A presumed-extinct giant tortoise of the Galápagos Islands was found alive in 2019, and a new DNA study confirms the female tortoise is the same species as an animal collected over a century ago. “Fernanda,” as she’s called, is the only living Fernandina Island tortoise (Chelonoidis phantastica) known and just the second member of the species ever recorded.
The Galápagos Archipelago — the cradle and testing ground for Darwin’s theory of natural selection — is bedazzled with giant tortoises, some of which have gone extinct since their discovery. The most famous of these animals is undoubtedly Lonesome George, the last (or ‘endling’) Pinta Island tortoise, who was around 100 years old when he died in 2012, marking the extinction of that species.
Fernanda (‘Fern’ for short) represented a shell-shocking discovery when researchers discovered her in 2019 on the volcanic island of Fernandina. Only now has a team of researchers extracted DNA from the tortoise and confirmed that she is indeed a Fernandina Island tortoise. Their study is published today in Current Biology.
“Because tortoises can occasionally move between islands, we weren’t sure if Fernanda was in fact a native Fernandina Island tortoise or if she had migrated to Fernandina from a different island in the Galápagos,” said Stephen Gaughran, a zoologist at Princeton University and co-author of the recent paper, in an email to Gizmodo. Though the tortoises cannot swim, they float (despite their heft) and can be carried to adjacent islands during severe storms. Humans have also moved tortoises between islands.
“To test this, we took a blood sample from Fernanda and sequenced her genome,” Gaughran added. “We then compared her genome to the genome of a museum specimen of a Fernandina tortoise collected over 100 years ago, and to the genomes of all other Galápagos giant tortoise species.”
The team’s analysis revealed that Fernanda was indeed the same species as the holotype specimen discovered in 1906, which until now was the only known Fernandina Island tortoise. The two tortoises were genetically distinct from the 12 extant tortoises of the Galápagos, as well as the extinct Pinta Island tortoise.
Peculiarly, the genetic analysis revealed that the Fernandina Island tortoises were most closely related to the Española Island tortoises, one of the farthest islands from Fernandina. How exactly Fernanda’s ancestors made it to the westerly volcano remains unknown.
Fernanda’s existence boosts hope that other Fernandina Island tortoises may still live. Fern is over 50, but small for her size, perhaps due to the scant vegetation available on Fernandina.
“At lower elevations, the vegetation occurs in island-like clumps in a sea of recently congealed lava,” said Peter Grant, an evolutionary biologist at Princeton University unaffiliated with the recent paper but who has worked extensively in the Galápagos, in a university release. “Fernanda was found in one of these, and there is evidence that a few relatives may exist in others.”
It’s not the first time a Galápagos tortoise species has been presumed extinct, only for evidence to contrary to appear. Ten years ago — the same year Lonesome George died — a team of researchers contended that the Floreana Island tortoise (Chelonoidis elephantopus) was likely still alive, based on genetic footprints of the species in hybrid tortoises.
Of course, we can never prove an animal is truly extinct — it’s more a very careful assumption that’s made after numerous searches come up empty. But several of the paper’s co-authors are planning expeditions to scour Fernandina for Fernanda’s relatives. Even one male tortoise would make the species’ recovery infinitely more likely, barring biological miracles.