Resurrecting the lost giants of the Galapagos

National Geographic

a day ago

They enthralled sailors. They inspired Darwin. Then, by the mid 19th-century, the iconic Floreana tortoise was gone. Here's how a group of persistent scientists unlocked the secrets to bringing them back. The Galápagos Islands were named for the giant tortoises that have inhabited the archipelago for millions of years. Animals with mixed lineages like this one populate a remote corner of Isabela Island, which has emerged as a hotbed for genetic research. Photographs and video by Lucas Bustamante
In October 1820, the Nantucket whaling ship Essex laid anchor at a blue-green harbor on the Galápagos island of Floreana, more than 600 miles off the coast of Ecuador. The sailors rowed their whaleboats ashore and followed paths trampled by ancient reptiles, through broken basalt and tangled thickets of saltbush and cactus—'keeping a sharp look out,' wrote cabin boy Thomas Nickerson, 'for the object of their search.'
They were hunting for Galápagos giant tortoises. The animals varied from island to island—some had round, domed carapaces while others had shells that curved up at the front like Spanish riding saddles—but all could provide food for multiple sailors. When the whalers found a small 'turpin,' they'd flip it over, tie canvas straps to each of the creature's legs, then hoist the tortoise onto their backs like a knapsack. They'd tie the largest ones, some weighing more than 500 pounds, by their legs to long poles, hauling them two or three men per side across sharp and uneven lava rock and back to their ship.
There, they'd stack their captives upside down in the hold like nesting bowls. Tortoises could live up to a year without sustenance. 'They neither eat nor drink, nor is the least pains taken with them,' wrote Owen Chase, the ship's first mate. 'They are strewed over the deck, thrown under foot, or packed away in the hold, as it suits convenience.' The Essex took more than 60 of Floreana's tortoises, which had the curved shells known as saddlebacks and were, Nickerson wrote, 'the most rich flavourd and delicious meat I have ever met with.' Then the ship set off for the Pacific whaling grounds, where, a month later, it was rammed by a whale, a disaster that provided the inspiration for Herman Melville's Moby-Dick. The sailors salvaged as many tortoises from the foundering ship as they could fit on their small whaleboats, eating them—and eventually, each other—on their ill-fated voyage back to the South American mainland. The other tortoises sank with the ship or floated away. A hybrid Floreana tortoise walks along the foothills of Wolf Volcano in North Isabela Island
The Essex was far from alone in its plundering of Galápagos tortoises. When Charles Darwin arrived at Floreana in 1835 on the journey that would spark his theory of evolution, he heard of whaling vessels taking as many as 700 tortoises on one visit. 'Their numbers have of course been greatly reduced in this island,' he wrote. Historians estimate that between 1774 and 1860, passing ships took some 100,000 of the nearly 300,000 tortoises that lived on the islands when the Spanish arrived in 1535, driving populations of all 15 Galápagos tortoise species into steep decline and three to extinction. The Floreana tortoise, last seen in the 1850s, was the first to disappear.
Almost two centuries later, though, the Floreana tortoise is set to become the first extinct Galápagos species to be returned to its ancestral home. The revival of these gigantic creatures arrives at a moment when the 'resurrection' of dire wolves is making headlines and scientists are working to retrieve the genes of other long-gone creatures like woolly mammoths. But such prehistoric species would return to a world that has lived without them for millennia. The descendants of the Floreana tortoises, by contrast, will be reintroduced to the place where they once belonged, playing a critical role in an ecosystem that still desperately needs them. To accomplish that, a team of dedicated scientists has not only pushed the frontiers of genetic sequencing to identify a species that had been hidden from plain view, but also traveled to remote corners of the archipelago and sorted through bones and shells from dusty archives to right one of the great wrongs of Galápagos history.
This improbable scientific journey began in 2000. As a team of conservation scientists traipsed through the densely vegetated gullies at the base of the secluded Wolf Volcano on the northwest island of Isabela, they confirmed earlier observations that some of the tortoises there looked different. The animals had saddleback shells, a sign that they were a separate species from the more familiar domed ones on the volcano's higher, wetter slopes. 'There were pockets of tortoises that looked out of place,' remembers conservation biologist James Gibbs, a National Geographic Explorer and leader of the Galápagos Conservancy, which works to protect and restore the archipelago's wild ecosystems.
