I was walking down a sandy trail perforated by volcanic rocks – the sharp, pointy kind that ruin boots and twist ankles. The heat was making my feet heavy and had scorched the trees to skeletons. While I walked and talked with other members of the group, thirsty mockingbirds hopped between the surrounding thickets.
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I was on San Cristóbal, the easternmost island of the Galápagos, an archipelago born from volcanoes. Here, evolution takes place at such speed that scientists observe certain islands day and night.
I was following in the footsteps of whalers and pirates, yet the animals here know no fear. Blue-footed boobies ignore you as they waggle their feet at prospective mates; spectacular marine iguanas glisten in the sun between swims.
My destination was a volcanic crater. Two craters now fused into one, its cool, muddy bowls are the perfect place for another Galápagos icon – the giant tortoise. Here, these creatures bathe, bask and, if they’re lucky, breed.
The group stopped for a drink, and a noise that was at once familiar and alien broke the silence: the mew of a kitten. Our heads turned in unison and our guide, Fernando, disappeared into the bush to investigate. In a place as highly conserved at this, we all knew what had to happen.
San Cristóbal was once overrun by cats, rats and goats. Some snuck onto the island with pirates and whalers in the 1600s; others were intentionally brought here by settlers in the 1700s. The herbivores outcompeted the leisurely tortoises for food and carnivores feasted on their eggs, and the population nosedived. Fernando radioed the location to a team who would take care of the matter, and we pressed on.
As a result of this vigilance, San Cristóbal’s tortoise population is on the road to recovery. The animals punctuate the sides of the trail, taking refuge from the midday sun under bushes. In the 1970s there were 600 individuals, mostly adults, a number thought to have since increased to 7,000. It’s a remarkable feat when you consider the pace tortoises like to keep – they take 30 years to reach sexual maturity. Galápagos hawks, mockingbirds and other species are also recovering on San Cristóbal, but other islands have not been so fortunate.
The decline of giant tortoises
South of San Cristóbal lies Floreana – one of the archipelago’s most southern islands. It was our original destination, but the threat of avian flu changed our plans. Its local wildlife is on the brink of collapse, with 54 species listed on the IUCN Red List as Endangered, Critically Endangered or Vulnerable, and a further 12 now locally extinct. The last wild Floreana giant tortoise to graze these volcanic hills died in the 1850s, not long after Darwin arrived on the Beagle.
Giant tortoises (14-15 subspecies have been identified across the archipelago, of which a dozen still survive) were considered a delicacy by generations of explorers and whalers. Even Darwin himself partook – naturalists of every period seemed compelled to eat each new creature they met. As pirate-cum-zoologist William Dampier wrote in the 17th century, tortoises were “extraordinarily large and fat, and so sweet that no pullet [a hen] eats more pleasantly”. In ships’ logs, tortoises have been likened to “buttery beef” and “unctuous mutton”, and even used as a digestive aid. In fact, after their discovery in the 1600s, it took nearly 300 years for a specimen to make it back to Europe without being eaten.
Floreana seemed to be the easiest place to grab a tortoise, and over the course of a hundred or so years, humans devastated populations here, before invasive species then gained a foothold.
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With Floreana’s wildlife in such bad shape, a radical approach has been needed. And that’s where the Restoring Floreana project comes in. Over the past two decades, volunteers, local residents and scientists have been working to take Floreana back in time. Their mission is to remove invasive species from the island whilst minimising the risks to the local community, native species and domestic animals, and restore the 12 species the island has lost, all of which, save the Floreana tortoise, survive elsewhere on the archipelago. It’s hoped their work will come to fruition in 2025.
How is the giant tortoise being brought back?
But how on Earth do you bring back a tortoise that’s been extinct for nearly 200 years? As it turns out, the sailor’s affinity for tortoise meat may well be the very thing that saves the reptiles.
In the north of the Galápagos, inside Wolf Volcano on the island of Isabela, there are tortoises that, to a biologist, have always looked a bit out of place. As Darwin famously observed, the two main types of giant tortoise shell – saddleback and domed – have evolved in response to food availability. In arid environments, the lofty ridge of a saddleback shell accommodates a long, flexible neck that helps a tortoise to access food in hard-to-reach places; in wetter climes, where food is abundant on the ground, domed shells dominate.
Scientists studying these tortoises in the 1990s noted that, despite the surrounding vegetation, their shells were more saddleback in shape, more akin to those of the tortoises on the drier islands of Pinta, Española and Floreana. In fact, as conservation geneticist Evelyn Jensen explained, these creatures seemed different from any tortoise on any island. “They are actually called ‘the alien tortoises’ in scientific papers,” she says.
To find a match for Isabela’s mystery tortoises, scientists analysed ancient museum specimens. They eventually discovered that the ‘aliens’ had considerable genetic similarity with the Floreana tortoise. The theory thus goes that, somewhere on the island, at least one Floreana tortoise survived and bred with the local population, producing baby hybrids (known as interspecific hybridisation, rather than species crossbreeding).
