With wide three-toed hooves and no thumbs, Sudan could neither swipe right nor swipe left. But last April, he joined Tinder anyway, making him the only northern white rhino on the dating network. He was, indeed, the only male northern white rhino on the entire planet, and anyone who swiped right on his profile was asked to donate to research into artificially breeding rhinos. “I don’t mean to be too forward, but the fate of my species literally depends on me,” Sudan’s profile read.
On Monday, Sudan died at Kenya’s Ol Pejeta Conservancy. At the age of 45, Sudan was an elderly rhino who suffered from various age-related problems and infections. After his health took a dramatic downturn, a team of vets made the decision to euthanize him. His death means that the total northern white rhino population on Earth stands at just two: Sudan’s daughter, Najin, and his granddaughter, Fatu. Neither was born in the wild.
Sudan’s death is certainly a tragedy—the heartbreaking end of a momentous individual life, and a moment of symbolic import for the world. But it doesn’t really change the fate of the northern white rhino, which was already functionally extinct long before Sudan died. After all, both Najin and Fatu are highly inbred, and neither of them are capable of reproducing naturally. The only way to save the northern white is to now artificially inseminate their eggs with stored sperm from Sudan and other males, and implant the resulting eggs into females of the closely related southern white rhino.
In the 1960s, an estimated 2,300 northern white rhinos still lived in the wild. But in the following decades, pseudoscientific beliefs about the medical properties of rhino horn created a lethal demand that poachers rushed to fill. By the early 1990s, there were just a few dozen left. In 2008, the creature was believed to be extinct in the wild.
Sudan escaped the fate of his wild peers. In 1975, he was captured by animal trappers at the age of 2, and moved to Dvůr Králové Zoo in the Czech Republic. In 2009, he and three others—Najin, Fatu, and an unrelated male, Suni—were moved to the Ol Pejeta Conservancy to take part in a last-ditch breeding program. It didn’t work. Even when rhinos mated, none of the females achieved a confirmed pregnancy. In 2014, Suni died. Now, Sudan has joined him.
It’s important to note that the white rhino is not extinct. The northern white is one of two subspecies that are separated by around a million years of evolution. And the other subspecies—the southern white—is something of a success story.
At the end of the 19th century, it was down to just a few dozen southern white rhinos, clinging to existence in a single South African reserve. Now, there are more than 20,000 of them in the wild—more than any other rhino subspecies. Still, that incredible comeback is precarious. Most of the southern whites live on private lands in South Africa, but as their numbers have grown, their value has fallen. An increasing number of landowners are “seeking to get rid of their rhino,” according to the International Union for Conservation of Nature. This, combined with the ongoing threat of poachers, threatens to reverse the successes of the last century.
In 2010, three researchers argued that the northern and southern white rhinos are physically and genetically distinct enough to justify classifying them as two distinct species. But defining a species is controversial. There are dozens of ways of doing so, and working out whether two groups are subspecies or species can be like working out whether a mound of sand qualifies as a pile or a heap. In the case of the northern and southern white rhinos, the conservation community still largely counts them as subspecies.
In many ways, this is an academic debate with little real-world import. Classifying something as its own species can influence how you might go about protecting or breeding an animal, but the northern white rhino is already too far gone. Even when there were still four living individuals, conservationists argued that the survivors were so inbred and genetically narrow that they couldn’t give rise to their own viable population. The only way to preserve some northern white-rhino genes is to artificially interbreed them with southern whites.
That work is now underway—but it’s tricky. A rhino’s ovaries lie two meters within its body, so collecting eggs requires shoulder-length gloves and a lot of dexterity. Scientists have perfected the technique on southern-white females, and they’re now ready to try on Najin and Fatu, whose eggs could then be fertilized in a laboratory. Another possible approach involves taking frozen cells from Sudan and other northern whites, transforming them into stem cells, and nudging those into becoming sperm and eggs.
In both scenarios, the resulting embryos would then have to be implanted back into a surrogate mother—something that hasn’t been done before. And even if all of that works, the Ol Pejeta Conservancy estimates that it would cost as much as $9 million to create a viable breeding herd of northern whites. “Yet this is the hope for preserving an entire subspecies,” they wrote.
These techniques might also help to save other species of rhino that are teetering on the edge. There are fewer than 100 Sumatran rhinos left in the wild, and around 60 Javanese rhinos. The Indian rhino and black rhino are doing better, but even their populations stand at around 3,500 and 5,000 individuals, respectively.
“I am hoping that Sudan’s death won’t be in vain, that it will mean something and that it will prompt people to take action,” wrote Elodie Sampere, a communications manager at Ol Pejeta, in a Facebook post. “For now, I will spend the day remembering my old friend and hoping he is in rhino heaven enjoying amazing rainstorms and lots of carrots.”