(How new initiatives are protecting the Galápagos for future generations.) The large, sturdy feet of a Galápagos tortoise help to support its immense weight. When the Spanish arrived in 1535, hundreds of thousands of tortoises lived on the islands. In the following centuries, the animals' flesh became a staple for hungry sailors, threatening the species' survival. But for the past 50 years, tortoise populations have begun to rebound under the protection of Galápagos National Park officials, scientists, and conservation groups.
To learn more, Gibbs and the team took blood samples 'from every unusual-looking tortoise' they encountered, placing identification tags on as many as they could, and sent the specimens to their research partner Adalgisa 'Gisella' Caccone, an evolutionary biologist at Yale University and a National Geographic Explorer. When she analyzed their DNA, she couldn't identify their genetic sequences. They didn't match those of any living tortoise species in her genetic database. Caccone was bewildered. 'I called them 'aliens,' ' she says. 'We didn't know where they came from.'
The researchers considered the possibility that some of those aliens could have floated ashore from whaling ships like the Essex. Banks Bay, on the volcano's western flank, was the final Galápagos anchorage for many ships on their way to the whaling grounds, and sailors were known to sometimes throw their surplus overboard before setting sail. Some of those unwanted animals may have floated to shore and ascended the volcano's ragged flank, living among the native tortoises and eventually breeding with them.
The whalers were responsible for the loss of so many tortoises—killing and eating most and carrying a number back home as trophies or pets. But perhaps, the scientists speculated, they had also inadvertently ensured the survival of the animals' genes. Only after several advances in genetic sequencing technology would the group realize the sailors had provided important clues to revive a species.
Scientists have been working to save the giant tortoises of the Galápagos since the middle of the 20th century, when only a few thousand were left on the entire archipelago. The whalers were gone, but tortoises had continued to fall prey to the creatures they brought with them—rats, pigs, dogs, and ants that fed on eggs and hatchlings, and goats and donkeys that disrupted and devoured their food supply. Galápagos National Park officials knew they had to do something or risk losing entire species. Beginning in the 1960s, conservation teams used the limited tools then available to save them.
(How fellow Galápagos residents learned to embrace the heat.)
They started on Española Island, east of Floreana, where the population had been reduced to 14 individuals. Between 1964 and 1974, park officials moved all the tortoises from the island to the Charles Darwin Research Station at the park's headquarters on Santa Cruz Island. With the help of a strapping male brought in from the San Diego Zoo that, according to records, had come from Española in the 1930s, they bred thousands of young. After a laborious campaign to eradicate goats from the island, they then reintroduced the hatchlings, and today more than 3,000 tortoises live there.
Park teams replicated that success on other islands as well. But despite those triumphs, there was one glaring disappointment: not finding a mate for the very last tortoise on Pinta Island, north of Floreana. Scientists had rescued the animal they named Lonesome George from his native island in the early 1970s, transporting him to a corral at the park's research station in hopes of preventing a fourth species from going extinct. In the years that followed, they anxiously searched for a partner. They first scoured Pinta with no luck. Then they placed females of other species with saddleback shells that resembled those of the Pinta in George's corral at the research center. When he showed no interest in breeding, they tried artificial insemination; the females did, finally, nest in George's corral, but the eggs were all infertile. By the early 2000s, the conservation icon was close to 100 years old, and time was running out for the species. Close up of a hybrid tortoise on Wolf Volcano
At the same time, developments in genome sequencing were allowing Caccone to expand her tool kit to identify the Wolf Volcano aliens. In 2006, she used a new method of DNA analysis to retest the samples. She made the astonishing discovery that the scientists had collected blood from a tortoise whose genes appeared to be 50 percent Pinta. Perhaps it wasn't too late for Lonesome George, and they could find Pinta relatives on the island and save the species. Thrilled, she proposed that the park send another expedition to the volcano. 'We said, We have to go back there. We need to find this animal. If there is one, there could be many more.'
