Scientists are planning to use a southern white rhino as a surrogate in efforts to save the northern white rhino that is facing extinction.
Sudan, the only surviving male northern white rhino, was declared unable to sire offspring due to his old age.
Now, scientists will harvest ova from two northern white rhinos at Ol Pejeta Conservancy in northern Kenya, which will be fertilised in a laboratory in Italy and then implanted into a southern white rhino.
The two females, Fatu 28, and Najin 17, are thought to be too old to carry a pregnancy.
"Although the northern white rhino females showed signs of ovulation, no confirmed pregnancies occurred," the conservancy said.
Last December, veterinarians, conservationists and wildlife managers from the Czech Republic, Kenya, the UK and South Africa met to discuss the groundbreaking procedure.
Under the supervision of the Kenya Wildlife Service, the ova pick-up is expected to be conducted on Najin and Fatu later this year. If successful, their eggs will be shipped to a laboratory in Italy.
The researchers hope to mature an embryo using northern white rhino sperm currently stored in Berlin. The embryo will then be implanted in the southern white rhino female at Ol Pejeta.
In 2016, scientists began retrieving and storing eggs from southern white rhino females in European zoos, and fertilising them in vitro. They then harvested eggs from Najin and Fatu.
"The surgery required to harvest these eggs carries essential dangers and will have to be conducted in the field. The fate of the northern white rhino subspecies depends on this operation going smoothly," the conservancy said.
The conservancy's chief executive officer Richard Vigne told The EastAfrican last week that a male southern white rhino christened Kingi, which had been placed together with five southern white females on the more than 700-acre ranch, was moved to "ensure that all surrogates will be 'empty' and ready for receiving the embryos".
Sudan, 45, gained international attention in 2016 when a team of scientists were trying to harvest its sperm in order to preserve the species.
Since last December, Sudan has been under medical care from veterinarians from around the world, and had responded well to treatment, but caretakers are concerned about his frail health.
He has now developed an infection on his back right leg that won't heal completely.
"Sudan has been suffering from bedsores as his mobility decreased, one of which had become infected. We are treating his wounds twice a day to avoid the risk of infection, and they are getting better. The sores are being made worse because he lies down too much," Ol Pejeta spokeswoman Elodie Sampere said.
"Recently, a secondary and much deeper infection was discovered beneath the initial one. This has been treated, but, disturbingly, the infection is taking long to recover. We are very concerned about him especially given his advanced age," said the conservancy.