After that discovery, biologists were airdropped into Wolf Volcano in 2008 to take blood samples and implant microchips. In one day, they discovered more than 30 hybrids and, though this isn’t published work yet, Jensen shared that they’re finding all kind of hybrid tortoises across the islands, including some with Pinta DNA – the subspecies of which Lonesome George, who died in 2012, was thought to be the last.
So how did the Floreana tortoise cross the archipelago? “You can read it in ships’ logbooks,” says Jensen. “Sailors would load up on tortoises and then perhaps be chased by pirates - or perhaps they were the pirates doing the chasing. To speed up, they would dump tortoises overboard. The tortoises, we think, washed up on this northern point of the archipelago.”
In 2015, a team returned to Wolf Volcano, but only found one or two of the originally discovered hybrids. They switched to plan B, airlifting 30 tortoises that appeared to be of Floreana descent out of the crater. Of these, 20 or so would become breeding pairs, the starting point for the return of the Floreana subspecies.
But restoring extinct wild animals is rarely straightforward. “Scientific plans went to waste,” Jensen says, with a laugh. “We’d be configuring who should breed with who to ensure high genetic diversity, but one or two males seemed to be fathering all the young, and not all the females wanted to breed. Some tortoises would try to leave enclosures to be with different mates. Their personalities came out.”
So far, around 500 youngsters have been born to the project. When I ask how much ‘Floreana’ these hybrids are, Jensen corrects me. “That’s a misconception,” she says. “We’re not trying to recreate a pure Floreana subspecies, but a healthy population of new tortoises.” Creating a ‘purebred’ through husbandry would take centuries; Floreana doesn’t have that much time.
Not only is the giant tortoise emblematic of the Galápagos (Galápago is Spanish for tortoise), it’s also an ecosystem engineer. On islands like these, where the number of species is limited, there’s little by way of “ecological redundancy,” as Jensen puts it.
The whole plant community of the Galápagos is shaped by tortoises, who disperse seeds and act like bulldozers, keeping the woody vegetation from taking over. The environment will have changed since they died out, so if you want to restore Floreana, you need tortoises. Nothing else fills that ecological role.
“The hope is that, over time, natural selection takes over,” Jensen explains to me. “The individuals that do have Floreana ancestry may do better because they evolved there. Over time, the Floreana tortoise could return naturally. Or maybe not. At the very least, we hope the genetic variety that we put on the island gives natural selection the best chance.”
The restoration of Floreana Island
Floreana’s restoration is about more than returning an icon. It’s about giving the island a chance to restore its own balance. The project has been decades in the making, with giant tortoises only the final piece of the puzzle. Alongside geneticists, scientists such as Heinke Jäger from the Charles Darwin Research Station on Santa Cruz island have been investigating how best to restore the island’s plant species, without which there wouldn’t be much to eat.
Jäger’s work focusses on two species: Scalasia – a giant daisy tree that displays its own pattern of evolution across the islands – and the invasive blackberry. Scalasia isn’t just a tree, it’s an entire ecosystem, hosting insects that survive nowhere else. These invertebrates sustain birds such as finches and the vermilion flycatcher. On Santa Cruz, blackberry bushes take up valuable space that could otherwise be used by young native trees, and also disrupt birds’ hunting behaviour. “On Santa Cruz, the flycatcher also catches moths, so it needs an open area to hunt,” says Jäger. “Because of the blackberry, its feeding patterns are disturbed – and breeding pairs abandon their nests if they’re not catching enough food. As a consequence only around 25 birds are left on this island.”
Last year, the vermilion flycatcher only bred successfully in areas that Jäger’s team kept blackberry-free. Every year, these spaces produce five to seven chicks. These kinds of ecological lessons will be crucial if Floreana is to be a success.
Paula Castaño has been working on Floreana in stints since 2013 as a native species manager, and has been involved in the effort to rid the island of its invasive rodents.
“Things are looking promising,” she says. “When counting owls at night, we also used to see rodents – but that’s changed. Fruit is left on the ground. Land snails come out. Crabs and finches seem more common. Even the community is saying that now, rather than rodents eating crops, finches are eating the seeds when they’re planted.”
Restoring Floreana has always had the local community at its heart. These are the people who have powered the change, and for Castaño, putting Floreana’s people in control of its future has been the project’s highlight. “An elder told us how she used to see the vermilion flycatcher when she was young – it holds a special place in her heart,” she says. “I hope she will get to see this species back.”
It’s clear that Castaño is visibly excited to see the culmination of two decades of work, and I wonder how long it will be before the return of the so-called Floreana tortoise and the other 11 species.
“A month or two; no longer than a year,” she says. I ask how she’ll judge the success of the endeavour. “We’ve already been so successful in many aspects of learning. If a species doesn’t thrive, it doesn’t mean it was a failure. There will always be something to learn. There may be challenges, but every time I come back the place is stronger.”
Daniel Bennett is editor of BBC Science Focus. He visited the Galápagos courtesy of Hurtigruten, sailing on the MS Santa Cruz.
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