The only known members of the giant Galapagos tortoise species Chelonoidis phantasticus were found 113 years apart. In 1906, a solo male was found wandering around Fernandina Island, but that would be the last science saw of the species until 2019 when researchers stumbled across a second lone ranger: a 50-year-old female that’s been nicknamed Fernanda, who appears to be queen of her own island.
The surprise discovery doubles the known members of C. phantasticus from one to two, but it’s also baffled evolutionary biologists as while their genomes proved to be very similar (the male now sits in the California Academy of Science) they look very different. Fernanda’s shell was comparatively small and smooth to that of the male, whose carapace protruded similarly to that of a saddleback tortoise.
Fernanda’s discovery is reported in a paper published in Communications Biology with the satisfyingly succinct title: The Galapagos giant tortoise Chelonoidis phantasticus is not extinct.
“The finding of one alive specimen gives hope and also opens up new questions as many mysteries still remain,” said senior author Adalgisa Caccone, a senior research scientist and lecturer in Yale’s Department of Ecology & Evolutionary Biology in a release.
“Are there more tortoises on Fernandina that can be brought back into captivity to start a breeding program? How did tortoises colonize Fernandina? And what is their evolutionary relationship to the other giant Galapagos tortoises?”
C. phantasticus was thought to have gone extinct due to volcanic activity on the remote Fernandina Island, believed to be the most inaccessible of the Galapagos Islands. Having seen around 25 volcanic eruptions in the last 200 years, and with little room for foraging or escape, it was expected to be a disastrous home turf for a slow-moving species like C. phantasticus, and yet Fernanda has been living it up on the island for half a century.
"The island one of the most recent in the Galapagos archipelago, and because it’s young - geologically speaking - it’s still very active in terms of volcanic eruptions," Caccone said to IFLScience.
"What that has done is constantly create new lava fields that are very difficult to pass. Even for humans to explore properly is really difficult, but for the tortoises it’s created isolated patches of suitable habitats so they can’t go from one place to the other."
Despite their similar genomes, the researchers spotted a few differences within the mitochondrial DNA (aka, the genetic code for “the powerhouse of the cell”) which is inherited from the mother. It could be, then, that some of their differences are due to Fernanda actually being a hybrid created from two Galapagos tortoise species, for example: a C. phantasticus male and a C. nigra female.
The latter is now extinct and originates from a different island, but it’s possible she could have vacationed in Fernandina (thanks to humans who moved the tortoises around) long enough to mate and leave her mitochondrial DNA for future generations to enjoy. The authors are eager to establish who the true C. phantasticus is, and if Fernanda is indeed a hybrid, but doing so requires more tortoises.
However, another reason for their differences could be due to the fact that life on Fernandina Island is tough.
"She is small. She is now in good health and alive and kicking, but she is a small adult which is why also morphologically she looks very different from the male specimen that we have in the museum," Caccone said. "It’s probably to do with stunted growth because the food isn’t there. This animal was segregated in a patch of vegetation, and that’s probably impacted her growth."
Despite the turbulent times at Fernandina, tortoise scats on the island suggest there could well be other Galapagos giants to find here. So, the Galapagos National Park and Galapagos Conservancy plan to go on a (non-violent) giant tortoise hunt in the hopes of finding some of Fernanda’s relatives and possibly even preserving the species.
However, Caccone fears that finding breeding-age individuals may only be half the battle. "The conservation issue we have is that if we do find more animals and start a breeding program, what are we going to do with them?" she said. "Their home is not suitable anymore."