Scientists have performed the world’s first successful embryo transfer in white rhinos, a feat which can save northern white rhinos that are on the brink of extinction, according to media reports. White rhinos are the second-most largest land mammal, and are also known as square-lipped rhinos, because they have a square upper lip with almost no hair. Northern and southern white rhinos are the two genetically distinct subspecies of white rhinos, and only two northern white rhinos remain on the Earth, making it a critically endangered species.
These are two infertile females, named Fatu and Najin, who live under 24-hour armed protection at a conservation reservation in Kenya called the Ol Pejeta Conservancy. Also, Fatu and Najin are a mother-daughter duo, according to a report by The Guardian.
The last male northern white rhino, Sudan, died in 2018. Fatu and Najin need not necessarily be the last of their kind to live on the planet because now, scientists have successfully performed the first embryo transfers in southern white rhinos. These scientists are from BioRescue, a non-profit consortium whose mission is to save northern white rhinos.
Now, a question arises that if they performed the experiment successfully in southern white rhinos, how will the achievement help northern white rhinos? The answer to this doubt is that if in-vitro fertilisation (IVF) can successfully be performed in southern white rhinos, it is not long before the same experiment can be conducted in their rarer northern counterparts to save the critically endangered species.
As part of the experiment performed in September 2023, two southern white rhino embryos were transferred into surrogates at the Ol Pejeta conservatory. Only one of them became pregnant.
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IVF is commonly used in humans, cows, and horses, but had never been used in rhinos earlier. According to the Guardian report, the father and the pregnant mother contracted a rare, unrelated bacterial infection, and died when the foetus was 70 days old. The researchers have said that the successful pregnancy is testament to the fact that IVF can work in white rhinos.
The name of the surrogate mother was Curra, according to an article by The National Geographic. Jan Stejskal of the BioRescue project said that the successful pregnancy provides the essential “proof of concept” that IVF can help northern white rhinos, despite the fact that Curra died a couple of months into her 16-month pregnancy from an unrelated bacterial infection.
What will be done next to save northern white rhinos?
According to the article, BioRescue aims to soon implant a northern white rhino embryo into a southern white rhino surrogate mother and since the two subspecies are similar enough, the embryo will be likely to develop, the researchers have said.
Due to constant poaching, and a huge demand for the horn of northern white rhinos for medicinal applications and carvings, the species has approached the brink of extinction.
Ami Vitale, a National Geographic Explorer, expressed surprise at the fact that northern white rhinos, which look prehistoric, and had survived for millions of years, could not survive “us”, which refers to humans.
In order to ensure that northern white rhinos do not become extinct, BioRescue has used preserved sperm and eggs removed from the younger of the two remaining females to create about 30 preserved embryos, according to Thomas Hildebrandt, the head scientist of BioRescue. Fatu is the younger one of the two female northern white rhinos living on the Earth. The two males from whom the sperms were gathered are now dead.
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The experts aim to re-introduce northern white rhinos into the wild several years later, if IVF is shown to be successful in this subspecies.
As part of the next phase of their plan, the BioRescue experts will implant one of their limited number of northern white rhino embryos into a southern white rhino surrogate mother, according to the article. Stejskal said the team intends to perform this experiment within the next six months.
The eggs have been preserved inside liquid nitrogen at minus 196 degrees Celsius in Berlin, Germany, and Cremona, Italy. The surrogate southern white rhino female inside whose womb the embryo will be injected has also been selected.
When the female will be in estrus, which means when she will be ready to mate, the embryo will be injected into her body through her anus, and if the 16-month pregnancy is successful, the baby will be the first northern white rhino to be born since 2000.
The first embryo transfer of a northern white rhino will be performed in May or June this year, and if the transfer is successful and the pregnancy appears to go well, the experts will perform more embryo transfers. In order to learn how to behave like a northern white rhino, the IVF calves, if born, must meet Fatu and Najin while they are still alive.
The success of this technique will pave the way towards ensuring that other critically endangered rhino species, such as the Sumatran rhino, and the Asian Javan rhino, can be saved from extinction.
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