At 45, Sudan was older than the average Tinder user, but that didn’t stop hundreds of people from swiping right to check him out. Sudan wasn’t looking for a match, exactly. It was way too late for that. His caretakers at Ol Pejeta Conservancy in Kenya thought a Tinder profile would help draw attention to his species, the critically endangered northern white rhinoceros.
“I don’t mean to be too forward, but the fate of my species literally depends on me,” his profile said.
The plea was a bit of hyperbole, but there was truth in it. Users who swiped right were taken to a page where they could learn more about Sudan and donate to a campaign to save his species. He was the last male standing, the final specimen of the iconic, 2.5-ton behemoths that once roamed throughout central Africa in large numbers. Poachers had hunted the northern white rhino nearly to extinction. The only animals left were in zoos and animal conservancies in Europe and Africa.
But ultimately, the Tinder profile was not enough. Sudan, who suffered from a host of age-related illnesses, died on March 19, 2018. He was survived by his daughter, Najin, and granddaughter, Fatu, who lived nearby. They are the last of his species; his genetic line lives on only as long as they do. Yet Sudan’s descendants are too frail to maintain a pregnancy.
But hope may not be lost for the northern white rhinoceros. Cutting-edge reproductive technology — the type that has enabled thousands of families to conceive children — is being applied to endangered species like Sudan’s family. The future of the species now rests entirely on the most advanced reproductive technologies science has to offer: in vitro fertilization, surrogacy and stem cell development. If scientists are successful, the next generation of northern whites will begin their development in petri dishes, where they will grow for two weeks before finally being implanted in surrogate mothers.
In his youth, Sudan had plenty of chances to mate, though none succeeded. But before he retired as a potential sire, scientists harvested some of his sperm. In May 2018, scientists published research showing that Sudan’s sperm could be combined with eggs harvested from southern white rhino females, and that they could grow into blastocysts, an early embryo that represents the first stage of cell differentiation. The blastocysts grew for 13 days before researchers froze them for safekeeping. If these blastocysts can be implanted into surrogate mothers, they may eventually grow into rhino fetuses, and ultimately new calves.
If scientists are successful, distant descendants of Sudan may once again roam the plains of sub-Saharan Africa. If not — and the odds of failure seem high — Sudan will be remembered as an endling, a last of his kind, an emblem not just of Africa but of the Anthropocene. But in their efforts to save the northern white rhino, scientists are learning what it takes to save such enormous land mammals, and moreover, what it means to try.
Return of the Rhinos
White rhinos as an umbrella group are threatened, but they are still the most common of the world’s five remaining rhino species. Poachers are their primary adversary, killing them at the rate of three per day for use in horn products in Southeast and East Asia, including China and Vietnam. Rhino populations began to plummet in the 1970s, and their numbers plunged dramatically starting in 2008, when demand from Chinese buyers led to a sharp increase in poaching.
The northern white rhino is one of two subspecies along with their counterparts, the southern white rhinos. Northern whites, Sudan’s ancestors, historically lived in what’s now Congo, Uganda, South Sudan and the Central African Republic. Southern whites covered the area now encompassing Namibia, Botswana, Zimbabwe and parts of South Africa. The subspecies are separated by 100,000 years of evolution, according to genetic research, but they may have occasionally interbred at times after the last ice age.
And it’s not all bad news. The southern white rhino has made a remarkable comeback in the wild after successful captive breeding programs and conservation efforts, and they now number around 20,000. Zoos and conservatories in the United States and Europe have even developed successful artificial insemination programs for the southern whites.
But efforts to breed captive northern white rhinos have been less fruitful, says Jan Stejskal, director of the Dvur Kralove Zoo in the Czech Republic, where Sudan lived for many years and where Najin and Fatu were born. Efforts to breed captive northern white rhinos began in the 1980s, but resulted in only a couple of calves, he says.
“In 2007 or 2008, we started to think about what else we could try to prompt the breeding,” Stejskal says. “We thought maybe we could send the last animals capable of reproduction back to Africa — to send them to their original habitat, or at least habitat that would be similar.”
So, in December 2009, Sudan, Najin, Fatu and a male named Suni were transported from the Czech Republic to Ol Pejeta, a 90,000-acre conservancy in central Kenya. A Czech company called Stafi built wooden crates capable of bearing the rhinos, and Ol Pejeta staff constructed bomas, a commonly used animal pen used throughout central and southern Africa. The rhinos had a few weeks of crate training to acclimate them to their journey on a cargo plane.
