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A giant Galapagos tortoise thought to be extinct has been found alive a century later. Only one specimen has been found, a female called ‘Fernanda’, but the comparison of its genome with that of the only known ancient specimen leaves no room for doubt: it is the same species.
The Galapagos giant tortoise from Fernandina Island (Chelonoidis phantasticus) is called ‘fantastic giant tortoise’ by the extraordinary shape of the shells of the males, which have an extreme flare along the outer edge and a conspicuous front part. Until now, only one specimen was known, a male collected during an expedition in 1906.
‘Fernanda’ was discovered in 2019 on the same island, an active volcano on the western edge of the Galapagos archipelago that is reputed to be the largest virgin island on Earth.
It appeared in a patch of vegetation in the middle of a sea of cold lava. So many environmentalists doubted that it was actually a turtle. phantasticus autochthonous It lacks the conspicuous flaring shell of the historic specimen, though scientists speculated that stunted growth may have distorted its features.
To definitively determine Fernanda’s species, Peter Grant, a professor of zoology at Princeton University, sequenced her entire genome and compared it to the genome he was able to recover from the specimen collected in 1906. He also compared those two genomes with samples from the thirteen other species of Galapagos tortoises, three individuals from each of the twelve living species, and one individual from the extinct C. abingdonii.
The results, to Grant’s own surprise, indicated that the two tortoises belonged to the same species, and both were “very different from all the tortoises on the other islands.” Scientists estimate that Fernanda is over 50 years old, but she is small, possibly because limited vegetation stunted her growth.
For Adalgisa Caccone, from Yale University and lead author of the article, “the discovery of a living specimen gives hope and also opens new questions”, since there are still many “mysteries” to be solved about the Galapagos tortoises, as if there are more specimens in Fernandina or how they colonized the island. Encouragingly, tracks and fresh droppings of at least two or three other tortoises have been found during other expeditions on the island.
shell shapes
Two or three million years ago, a storm swept one or more giant tortoises from the South American mainland to the west. Because they don’t swim, the tortoises bred only with others on their own islands, resulting in rapid evolution, following the pattern of the better-known Galapagos finches. Today, there are 14 different species of Galapagos giant tortoises, all descended from a single ancestor.
The diversification of Galapagos tortoises reveals a continuum of shell shapes, with the easternmost islands showing rounder, more domed shells, and the westernmost island, Fernandina, showing more elongated ones. Dome tortoises live in wetter, higher-elevation ecosystems, while their cousins inhabit drier, lower-elevation environments. All 14 are listed on the IUCN Red List as vulnerable, endangered, critically endangered, or extinct.
Turtle populations were decimated by European sailors who hunted them for food. “They were a great source of fresh meat for sailors, but that meant many of the species were severely overhunted,” says Gaughran. “And because they have such a long generation time, populations have a hard time recovering quickly.”
‘Fernanda’ is now at the Tortoise Center of the Galapagos National Park, a rescue and reproduction center, where experts are seeing what they can do to keep their species alive. “The discovery tells us about rare species that can persist in isolated places for a long time,” says Grant. “This information is important for conservation. It encourages biologists to search harder for the last individuals in a population to save them from the brink of extinction.”
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