Frozen sperm from deceased males remains.
Egg cells can still be collected from Fatu.
And stored tissue from northern white rhinos has given scientists another possible route toward increasing genetic diversity in the future.
That difference—between functionally extinct and absolutely extinct—is where one of the most ambitious reproductive science projects in conservation history has emerged.
Turning to IVF
After natural reproduction became impossible, scientists began pursuing assisted reproductive technologies.
The principle resembles human IVF, although the scale and complexity are dramatically different.
Scientists collect immature oocytes, or egg cells, from a female rhino.
Those eggs are matured in a laboratory.
They are then fertilized using sperm that had been collected and frozen from northern white rhino males before they died.
If fertilization succeeds and the embryo develops normally, it can be cryopreserved.
Eventually, the embryo can be transferred into a surrogate mother.
Because Najin and Fatu cannot carry pregnancies, scientists plan to use female southern white rhinos as surrogates.
Southern white rhinos are closely related to northern white rhinos and remain far more numerous.
BioRescue began collecting eggs from Najin and Fatu in 2019.
Later, egg collection from Najin was discontinued following ethical and veterinary assessments, leaving Fatu as the only living donor of natural northern white rhino oocytes.
The work is exceptionally difficult.
Rhinos are enormous animals, and reproductive procedures require sophisticated veterinary techniques, anesthesia, ultrasound guidance and specialized equipment.
Egg cells collected in Kenya must be transported to laboratories where fertilization and embryo development can be performed.
Even producing a healthy embryo is only one stage.
The embryo must then successfully implant in a surrogate female.
A pregnancy must continue normally.
And after a gestation lasting roughly 16 months, a healthy calf must be born.
Each step contains uncertainty.
A Breakthrough Scientists Had Never Achieved Before
Despite the challenges, researchers have made progress that would once have seemed improbable.
Scientists working with BioRescue demonstrated that viable northern white rhino embryos could be created.
But one enormous question remained:
Could a rhino become pregnant after an embryo created through IVF was transferred into her?
Researchers tested the method using southern white rhinos.
In 2023, the team achieved the first known pregnancy in a rhinoceros produced through IVF and embryo transfer.
The embryo was from a southern white rhino and was transferred into a southern white rhino surrogate.
The pregnancy proved that the basic reproductive technology could work.
The surrogate later died following an unrelated bacterial infection, but an examination revealed that the transferred embryo had successfully implanted and developed.
That result was scientifically crucial.
It demonstrated that embryo transfer could produce a genuine rhino pregnancy.
The next challenge was to repeat the process using a pure northern white rhino embryo.
Thirty-Nine Embryos—and Counting
Progress has continued.
By August 2025, BioRescue reported that researchers had produced 38 pure northern white rhino embryos.
Scientists had also begun transferring northern white rhino embryos into southern white rhino surrogate mothers.
Early transfer attempts did not result in a lasting pregnancy.
Then, in early 2026, researchers collected additional egg cells from Fatu and successfully produced another embryo.
That brought the total number of pure northern white rhino embryos created to 39, according to an April 2026 update from Ol Pejeta Conservancy.
The same update reported that several northern white rhino embryo transfer attempts conducted in 2025 had not yet produced a long-term pregnancy.
Researchers have therefore continued refining the procedure and identifying additional southern white rhino females as potential surrogate mothers.
As of 2026, no northern white rhino calf produced through the program has yet been born.
But the existence of 39 embryos represents something remarkable.
When Sudan died in 2018, the possibility of another northern white rhino birth seemed almost impossible.
Today, that possibility exists inside frozen embryos stored through reproductive technology.
The Genetic Problem
Even if the IVF program succeeds, however, producing a few calves will not automatically restore a healthy population.
A species—or subspecies—needs genetic diversity.
If all future northern white rhinos descend from only a tiny number of closely related animals, inbreeding could create serious long-term problems.