Still trying to pinpoint the other strange Wolf Volcano genes, she also began to look more closely at the three species then believed to have gone extinct: the Santa Fe tortoise, the Fernandina tortoise, and the Floreana tortoise. Without the DNA of live animals to compare to the alien genes, the only cells available for sequencing were from old specimens carried across the ocean by whalers or scientific collectors. 'We went around to museums to collect samples of bone and skin,' Caccone says. At the American Museum of Natural History, they found bones a New York naturalist had unearthed in 1928 from lava caverns on Floreana, deep chasms where some tortoises had tumbled and died; at Harvard University's Museum of Comparative Zoology, they found bones and shells collected in 1834 and 1872. 'They were very porous,' she says, 'gray-looking,' crumbly, and desiccated.
Even so, she managed to scrape enough genetic material to obtain sequences of their DNA. And 'Boom!' she says. The alien tortoises 'were in the same clade'—ancestral grouping—'with Floreana.' The saddlebacks were hybrids of the native Wolf Volcano domed species mixed with the long-extinct Floreana saddleback species. The scientists' speculations had been correct. The whalers' castaway tortoises had survived and interbred. Preserved bones and shells of extinct species have been crucial to the work of evolutionary biologist Adalgisa Caccone (right). She and her team relied on artifacts that had, like this shell (left), been found on Floreana Island in 1928 to determine that a number of mystery tortoises on Isabela were descendants of the long-extinct Floreana species.
In 2008, a large expedition returned to Wolf Volcano to collect more samples so the team could get a better idea of how many Floreana and Pinta tortoises were on the island and search for possible mates for George. Teams from the park and the Galápagos Conservancy set up camps around Wolf Volcano and collected blood samples from 1,667 tortoises, placing identification tags on each one. In her Yale lab, Caccone analyzed those samples against her expanded database and found 17 tortoises with Pinta genes—and 84 with Floreana ancestry.
Still hoping to find more Pintas, the park team embarked on the lengthy process of planning, permitting, and funding another expedition to the volcano with a helicopter and nets to allow them to retrieve those hybrids. But in June 2012, Lonesome George's keeper found him dead in his corral. End of his line, end of his species. (Later, a necropsy would reveal George had an anatomical problem with his sperm duct and was probably incapable of reproducing.)
As scientists relinquished the idea of saving the Pinta species, they focused on the Floreana hybrids. 'People had given up hope so long ago' for the species, explains Gibbs, that it took some time for the researchers to understand the opportunity that these numerous living relics presented. But when they did, they realized, 'Wow, this is actually as significant' as finding Pinta tortoises on Wolf Volcano, says Gibbs. It was then that the conservation team began to consider a radical proposal: capturing and breeding the descendants of the species and repopulating Floreana, where the animals hadn't lived for more than 150 years.
Returning tortoises to Floreana wasn't important solely because scientists had found a lost species; it was also ecologically critical. Here in the Galápagos, Darwin had observed that species were exquisitely adapted to their habitat. Only recently have ecologists begun to realize how exquisitely adapted habitats are to the creatures that live there.
When the last tortoise disappeared from Floreana, the island's species suffered. Important native plants began to die off, while populations of invasive pests, plants, and livestock exploded, eating or outcompeting native plants and animals. By the end of the 19th century, the island's mockingbirds, racer snakes, rails, and hawks had disappeared. In the years that followed, finches, barn owls, lava gulls, and vermilion flycatchers went missing too.
Park officials hope to mend the hole in the ecosystem the lost tortoises had left behind. 'Without giant herbivores, the balance of an island ecosystem can collapse,' says Washington 'Wacho' Tapia, a biologist who has worked in Galápagos conservation since the 1990s. Tortoises are 'ecosystem engineers,' shaping vegetation as they move like bulldozers across the landscape. 'They flatten the ground and open the land for small reptiles, ground-nesting seabirds, and native plants,' says Tapia, keeping weeds at bay, helping native cacti regenerate, spreading seeds with their dung, and creating ponds and wallows that also harbor other species. A few decades ago, scientists visiting Wolf Volcano encountered tortoises with long necks and curved shells, shown here. The animals appeared unlike those that were native to the area, a realization that sent the team on a quest to determine where they came from.
Researchers knew that the animals had helped restore ecological balance on other islands. On Española, for example, scientists observed native grasses and cacti recovering, along with the lava lizards and albatross that had declined in the tortoises' absence. Where the giant reptiles have returned, ecosystems have flourished. 'This is a bit of a change of mind in restoration,' notes Arturo Izurieta Valery, who until recently was the park's director. Today conservation teams bring back missing animals with a focus on 'an extended ecosystem restoration.'
