Because of this history, Novak says scientists waited to announce this latest horse’s birth until he survived infancy. Even now, they’ll have to monitor his health for the rest of his life. As for Kurt, he’s in “great health,” Novak says. He now lives at the San Diego Zoo Safari Park with a female Przewalski’s horse, Holly.

Even if the two clones remain healthy, they won’t be released into the wild—but their children or grandchildren will. Novak says they will become breeding stallions when they reach maturity at age 3 or 4. “Their purpose in life is to breed as much as possible, so we want them to live as long as possible,” he says. The team also plans to continue cloning more Przewalski’s horses.

Not every endangered species is suitable for cloning. The technology relies on having cell samples from animals, which aren’t always easy to obtain. (And to take it a step further, the lack of a complete genome is one of the reasons why efforts aimed at the “de-extinction” of long-ago animals like the woolly mammoth aren’t using cloning, but are instead aiming to edit the DNA of a related species, like the Asian elephant, to create a hybrid.)

Plus, a domestic species often needs to serve as a surrogate—this ameliorates the risks of taking an endangered species out of its natural habitat and putting it through the surrogacy procedure. But for many endangered species, there are no domestic animals that are genetically similar enough to carry a successful pregnancy.

David Jachowski, associate professor of wildlife ecology at Clemson University, says cloning alone won’t save endangered species. “As a scientist, it’s intriguing. We’re going from science fiction to reality,” he says. “But the reality is, if we don’t address the threat the species faces in the wild, making more of them to release in the wild isn’t going to move the needle on their recovery.”

The real problems that threaten most species, he says, are environmental, and cloning can’t fix those. Jachowski previously worked at the US Fish and Wildlife Service, where he helped coordinate the recovery of the black-footed ferret, an endangered North American animal. The species was close to extinction after its main food source—prairie dogs—were decimated by disease, habitat loss, and poisoning campaigns.

In 2020, the same team behind the horse clones collaborated with the agency to clone a black-footed ferret named Elizabeth Ann. But so far, that effort has only produced a single animal, and she has not reproduced. The Fish and Wildlife Service’s broader efforts have focused on more conventional conservation techniques, like restoring prairie dog populations while releasing captive-born black-footed ferrets into the wild.

Noah Greenwald, endangered species director at the nonprofit Center for Biological Diversity, doesn’t think cloning will be a major part of endangered species recovery because of its limitations. He thinks more traditional strategies, like addressing habitat loss and competition from invasive species, will remain the most effective tactics. He sees it as a last-ditch effort: “For the species that really are down to such a small number of individuals, it’s a possible way to increase the gene pool,” he says.

For the Przewalski’s horse, at least, cloning offers hope for future survival of the species. The team that created the new foal didn’t say what kind of animal they’ll clone next, but there are plenty of options. The San Diego Zoo’s frozen repository contains cell lines from more than 1,100 species and subspecies—some of them critically endangered. Russell is looking forward to the next conservation project. “Hopefully they have more animals in their bank that they allow us to produce in the future,” he says.

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