Score one for the giant tortoise: The descendants of one thought-to-be extinct species have apparently been chilling on the side of a volcano, eating grass for the last few hundred years. Scientists say breeding these animals could bring the species back from the brink. A report on the tortoise surprise was published on the preprint server bioRxiv.

Once upon a time, the Galapagos archipelago was a veritable paradise for 15 different species of giant tortoise. Then, humans showed up and the lumbering slowpokes began to disappear with alarming speed. Three centuries of human depredation wiped out 90 percent of the islands’ tortoises. Four entire species, including Floreana (Chelonoidis elephantopus) and Pinta (C. abingdoni) tortoises, completely disappeared. Or so we thought.

Then in 2008, DNA tests revealed that 105 of the tortoises living on Floreana Island had some C. elephantopus blood in their veins, mingled with ancestry from another species on the island. None of the tortoises were purebred, but scientists’ curiosity was piqued.

Seven years later, a team of 70 field researchers set out to see if they could find more. And there, on the grassy side of a volcano, they did: 144 tortoises with C. elephantopus’s distinctive saddle-shaped shell.

Blood tests from the volcano dwellers and six tortoises already in the islands’ captive breeding program revealed a rich field of Floreana tortoise DNA. Most of the samples included some of the thought-extinct species’ DNA, and two individuals appeared to be 100 percent, uncut C. elephantopus.

The researchers collected 23 of the tortoises, including the two apparent purebreds, and added them to the captive breeding program—after checking to make sure none of them were related. A few generations of baby tortoises would be enough to bring the species back.

Craig Stanford is a tortoise and turtle expert at the International Union for Conservation of Nature. He was not involved with the research but expressed excitement about the possibility of bringing Floreana tortoises back.

“We have the opportunity to restore a critically rare and biologically remarkable species to its natural habitat, which is an amazing chance that doesn’t come along very often,” he told New Scientist. “I’m cautiously optimistic about the odds of success.”

The paper’s authors note that the rogue population on the volcano’s slopes may be the result of the same human interference that obliterated the rest of the species. “Ironically, it was the haphazard translocations by mariners killing tortoises for food centuries ago that created the unique opportunity to revive this ‘lost’ species today.”

[h/t New Scientist]