The Galápagos Islands are famous for their biodiversity, especially their giant tortoises. But around 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 host of invasive species, it was thought to be extinct.
In 2000, however, scientists made a shocking discovery: a population of tortoises 70 miles away on Isabela Island looked strikingly like the Floreana giant tortoise with their telltale saddle-shaped shells. Genetic testing confirmed these were hybrid tortoises descended from Floreana giant tortoises that must have accidentally wound up on the island after being put onboard 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 reared in a special captive breeding program.
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Floreana tortoises released back onto their native island.
Galápagos Conservancy
“Watching the tortoises step onto Floreana and start exploring was incredibly moving,” says James Gibbs, vice president of science and conservation for the nonprofit 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 paired adults collected from Isabela Island based on genetic testing to maximize their offspring’s Floreana ancestry. While the resulting animals are not exact genetic replicas of their ancestors, they do carry much of the original Floreana lineage, Gibbs says.
Galápagos Conservancy staff and Galápagos National Park rangers hike across the landscape, carrying tortoises in crates to the strategically selected release sites.
Galápagos Conservancy
In addition to being a win for the animals themselves, the tortoise’s return will also be a boon for the island, Gibbs says. The tortoise is a what is called a keystone species, dispersing seeds and helping to regenerate forests, so the hope is that its return will begin to push the island more closely toward 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," says Rick Hudson, president emeritus of the non-profit Turtle Survival Alliance, who was not involved in the research. After Aldabra tortoises were brought back to Mauritius, for example, native plants returned and introduced vegetation decreased. "Over time, the habitat begins to resemble its former state," Hudson says. "We expect similar results on Floreana."
“The island’s ecosystems and evolutionary lineage is restarting, and the biological processes that shaped Floreana are coming back again,” Gibbs says. “It’s a powerful reminder that sometimes what seems lost forever is simply awaiting the chance to return.”