Then, on Dec. 19, 2009, the four animals were loaded onto a Martinair airliner, which made a special stop in Prague during a regular Amsterdam-Nairobi cargo flight. Once airborne, the rhinos’ journey to their home grounds would take seven and a half hours. After they landed, the rhinos were transported by DHL trucks to Ol Pejeta. (The carrier offered a discount, according to records of the proceedings.) Twenty-six hours after they left Dvur Kralove, the rhinos were moved into their new bomas.
For Sudan, the journey to the grassy preserve where he would ultimately live out his days mirrored a trip he had taken some four decades earlier, when he was around 2 years old.
A Savanna Behind the Iron Curtain
In March 1975, Sudan and five other northern white rhinos were captured in what is now the country of South Sudan. After a six-month journey, they arrived at Dvur Kralove Zoo, then known as the East Bohemian Zoological Garden in the Soviet nation of Czechoslovakia.
At that time, it was a prominent destination for tourists as well as a zoological research station. The zoo’s longtime director, Josef Vágner, was obsessed with African animals. When he took over the zoo in 1965, he wrote to the ambassadors of Czechoslovakia and several African nations, hoping to obtain a visa to visit the continent. The only ambassador who replied was from Uganda, according to Stejskal, who has Vágner’s diaries. During the next two decades, Vágner would make eight expeditions to Africa and import more than 2,000 animals, mostly ungulates including zebras, giraffes, antelope, elephants — and rhinos.
“He had a dream that he would build something like a small Africa in the area where he lived,” Stejskal says. “For people behind the Iron Curtain, it was like a miracle. We could not travel. Even going to Poland or Russia was problematic. But now in this land of gray, you have this place where you have elephants, giraffes, unbelievable number of zebras, and other animals.”
By 1975, Dvur Kralove Zoo officials were breeding large numbers of animals. Vágner planned to build a big enough population to eventually return them to Africa. Even in the 1960s, their habitat was diminishing. In a 1967 diary entry from Uganda, Vágner argued that taking animals from Africa to European zoos was humane and justifiable as a means to protect them. As he saw it, “habitat for wild animals in Africa was diminishing, and soon they will be extirpated from large areas,” Stejskal wrote. The zoo’s efforts to save the white rhino are an extension of this legacy, he added.
“We are convinced that if we have the techniques at our fingertips, we really should try to utilize it for the good of the northern white rhino,” he wrote.
After the journey back to Africa, Sudan and another male rhino attempted to mate with the few remaining females in 2011 and 2012. Caretakers watched and waited. A rhino’s gestation period is 16 months, so by 2014, it was clear there would be no baby. That fall, Suni died, at age 36. Crestfallen, Stejskal traveled to Ol Pejeta, and caretakers ran a suite of tests on Sudan, Najin and Fatu. Fatu showed pathological changes in her uterus that suggested she may have been pregnant and miscarried. Nijan’s reproductive organs were fine, but at 36 she is elderly for a rhino, and she has some problems with her hind legs that would make her unable to carry a 220-pound fetus.
The research team knew they were running out of options, and they had already started to prepare. Researchers at the Leibniz Institute for Zoo and Wildlife Research in Germany, as well as an animal reproductive technology lab called Avantea in Cremona, Italy, were working toward in vitro fertilization. If the researchers could harvest healthy egg cells from female rhinos, they could then inject sperm previously collected from Sudan and later frozen. The rhino embryo could then be implanted into a surrogate mother, a southern white rhinoceros, who would later give birth to a hybrid calf.
During IVF in humans, a woman’s hormone levels and egg development are carefully monitored with blood tests and ultrasounds, and egg retrieval and fertilization is precisely timed. But for a rhino, the effort is much more difficult.
“We cannot monitor the whole process, so we have to go sort of blind,” says Cesare Galli, a veterinarian and embryologist at Avantea. “We give it a little hormonal stimulation, but we find it is always unpredictable. Not every animal responds in the same way.”
What’s more, female white rhino ovaries are about 6.5 feet inside her body, so the animal must be under anesthesia for the procedure. Technicians spent two years refining their techniques, Galli says.
At the San Diego Zoo, reproductive scientists successfully impregnated two southern white rhino females after years of painstaking effort, says Parker Pennington, a reproductive scientist at the zoo who works on northern white rhino conservation. The zoo’s female rhinos receive vaginal ultrasounds twice a week, and she attributes the pregnancies to the trainers’ and physicians’ efforts to bond with the rhinos.
“We don’t want them to see us as any different. When we show up, we don’t want them to be like, ‘Oh no, it’s them!’ The trainers made a great point to include us in the relationship building, so we are a positive part of their everyday landscape,” she says. “Rhinos are very curious by nature anyway, which is great because it makes them willing to participate and go investigate something.”