Scientists' new knowledge of species genetics allows them to make certain they are breeding creatures that are truly suited to surviving there. 'The goal of all of this work has never been to do de-extinction or re-create the Floreana tortoise,' says University of Newcastle conservation biologist Evelyn Jensen, a former postdoc of Caccone's, 'because that's never been possible.' Tortoises live too long and take too much time to reproduce, and achieving something close to purity, she says, 'would be a 500-year project.' The goal, instead, is for the descendants of the extinct species to return, survive, and fulfill their ancestors' ecological role in their native habitat.
But Floreana had changed dramatically since a native tortoise last roamed the island. Now there's a community of 150 people there, along with their pets and livestock—and thousands of rats and feral cats that, if left alone, would eat eggs and hatchlings and compromise the species' ability to reproduce. Soon after setting their sights on the Floreana species, park officials began meeting with the island's residents to secure their approval for a plan to poison and trap the rats and cats. These invasive animals would need to be eradicated or strenuously suppressed to ensure tortoises could once again populate the island. On Santa Fe Island, where native tortoises are extinct, park rangers have released a similar species that they bred in captivity and then flew to the island via helicopter.
As those negotiations moved forward, the park finally put preparations in place to send an expedition to retrieve the hybrids from the volcano. In 2015, the scientists arrived just before the wet season, spreading out across the volcano, using machetes to push through the thick underbrush. 'You don't have shade, water,' says Tapia. 'There are ticks all over your body.' It was a grueling landscape, which made the survival of these transplanted creatures all the more remarkable. When the rainfall began, the encañadas, ravines that flood during storms, began to flow. 'We could hear tortoises crawling from all over to the waters,' he says. Researchers gathered two or three at a time; then, as the helicopter hovered overhead, they loaded them into a large net and dropped them onto cushioned beds of car tires on the ship's deck, stacking them belly-up in the hull much as the whalers had two centuries earlier. 'It looked like a Noah's ark for tortoises,' Caccone says. 'At the end, the hull was full, and we'd put them everywhere on the sides.'
The team found 'thousands and thousands' of tortoises on the secluded volcano, Caccone says, and collected 30 Floreana hybrids. But they couldn't bring them to Floreana yet. Instead, they would have to transport the animals to the national park's breeding center on Santa Cruz Island, in hopes of building a healthy population.
Caccone's scientific insights continued to guide the team after the expedition. Once the adults arrived at the research station, she analyzed their genes to create a 'stud book,' a list of the individuals with high proportions of Floreana genes. The objective was to match up the hybrids to both increase Floreana genes in their offspring and protect their genetic diversity. 'If we release all identical individuals and a virus comes by,' she says, 'they could be wiped out.'
When it came time to mate them, the breeding team placed three hembras—females—with two machos. Any more, and the males would get into fights. The tennis-ball-size eggs produced from those couplings—up to 15 per clutch—hatched in incubators. The hatchlings, each about the size of the palm of your hand, then moved to age-sorted corrals to mature until they were big enough to survive reintroduction, at around five years old. All of the Wolf tortoises' offspring have proved to be 'incredibly fit and robust,' says Gibbs. Today 600 Floreana hybrids live in the breeding center, and 300 are old enough for reintroduction. The archipelago's captive-breeding programs call for careful monitoring of the hatchlings that scientists shelter and feed (left). Volunteer Erika Kubisch and conservationist Walter Chimborazo (right) transfer tortoise eggs from their nests to incubators in the breeding center on Santa Cruz Island.
Down a sandy path in the far reaches of the research station, park breeding director Freddy Villalba throws an armful of branches of porotillo, an introduced tree with large, shield-shaped leaves, into a shady corral that contains 141 of the oldest and biggest Floreana hatchlings, each now nearly two feet long and ready to return to the island. They converge on their food, extending their long necks and hissing as they jockey for position, climbing over each other like monster trucks to get to the branches and soon reducing their breakfast to gray, desiccated sticks. Villalba calls this enclosure the corral de las locas—home of the crazies.
