The Galápagos tortoise once thought extinct now roams free

180 years after it disappeared, a tortoise returns to its Galápagos home

By Rachel Nuwer edited by Andrea Thompson

The Galápagos Islands are known for their biodiversity, especially for their giant tortoises. But about 180 years ago, Floreana Island lost its unique tortoise, the Floreana giant tortoise (Chelonoidis niger). After it fell victim to the arrival of sailors, pirates and a number of invasive species, it was thought to be extinct.

In 2000, however, scientists made a shocking discovery: a population of turtles 70 miles away on Isabela Island looked strikingly like the giant Floreana tortoise with its telltale saddle-shaped shells. Genetic tests confirmed that these were hybrid tortoises descended from Floreana giant tortoises that must have accidentally ended up on the island after being put aboard a ship for food.

Now, for the first time in nearly 200 years, tortoises with Floreana ancestry have returned to Floreana Island, following the release last week of 158 individuals bred in a special captive breeding program.

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“Watching the turtles walk onto Floreana and start exploring was incredibly moving,” says James Gibbs, vice president of science and conservation for the non-profit Galápagos Conservancy. “It felt like the end of a 26-year effort, but at the same time a beginning.”

In the carefully managed breeding program, Gibbs and his colleagues mated adults collected from Isabela Island based on genetic testing to maximize their offspring’s Floreana ancestry. While the resulting animals are not exact genetic copies of their ancestors, they carry much of the original Floreana lineage, Gibbs says.

As well as being a gain for the animals themselves, the turtle’s return will also be a blessing for the island, says Gibbs. The turtle is a so-called keystone species, spreading seeds and helping to regenerate forests, so the hope is that its return will begin to push the island closer to its original ecological state.

“Any time you can return an ‘ecosystem engineer’ like giant tortoises to an environment where they once roamed, we expect good things to happen,” said Rick Hudson, president emeritus of the nonprofit Turtle Survival Alliance, who was not involved in the research. For example, after Aldabra tortoises were brought back to Mauritius, native plants returned and introduced vegetation declined. “Over time, the habitat begins to resemble its former state,” says Hudson. “We expect similar results at Floreana.”

“The island’s ecosystems and evolutionary lineage are restarting, and the biological processes that shaped Floreana are coming back,” says Gibbs. “It’s a powerful reminder that sometimes what seems lost forever is just waiting for a chance to come back.”

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