Genetic breakthrough rebuilds Galápagos tortoise populations

Photo by: Luca Ambrosi on Unsplash

Since Charles Darwin’s Origin of the Species, the giant tortoises of Ecuador’s Galápagos Islands have been synonymous with scientific discovery and the evolution of life on earth. Now they are returning to the spotlight, as a cutting-edge project revives extinct species using the genetic fingerprints that live on in their descendants. 

Of the more than 200,000 giant tortoises that once roamed the Galápagos, only 10 per cent remain. Overexploitation by whalers and pirates in centuries past, followed by predation and habitat destruction by invasive species, decimated their numbers. On some islands they’re now extinct: Floreana and Santa Fe islands lost their tortoises in the mid-1800s; and by 2012, Pinta Island joined them with the death of Lonesome George, a male Pinta Island tortoise and the last known individual of the subspecies, which, in his last years, was known as the rarest creature in the world. 

There is hope, however, in the form of a ‘happy accident’ of genetic discovery. Decades of genetic analysis of Galápagos tortoises – both from the wild and from museum specimens – have revealed that the extinct Floreana tortoise lives on in hybrid individuals on Isabela Island. It is thought that these hybrids came about after whalers abandoned a mixture of tortoises there, over a century ago. 

Iniciativa Galápagos – a collaboration between the Galápagos National Park Directorate and Galápagos Conservancy – has been working to repopulate the islands’ giant tortoises for 20 years. Scientists from Yale University’s Center for Genetic Analyses of Biodiversity and at Newcastle University in the UK are collaborating with the initiative to understand both the tortoises’ evolutionary history and the role of genetics in their repopulation. 

The project shipped groups of adult tortoises from Isabela Island to its breeding centre on Santa Cruz island where the Yale and Newcastle geneticists made their discovery that many of the tortoises had a high percentage of Floreana genome (a genome is a complete set of DNA). They established a modern-day Noah’s ark to resurrect the Floreana tortoise, but for it to truly succeed, ongoing genetic screening is necessary to organise the best mating pairs and monitor their offspring. 

So far, the breeding programme’s genetic analysis of hybrid tortoises could only give a limited view of the extinct species DNA they carry. Now scientists are developing a game-changing tool that will give a much broader picture, showing the quantity and quality of Floreana DNA in each tortoise. This will ensure the breeding programme selects tortoises with the highest conservation value. 

“Using hybrid species to repopulate islands in this way is unique,” says Dr Jorge Carrión, director of conservation at Galápagos Conservancy. “We hope the work of everyone involved will inspire both conservationists and the public, demonstrating that dramatic population restorations are possible.” 

Soon, tortoises will return to Floreana Island for the first time since the mid-1800s, just a decade or two after Darwin’s first visit. The release of a healthy tortoise population, genetically close to the original species, will drive a broader ecological restoration of Floreana. Other native species no longer present on the island – such as mockingbirds and snakes – will also return. 

The Galapagos National Park Directorate partners with the Galápagos Conservancy to carry out research and conservation, breeding and rearing tortoises from threatened species, repopulation of islands where tortoises went extinct, and managing conflicts between tortoises and humans. Galápagos Conservancy is a US not-for-profit organisation focused exclusively on protecting the unique biodiversity of these islands. Its approach is to build strong working relationships with scientists and the full Galápagos community.  

Oak supports Galápagos Conservancy in its work to repopulate islands where giant tortoises have gone extinct. This is part of our Special Interest Programme, which provides the space and flexibility to make grants outside of Oak’s other programme strategies. Grants support partners in a wide range of fields including medical research, education, environment, humanitarian relief, mental health, the arts, and much more.