Resurrecting a Long-Lost Galapagos Giant Tortoise
If you go to Floreana Island, in the Galapagos, you can still see descendants of the giant tortoises that Darwin documented in the 19th century when he visited these islands. From the dock, just weave between indolent sea lions and impassive ruby-red marine iguanas and ask around for the truck to the highlands. It’ll be driven by one one of the locals and you can sit on a wooden bench in the back. Hop off at the Asilo de la Paz and wander around until you come across the largest land reptile you have ever seen, eating some iceberg lettuce on a concrete slab. If you’re lucky, he or she might cast an unimpressed look in your direction.
There are a handful of big tortoises up here in corrals, and some young, toaster-sized ones too. But these tortoises aren’t really the species that once lived on Floreana, Chelonoidis elephantopus. The last pure Floreana tortoise died out some time not long after Darwin visited in 1835, another tale of runaway human consumption dooming a species to extinction. The tortoises on Floreana today are mongrels from other islands, many bred from former pets. But it may be possible to resurrect the Floreana tortoise yet—by studying a long-lost population left by pirates on an extinct volcano.
Back before it was made illegal, many families on this island had a couple big tortoises ambling around as mascots. But all those ancient looking creatures originally came from other islands. One way you can tell is their shells—most of the post-pets have classically domed shells, while the original Floreana tortoises had a pronounced saddleback-shaped shell that allowed them to crane their necks up high and reach tall vegetation on this extra-dry and sparse island.
Geneticists knew from century-old museum specimens that Floreana tortoises had pronounced saddlebacks. A 1994 expedition found saddlebacks on remote Wolf Volcano on Isabela, more than 100 miles away.1 DNA tests of those specimens hinted that some might have genes from Floreana, so in 2008, a group of 50 researchers geared up and went looking for more tortoises with those saddle-shaped shells. They found all shapes and sizes of tortoises, and like proper scientists, took blood samples from 1,600 of them.
Back at the lab, this blood revealed many individuals that were hybrids of the Floreana species and another species. Their going theory is that whalers and buccaneers, who are known to have swung by the Galapagos to pick up some tortoise meals to go, may have stashed some Floreana tortoises near the remote volcano and then never returned to pick them up. The newcomers settled down and mated with the locals.
Although there were no pure Floreana tortoises, the researchers were excited to get their mitts on those genes. They were also excited to find some animals who seemed to be relatives of the late Lonesome George, the last of the Pinta Island tortoises—another saddlebacked species. For many conservationists, the ideal restoration of any island would involve not just reintroducing any old Galapagos tortoises, but introducing the right tortoises. They had to go back. With big nets.
“It was a huge task to actually find them and physically move them there,” says Luciano Beheregaray, a geneticist at Flinders University in Adelaide, Australia, and one of the scientists who went back to the Wolf Volcano in 2015 with GPS units, El Nino-level rain gear, and machetes. The team scoured the thick and spiny brush for animals with pronounced saddlebacks. “When we found a potentially important tortoise, we had to clear the area with machetes so the helicopter could drop the net,” Beheregaray says. This time, they used shell shape to identify promising candidates and airlifted 32 out.
Wednesday, in the journal Scientific Reports, a global team of researchers is reporting on the genes they managed to snag on that trip. No Pinta Island genes, alas. Lonesome George’s kind isn’t likely to plod the Earth again any time soon. But they got 23 tortoises (nine males and 14 females) with enough Floreana genes to start bringing that species back to life.
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These days, Crispr gene editing and cloning are being mooted as tools to bring back everything from the long-dead mammoth to the more-recently-extinct passenger pigeon. But in this case, no fancy genetic wizardry is required—you simply breed the tortoises with the highest levels of Floreana genes together until you have something with a very high percentage of those genes. It will take some time, though, since tortoises don’t reach sexual maturity for a quarter century.
The breeding process doesn’t have to be perfect for the tortoises to take hold: Once they are back in their native habitat, evolution will take over, says James Gibbs, a tortoise expert at the State University of New York College of Environmental Science and Forestry in Syracuse. “I am intrigued with letting these imperfect tortoises go and letting evolutionary process refit them to the island,” he says—adding that it is important to start with animals that at least have a saddleback, since they can reach more food during Floreana’s periodic and tough droughts.
However, if conservationists do succeed in bringing back Floreana, they’ll have some prep work to do. Today, the island is home to a thriving population of cats and rats that eat tortoise eggs and young—don’t be surprised if you see a rat or two flat on the road on the way back down the hill to the dock. If the renewed species is going to have a chance, these predators will have to go. Luckily, a conservation group called Island Conservation is planning just such an eradication in the next few years since the rodents also threaten rare birds like the Floreana mockingbird and the Galápagos Petrel.
Once the tortoises are back in large numbers, they are likely to change the face of the island. Where it is dense forest, they will uproot and knock down trees and bushes to make beds, creating a sort of tortoise savanna, says Gibbs. And they’ll move around the seeds of the cactus trees. Despite their modest pace, “they really are a major force,” Gibbs says.
The airlifted tortoises from Wolf Volcano, some likely over 100 years old, are settling in at a captive breeding center in Puerto Ayora, the Galapagos’s busiest city, on Santa Cruz Island. Just as they were once valued by pirates as containers of calories, they are now valued as containers of genes. But they are also individuals. “I can assure you that I helped to clean and prepare the corrals where they were housed and there is space, plenty of food and water,” says Beheregaray. “They are being treated there as Lonesome George used to be treated there—as special animals.”
1Update 4:30pm EDT 9/14/17: This story has been updated to correct the year of the Wolf Volcano expedition; its results were published in 2002, but the expedition occurred in 1994.
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