Fernanda, the only known living Fernandina giant tortoise, now lives at the Galápagos National Park’s Giant Tortoise Breeding Center on Santa Cruz Island. Credit: Galápagos Conservancy
A giant tortoise from a Galápagos species thought to be extinct for more than a century has been found alive. The 50+-year-old tortoise, named Fernanda after her Fernandina Island home, is the first of her species identified since 1906.
The Fernandina Island Galápagos giant tortoise (Chelonoidis phantasticus, or “fantastic giant tortoise”) was known only from a single specimen, collected in 1906. The discovery in 2019 of a female tortoise living on Fernandina Island provided the opportunity to determine if the species lived on.
Princeton’s Stephen Gaughran, a post-doc research fellow in evolutionary genomics, sequenced Fernanda’s complete genome and compared it with the genome he was able to recover from the museum specimen collected in 1906. Gaughran 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 C. abingdonii.
The genetic analysis showed the two known Fernandina tortoises are members of the same species, genetically distinct from all others.
When Fernanda was discovered, many ecologists doubted she was actually a native phantasticus tortoise. “Fantastic giant tortoises” get their name from the extraordinary shape of the males’ shells, which have extreme flaring along the outer edge and conspicuous saddlebacking at the front. Saddlebacking is unique to Galápagos tortoises, and the phantasticus tortoise shows it more prominently than the other species.
However, Fernanda lacks that saddleback—though scientists speculated her obviously stunted growth could have distorted her features. Tortoises can’t swim from one island to another, but they do float, and they can be carried from one Galápagos island to another during hurricanes or other major storms. There are also historical records of seafarers moving the tortoises between islands.
“Like many people, my initial suspicion was that this was not a native tortoise of Fernandina Island,” said Gaughran. “But then we saw—to my surprise—that Fernanda was very similar to the one that they found on that island more than 100 years ago, and both of those were very different from all of the other islands’ tortoises.”
Fernandina Island is largely unexplored due to extensive lava fields blocking access to the island’s interior. It is the highest of the Galápagos islands, geologically young, and is essentially a huge pile of jagged blocks of brown lava.
After the 1906 discovery of C. phantasticus, the species was not heard from again. In 1964, 18 scats attributable to tortoises were reported on the western slopes of the island. Scats and a possible visual observation from an aircraft were reported during the early 2000s, and another possible tortoise scat was seen in 2014.
Finally, Fernanda was spotted in 2019, and more recently, tracks and scat of at least 2 or 3 other tortoises were found during expeditions on the island. And more expeditions are planned to search the inaccessible interior of Ferandina Island.
Gaughran and his collaborators from Yale University and Newcastle University (UK) estimate that Fernanda is well over 50 years old. She is now at the Galápagos National Park Tortoise Center, a rescue and breeding facility, where experts are seeing what they can do to keep her species alive.
In the meantime, the scientists have related research to work on. Newcastle’s Evelyn Jensen, lead study author, said her team will continue their studies to understand how the Fernandina species fits into the evolutionary history of the Galapagos giant tortoises.
Gaughran, on the other hand, is developing a tool that analyzes DNA from ancient museum specimens so they can be compared with modern samples. Right now, he’s working with collaborators at Princeton to unravel the mysteries of seal and walrus evolution. Gaughran says his tool is flexible enough to work on almost any ancient specimen.
“The software doesn’t care if it’s a seal or a tortoise or human or Neanderthal,” he said. “Genetics is genetics, for the most part. It’s in the interpretation where it matters what kind of creature the DNA comes from.”