Caccone knows more about these young tortoises than was conceivable even a decade ago. She has now sequenced multiple genomes of all the living Galápagos tortoise species using nuclear DNA, the individual genetic manual 'that makes you who you are,' as her colleague Evelyn Jensen explains. That in-depth nuclear-genome analysis has provided some additional surprises. Caccone's early work had shown that the Wolf Volcano aliens had a mix of Floreana, Isabela, and Pinta ancestry. But after examining more museum specimens, Caccone and Jensen realized that the Wolf hybrids had less Pinta ancestry than they originally thought. Instead, the team found genes from Española tortoises. 'It's not just two species hybridizing; it can be three or maybe even four,' says Jensen. This is a good thing, the scientists believe. With 'complex ancestry,' she adds, 'they're actually quite genetically diverse.'
What will happen next remains a scientific mystery. Perhaps the hybrids with the most native genes will flourish on Floreana. But the island is a different place now, a 'novel ecosystem,' as the ecologists say, where native organisms mix with human-introduced ones. The locas will have to contend with thickets of invasive blackberry shrubs and lemon and guava trees brought by early human settlers, with scarcer stands of the cactus they love to eat and a changing climate. Ecosystems don't stand still; neither do species or their genes. The team will put the tortoises on the island, says Caccone, then let natural selection take its course. 'Whatever survives will probably be best suited to live on the island,' she says. 'Whatever survives will have some genes from Floreana.' At the Santa Cruz breeding center, tortoises like this one are being bred for reintroduction on Floreana Island, where they went extinct years ago. Today about 300 of these so-called Floreana hybrids are ready to be released, after a long campaign to clear the island of non-native rats and feral cats that could prey on the fragile young tortoises.
To help the newcomers, the park and a local conservation group have, over the past several years, prepared a number of measures to wipe out the invasive cats and rats that pose a risk to tortoises. At the end of 2023, as the culmination of that effort, two ultralight helicopters lifted above Floreana and scattered many thousands of blue, kibble-size pellets of rat poison over areas unpopulated by people, while teams spread pellets by hand near homes and farms and set out traps and poisoned sausages to kill the cats. Park officials had planned to put the first tortoises on the island the following December, when the onset of the rainy season would ensure more food for the young reptiles. But camera traps found that 40 or 50 rats had survived the poison, and they postponed the reintroductions. They now plan to release the tortoises when the rains begin to fall later this year.
Even without full eradication, however, the ecosystem has begun to rebound. With fewer cats and rats, Floreana cuckoos, mockingbirds, and doves have come back. Earlier this year, park workers heard the song of a Galápagos rail, a bird last seen on the island in 1835—a musical chi-chic-chi-chirroo not heard since the days of the whalers.
When the locas finally go home, they'll travel by ship to a wharf in the small village of Puerto Velasco Ibarra, then in trucks to the east side of the island. As they approach the highlands, park rangers will complete the journey by strapping the animals, weighing up to 30 pounds, onto their backs, much the same way those whalers carried away their forebears. Life on the island will be hard for the hatchlings, accustomed as they are to their cushy corrals, in this stark and unforgiving landscape: the harsh sun, the contorted lava, the scorching black soil, the perilous wet-season torrents, and the extended spells of drought. This place is not so much a cradle of life as a testament to life's difficulty and urgency—and its drive to continue.
'What a trifling difference must often determine which shall survive, and which perish!' Darwin wrote. These hybrid creatures will survive, or perish, in a hybrid world.
(To see iconic Galápagos wildlife, visit this island instead.) This story appears in the September 2025 issue of National Geographic magazine.
The nonprofit National Geographic Society, committed to illuminating and protecting the wonder of our world, funded the work of National Geographic Explorers Hannah Nordhaus and Adalgisa Caccone. Learn more about the Society's support of Explorers. Support for photographer Lucas Bustamante's work on this story was provided by Focused on Nature and Savia Fund.
A Colorado-based writer and Explorer since 2019, Hannah Nordhaus journeyed to the Galápagos Islands to report on a remarkable effort to return a lost tortoise species to its ancestral home. Her stories have also appeared in Wired, Ski, Outside, and other publications.
On his first assignment for the magazine, Galápagos-based Lucas Bustamante visited six islands. A biologist, he is the co-author of three books on Ecuador's biodiversity. Tropical rainforests and islands, he says, are his favorite 'offices.'