The status of the Fernandina Island Galapagos giant tortoise (Chelonoidis phantasticus) has been a mystery, with the species known from a single specimen collected in 1906.
Fernanda, the only known living Fernandina giant tortoise (Chelonoidis phantasticus), now lives at the Galápagos National Park’s Giant Tortoise Breeding Center on Santa Cruz Island. Image credit: Galápagos Conservancy.
Fernandina Island is an active volcano that stands alone on western periphery of the Galapagos Archipelago and is reputed to be the largest pristine island on Earth.
Since 1906, evidence has accrued that a mysterious species of giant tortoise might exist on the island.
A single specimen of a species named Chelonoidis phantasticus (the fantastic giant tortoise) was collected by the explorer Rollo Beck during an expedition by the California Academy of Sciences in 1906.
Its fantastic nature is due to the extraordinary morphology of the male specimen, with extreme flaring of its marginal scutes and unusually prominent ‘saddlebacking’ of the front section of the carapace, unlike any other tortoise yet observed in Galapagos, or elsewhere on the planet as saddlebacking is unique to Galapagos tortoises.
Despite being known previously from only one specimen, the Fernandina tortoise has been considered to represent a distinct species.
In 2019, a surprise discovery triggered a wave of international news that the giant tortoises may yet survive on Fernandina Island.
Nicknamed Fernanda, a single female tortoise was found on the lower, northwestern flank of the volcano. She is likely well over 50 years old but is small with her growth stunted. She is now in captivity in the Galapagos National Park Tortoise Center.
Encouragingly, recent signs (i.e., tracks, scat) of at least 2-3 other individuals were found during other expeditions on the island.
“For many years it was thought that the original specimen collected in 1906 had been transplanted to the island, as it was the only one of its kind,” said Professor Peter Grant, an ecology and evolutionary biologist who has spent more than 40 years studying evolution in the Galapagos islands.
“It now seems to be one of a very few that were alive a century ago.”
“Like many people, my initial suspicion was that Fernanda was not a native tortoise of Fernandina Island,” said Dr. Stephen Gaughran, a postdoctoral researcher at Princeton University.
To determine Fernanda’s species definitively, Dr. Gaughran and colleagues sequenced her complete genome and compared it to the genome they was able to recover from the specimen collected in 1906.
They also compared those two genomes to samples from the other 13 species of Galápagos tortoises — three individuals from each of the 12 living species, and one individual of the extinct Pinta giant tortoise (Chelonoidis abingdonii).
Their results show that the two known Fernandina tortoises are from the same lineage and distinct from all others.
“What comes next for the species depends on whether any other living individuals can be found,” said Dr. Evelyn Jensen, a researcher at Newcastle University.
“If there are more Fernandina tortoises, then a breeding program could start to bolster the population.”
“We hope that Fernanda is not the ‘endling’ of her species.”
A paper on the findings was published in the journal Communications Biology.
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E.L. Jensen et al. 2022. The Galapagos giant tortoise Chelonoidis phantasticus is not extinct. Commun Biol 5, 546; doi: 10.1038/s42003-022-03483-w
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