first pregnancy appeared to be going well, meaning as many as six northern white rhino calves could be born in a short period of time. Scientists said it would be important for the calves to meet Fatu and Najin while the pair were still alive, to learn how to behave like a northern white rhino.
However, even if several northern white rhino calves are born, they will not be genetically diverse enough to produce a viable population, Hildebrandt said. The 30 surviving northern white rhino embryos are all based on eggs from Fatu and sperm from two males.
If more mammals are born, researchers said they will try to use gene editing to improve the genetic diversity of future offspring, and also to take genetic material from museum specimens.
“We go to the skulls and find genetic material,” Hildebrandt said. “Then we will use gene editing to put them into the population. We plan to go to all the museums with northern white rhino specimens. It’s not just a science experiment, we really want to bring it back.”
Last year it was announced that southern white rhino populations increased for the first time since 2012, which rose from 15,942 at the end of 2021 to 16,803. But concerns remain about their long-term survival.
Erustus Kanga, the Director General of Kenya Wildlife Service, said they were delighted with the breakthrough to save the subspecies.
“Kenya Wildlife Service is delighted to have been part of this journey for the past 13 years, since the northern white rhinos were brought to Kenya in 2009, and to be part of the major initiative of the BioRescue consortium over the past four years, ” he said.
“This is a major milestone in the conservation of the genetic lineage of the northern white rhino.”
Justin Heath, the CEO of Ol Pejeta Conservancy, said it was a major breakthrough for conservationists, but was bittersweet after losing the surrogate and bull to the bacterial infection.
“Having the world’s first pregnancy in a rhino after a successful surrogate transfer on Ol Pejeta Conservancy is a point of great pride for all of us,” he said. “We look forward to welcoming future surrogates’ rhino calves soon under the foothills of Mount Kenya.”
