Scientists say they are closer to preventing the extinction of northern white rhinos, of which only two are known to still be alive.
According to a paper published in the journal Nature Communications, researchers have succeeded in creating embryos using frozen northern white rhino sperm and eggs from a southern white rhino, a closely related sub-species.
They plan to harvest the egg cells of the two surviving female rhinos soon and use preserved sperm to produce “pure” northern white rhino embryos.
Since the females, a mother and daughter called Najin and Fatu, are unable to bear offspring themselves, the embryos would be implanted in a southern white rhino surrogate.
In order to increase the supply of eggs and preserve the northern white rhino’s genetic diversity, scientists are also working on a second method that would coax frozen skin cells from deceased animals into becoming egg cells, a procedure that has already succeeded in mice.
Thomas Hildebrandt, of the Leibniz Institute for Zoo and Wildlife Research in Berlin, said researchers hope the first northern white rhino calf will be born in about three years.
“We are quite confident with the technology we have developed,” he said.
Saving the northern white rhino has become an international effort, with co-operation but also some rivalry among scientists and institutions around the world, including zoos in San Diego and Cincinnati.
Some experts have criticised the effort however, saying it comes too late.
“I have no doubt that its purely scientific merit is laudable and it might have some application to endangered species conservation in the future,” said Richard Kock, a conservationist at Britain’s Royal Veterinary College who has worked extensively in Africa.
“But I am afraid it is very much Nero fiddling after Rome is burning with respect to (northern) white rhino.”
Mr Hildebrandt insisted the effort is worthwhile. “The northern white rhino didn’t fail in evolution,” he said. “It failed because it’s not bulletproof. It was slaughtered by criminals which went for the horn because the horn costs more than gold.”
Northern white rhinos were once abundant across Central and East Africa, but conflicts and poaching wiped them from their natural habitat.
The rhino’s disappearance has left a void in the region’s ecosystem that could have significant impacts in the future, Mr Hildebrandt said. “We have the tools in our hands to correct that.”