For more than a century, scientists believed one of the Galápagos Islands had lost its giant tortoises forever. Then, high on a remote volcanic landscape on another island, researchers encountered animals whose unusual shells raised a question that seemed almost impossible: could a tortoise thought extinct 150 years ago still have descendants alive somewhere in the archipelago?
The discovery came in 2000 during an expedition to Wolf Volcano on Isabela Island, the highest point in the Galápagos. Researchers noticed giant tortoises whose distinctive, saddle-shaped shells did not fit neatly with the population they expected to find there. Unsure of what they had encountered, they began referring to them as “aliens,” according to James Gibbs, a conservation scientist who was involved in the research and later work on the population, in an account published by CNN.
The mystery became more extraordinary when genetic analysis revealed that some of these tortoises carried ancestry from the Floreana giant tortoise, a lineage believed to have disappeared from Floreana Island around 1850.
A tortoise shaped by millions of years of isolation
The history of these animals begins millions of years before humans reached the Galápagos. Giant tortoises are believed to have arrived in the archipelago from mainland South America roughly 2 million to 3 million years ago. Once isolated on different islands, populations evolved independently, developing distinct physical characteristics.
That island-by-island variation later became part of the natural history that fascinated Charles Darwin when he visited the Galápagos in 1835 aboard HMS Beagle . Observations of differences between island populations helped shape the ideas that became central to his theory of evolution.
But the same isolation that produced such remarkable diversity could not shield the tortoises from humans.
Their greatest survival skill became a weakness
From the 16th century onward, pirates and whalers began visiting the Galápagos. Giant tortoises offered something sailors desperately needed during long voyages: a source of fresh meat that could be kept alive for over a year without regular supplies of food or water.
The animals' ability to survive for exceptionally long periods made them unusually convenient cargo. CNN reported that sailors could keep tortoises aboard ships and slaughter them when needed.
That exploitation had devastating consequences. An estimated 100,000 to 200,000 giant tortoises disappeared from the Galápagos over about two centuries, according to figures cited by CNN. Several island populations were driven to extinction.
Floreana's tortoise was among the earliest casualties. By around 1850, the island's giant tortoise was considered extinct. For the next 150 years, there was no confirmed population living on Floreana.
The ‘aliens’ changed the story
The Wolf Volcano discovery offered the first major clue that the Floreana lineage had not completely disappeared. Genetic testing showed that some of the unusual tortoises had Floreana ancestry. Later genetic work found some young Wolf Volcano tortoises with roughly 50% Floreana ancestry and 50% native Wolf Volcano ancestry, suggesting that a pure Floreana parent must have contributed to their lineage.
Scientists have proposed that sailors may have transported tortoises from Floreana or elsewhere and accidentally abandoned some near Wolf Volcano. Natural dispersal during extreme flooding has also been considered, although researchers cited by CNN believe human movement is the more plausible explanation.
The discovery transformed the conservation possibilities. Rather than trying to recreate an extinct population from nothing, scientists had living animals carrying part of its genetic legacy.
The lost tortoise finally gets another chance
That possibility has now led to one of the Galápagos' most ambitious restoration efforts. After years of breeding and raising Floreana-lineage tortoises at the Fausto Llerena Land Tortoise Breeding Center, 158 young tortoises were released on Floreana in February 2026. The animals are hybrids, not genetically pure Floreana tortoises, but they carry ancestry from the population that vanished from the island in the 19th century.
Scientists equipped the released animals with satellite-tracking devices to monitor how they adapt to their restored habitat. NASA-supported mapping also helped identify areas considered suitable for their release and future nesting.
Their return matters beyond the survival of one lineage. Giant tortoises are considered ecosystem engineers because their feeding, movement and digestion influence vegetation and seed dispersal. They can transport seeds across large distances, open up vegetation and create spaces used by other animals.
The tortoises that disappeared from Floreana may therefore have taken part of the island's ecological machinery with them.
Now, more than 150 years after their disappearance, their descendants are beginning to occupy that landscape again, turning a strange discovery on a distant volcano into a possible second chapter for one of the Galápagos' lost giants.
