Scientists have carried out the first successful embryo transfer in a southern white rhino using a method that could pave the way to saving its critically endangered northern cousin from extinction.
Key points: BioRescue scientists have successfully impregnated a southern white rhino using IVF
BioRescue scientists have successfully impregnated a southern white rhino using IVF The next step will see scientists try to repeat the feat with northern white rhino embryos to save the subspecies from the brink of extinction
The next step will see scientists try to repeat the feat with northern white rhino embryos to save the subspecies from the brink of extinction Researchers say this method could potentially be used in the future to save other endangered species of rhinos
The last male northern white rhino died in 2018. Just two female members remain now and they're under 24-hour armed protection at a sanctuary in Kenya.
But Najin and Fatu cannot carry a pregnancy to term, making the subspecies functionally extinct.
In a last chance at survival, scientists from the German-backed BioRescue consortium are turning to in-vitro fertilisation (IVF) to attempt to implant a lab-grown embryo in a related subspecies of southern white rhino.
The research team confirmed on Wednesday that the proof-of-concept procedure had produced a successful pregnancy of 70 days in a southern white rhino, with a well-developed male embryo of 6.4 centimetres.
The only two remaining northern white rhinos in existence are females. ( Supplied: BioRescue Project )
"We achieved together something which was not believed to be possible," Professor Thomas Hildebrandt, the project leader, said.
"That is really a milestone to allow us to produce northern white rhino calves in the next two, two and a half years," Dr Hildebrandt said.
The male embryo grew to 6.4 centimetres before the surrogate mother tragically died from an unrelated bacterial infection. ( Supplied: BioRescue Project )
The successful trial ended in "bitter" tragedy, he said, when the surrogate mother and her unborn calf were killed by an unrelated bacterial infection.
But the research team said they were confident the foetus would have survived the 16-month pregnancy period.
The next step will see scientists try to repeat the feat with northern rhino embryos made with eggs harvested from the surviving females and sperm preserved from two long-dead males.
To place the embryo in the surrogate, the team of conservationists use a sterile "teaser" bull rhino, whose approaches to the female indicate she is ready to conceive.
The team subsequently carry out the delicate operation in just under an hour with the surrogate under anaesthetic.
The size and delicate anatomy of the white rhinos means the embryo is implanted through the rectum and into the uterus.
Thomas Hildebrandt says the IVF method could potentially help save other endangered species of rhino. ( Supplied: BioRescue Project )
The trials were carried out using southern white rhino embryos to preserve what scarce genetic material is left from the northern species.
Susanne Holtze from the Leibniz Institute for Zoo and Wildlife Research said the BioRescue team have 30 fertilised eggs in freezers "waiting for their big day".
According to Dr Hildebrandt, the IVF method could potentially provide a model for saving other endangered species of rhino, such as the Sumatran rhino in South East Asia.
Northern white rhinos used to roam freely in several countries in east and central Africa, but their numbers fell sharply due to widespread poaching for their horns.