Rather than subject Najin and Fatu to invasive procedures, the researchers instead collected eggs from 12 southern white rhinos, resulting in 83 eggs. Then the eggs were fertilized with semen collected and frozen years earlier from three northern white rhino bulls, including Sudan. In some cases, the semen is poor quality, and precious little remains. But Galli and his team managed to fertilize some of the eggs using a technique called intracytoplasmic sperm injection, or ICSI, where a sperm cell is directly implanted inside the egg’s cell wall. A mild electric shock helps activate the egg during this procedure, prompting it to absorb the sperm cell’s chromosomes and form a zygote. The latter is a fertilized egg, containing a combination of DNA from the sperm and the egg. Ultimately, four of these early embryos developed into blastocysts, or embryos that are beginning to differentiate.
Some of the embryos were used to derive stem cell lines, which may also help to revive the species. Recent, early research has shown that stem cells can be used to form the precursors of sperm and egg cells, which can later be combined to form a new embryo. Producing new eggs and sperm from stem cells would add genetic diversity to the lab-grown northern white rhino population, potentially making recovery more likely.
The experiment was the first time a rhino embryo created in a lab has reached the blastocyst stage, according to scientists at the San Diego Zoo who were not involved in the work. Pennington says it shows some form of conservation may still be possible.
“We don’t have another option for northern whites at this point,” she says.
The team has produced three new embryos since their research was published last year, and three remain, Galli says. The blastocysts have now been frozen.
A Captive Future
Meanwhile, Galli and others plan to travel to Kenya in 2019 to harvest eggs from Najin and Fatu, and to combine the eggs with frozen sperm from northern white rhino males.
Even if that process works — if researchers can harvest eggs from aging Najin and infertile Fatu, create embryos that develop into healthy blastocysts — they would have to be implanted in a southern white rhino surrogate mother. But no one knows yet if a southern white can carry a northern white fetus to term. The animals’ distinct genetic lineage may pose problems. And if she successfully delivers a calf, the baby rhinos could still be hybrid animals incapable of their own reproduction.
“This is another issue; they will be different animals. They will be born to a southern white female, so not exactly the same species,” Galli says.
Researchers have been trying assisted reproductive technology for species conservation since these tools were invented in the 1970s, noted conservation scientists Terri Roth and William Swanson of the Cincinnati Zoo, who were not involved in the new research. “However, the development of (assisted reproductive technologies) for wildlife species has not lived up to early expectations,” they wrote in a commentary that accompanied the IVF success story. To date, assisted reproduction has worked on just three species: the black-footed ferret, the giant panda and the Asian elephant.
If they’re successful here, conservationists aren’t sure what life would be like for the rhino. They would be born in captive conditions and would need training before they could be reintroduced to the environment. They would never know life as a solitary wandering behemoth; they would never know the lived experience of their ancestors.
Pennington says zoo trainers would work with the new hybrid animals to teach them typical behaviors, recognizing that captivity is not the same experience.
“Captivity is not a bad place. It is different. But from our view, we think our animals are well cared for,” she says. “They need to know how to be their species, but we recognize that. We make every reasonable effort to provide species with the things that make them, them.”
Stejskal, who knew Sudan for 11 years, says the captive rhinos were already different from the beasts from which they descended.
“They say Sudan was a character, and I can confirm this. It is hard to say that an animal likes people, just because he is so calm, and has no problem being close to me, and to be scratched on the back or patted on the back,” he says. “But he walked slowly. He was not aggressive at you. He was not like some animals, doing anything to make you happy, but he had his own way. He was calm. And I would say he was nice to his caretakers, but with dignity. You felt his dignity.”
Stejskal says the rhino conservation effort may be more successful than other prominent assisted-reproduction efforts, notably wooly mammoth resurrection using surrogate elephant mothers, simply because the endlings remain among us.
“If there is something the new baby white rhinos have to learn about social life or behavior, there is still a chance they can learn it from these two females. And they have a habitat where they could live, which I think is better than having a mammoth in the middle of nowhere,” he says. “The rhino habitat is ready. They could be poached there, but this is not an environmental constraint. It is a human constraint.”
But if the research is a direct result of human activity wiping out rhinos from the wild, the effort to save the white rhino is about how far we are willing to go in the other direction. It is about how far we will go to protect a species, to save the last of a kind, whose forebears are extinct because of us. And that is not a scientific constraint, but an entirely social one.
Rebecca Boyle is a science journalist in St. Louis. She is writing a book about humanity’s relationship with the moon. Justin Mott is an award-winning editorial, travel and commercial photographer and director based in Vietnam for over a decade. You can find more of his work on his website, Youtube, Twitter and Instagram. This article is part of a larger project titled Kindred Guardians.
This story is part of "The Future of Fertility" a new series on Discover exploring the frontiers of reproduction.