"There are only 2 northern white rhinos left on earth," a topic that has recently been on the hot search. In fact, as early as 2018, when the last male, the Northern White Rhino Sudan, died, there were only 2 Northern White Rhinos left on the earth.
Najin, 32, and her 21-year-old daughter, Fatu, are the only two remaining northern white rhinos. They are all females and can no longer reproduce naturally. If modern technology can't help them produce offspring, then we can only watch the northern white rhinoceros go extinct.
Now, the Northern White Rhinoceros is standing on the edge of a completely extinct cliff, waiting for an answer from modern technology.
In Sudan in 2010, there were still 8 northern white rhinos on Earth
They are pushed off a cliff
The Northern White Rhinoceros was once in a relatively safe position. Sixty years ago, there were more than 2,000 northern white rhinos in Africa, but by 1984 that number had plummeted to around 15 due to rampant poaching.
As a land animal second only to elephants in size, rhinos have few natural predators in the wild. There are now only five species left of these once widely distributed behemoths on Earth: the Sumatran rhinoceros, the black rhino, the Javan rhino, the Indian rhino and the white rhino – all of which are listed as critically endangered. Numerically, the white rhino is not yet endangered because, in addition to the only two northern white rhinos left, there are about 20,000 southern white rhinos, another subspecies of white rhinos.
The relatively safe southern white rhinoceros
But the northern white rhino is not as lucky as its relatives who live in the south. Due to illegal hunting, in 2008, the northern white rhino was declared extinct in the wild, leaving only 8 northern white rhinos in captivity in the zoo.
In 2009, dvůr Králové Zoo in the Czech Republic sent four northern white rhinos to the Ol Pejeta Nature Reserve in Kenya: the female Nagin and Fatu and the male Suni and The Sultan.
Hopes are high on Africa's warm climate and vast grasslands, perhaps this pristine environment will help the northern white rhinos mate successfully and breed offspring.
Unfortunately, Nagin and Fatu did not become pregnant. A 2014 health review showed that they were not suitable for procreation: Fatu had a uterine disease; Nagin had a leg injury and complications associated with pregnancy.
Nagin and Fatu in the O Pejeta Nature Reserve
During this decade, the few other remaining northern white rhinos in the zoo have also died – Neasri in 2011, Angalifu and Suni in 2014, Nabire and Nola in 2015...
Then there's Sudan, who left in 2018 — the only lone northern white rhino mother and daughter left on Earth.
Can technology save them?
There is no way out of natural breeding, and the only way to save the northern white rhino can rely on assisted reproduction, that is, "IVF".
When several male northern white rhinos were still alive, researchers had already collected their sperm and frozen them.
If we can obtain the eggs of Nagin and Fatu, fertilize them in vitro, and then transfer the successful embryos into the womb of the surrogate mother rhinoceros, we still have a chance to welcome the northern white rhino newborn.
But this series of technologies is not simple.
A map of local anesthesia before egg retrieval, after which it will be anesthetized by general anesthesia
In terms of egg retrieval alone, researchers must first anesthetize the rhino and then retrieve egg cells from the ovary as quickly and accurately as possible; if the anesthesia is too long, or if the blood vessels near the ovaries are accidentally injured, it will cause damage to the rhinos.
The two surviving northern white rhinos are too precious, and in order to ensure that they are foolproof, the researchers can only grope for other rhinos first. The Southern White Rhinoceros, which is the closest to the Northern White Rhinoceros and is at a relatively safe level for the time being, has naturally become the first choice for researchers.
Since 2014, at least 15 European zoos have given the green light to the northern white rhino's egg retrieval technology, willing to let their own southern white rhino act as guinea pigs. After determining that the technique was feasible, in August 2019, researchers finally performed the first egg retrieval of the northern white rhinoceros.
The egg retrieval process went smoothly, and after nearly two hours of anesthesia, both northern white rhinos also woke up. A total of 10 active egg cells were retrieved, which were quickly cryopreserved and sent to a helicopter waiting nearby; after three transits, they were sent to a laboratory in Italy.
After the egg retrieval surgery was completed, the photo was posted on Twitter at the O Pejeta Nature Reserve: "Nagin and Fatu just took a bath in the mud and it feels good!" ”
Of these 10 egg cells, 7 are in a mature state that can be fertilized. At the same time, the researchers revived previously preserved northern white rhinoceros sperm and injected sperm into egg cells to complete in vitro fertilization.
After half a month of culture and observation, the researchers announced that 2 of the 7 fertilized eggs had successfully developed into embryos. A few months later, they underwent another egg retrieval operation, this time obtaining 1 surviving embryo.
The 4 egg cells of Fatu and the 3 egg cells of Nagin have reached a mature state that can be fertilized
Race against time
Fast forward to 2020, when a sudden outbreak disrupted the plan; it wasn't until the end of the year that researchers managed to get 14 eggs from Fatu and grow 2 surviving embryos.
Unfortunately, Fatu's mother, Nagin, was unable to provide egg cells this time, and the egg cells previously taken from her body did not succeed in producing embryos, and age or health problems could affect her reproduction.
So far, we have 5 northern white rhinoceros embryos. These 5 hard-won hopes are currently cryopreserved in liquid nitrogen – they are still waiting for the embryo transfer technology to mature.
If sufficiently sophisticated techniques are available, these embryos will be transferred into the surrogate female southern white rhinoceros. At present, researchers are actively experimenting with this technology.
They will observe and predict the estrus cycle of the surrogate female southern white rhino, trying to find the best time for embryos to move in — but these attempts are just getting started, as Richard Vigne, head of the O.P. Geta Nature Reserve, puts it, "We are still a long way from achieving this goal." ”
At the same time, under the premise of ensuring the health of Fatu and Najin, the researchers will continue to take eggs for them and cultivate more northern white rhino embryos, so as not to be helpless when future transfers fail.
Late last year, scientists retrieved eggs from northern white rhinos in Kenya
However, even if surrogacy is successful, genetic diversity is still a major problem. Just as Nagin and Fatu, the daughters and granddaughters of the Sultan, respectively, the sperm and egg cells used for assisted reproduction actually come from a limited number of northern white rhinos that are not far from relatives. The resulting pups may be the product of inbreeding, and the genetic diversity is too low to continue to reproduce a stable population.
To solve this problem, we may rely on stem cell technology to induce somatic cells into pluripotent stem cells, which then develop into germ cells and reproduce baby rhinos. In 2018, the San Diego Zoo in the United States analyzed their frozen northern white rhinoceros cells and found that the samples had a sufficiently high genetic diversity; if they could be used to make new northern white rhinos, they might save these endangered behemoths.
However, the premise of all this is that this more challenging stem cell technology can be successfully implemented.
In February 2019, scientists injected an anesthetic into a polish southern white rhino and then moved the southern white rhino embryo into her body. However, we have not found follow-up reports on this embryo transfer, which appears to have failed
Scientists and the Northern White Rhinoceros are in a race against time. If the northern white rhino newborns in the laboratory can be born before Nagin and Fatu die, the baby rhinos can also follow them to learn ancestral survival skills and learn how to become a northern white rhinoceros.
The greed and arrogance of human beings have pushed the Northern White Rhino and scientists into this race against time. This time, can we outperform? Will the planet be able to return to the 3rd Northern White Rhino?
Hopefully, modern technology can bring miracles.