A species of giant tortoise thought to have been extinct for more than a century has been discovered alive and well on a tropical island.
The Fernandina Island Galápagos giant tortoise (Chelonoidis phantasticus, or “fantastic giant tortoise”) was once known from only a single specimen, collected during a scientific expedition in 1906.
This happened until 2019, when a female giant tortoise named Fernanda was found on Fernandina Island.
Scientists from Princeton University and the California Academy of Sciences extracted Fernanda’s DNA along with that of the 116-year-old male.
In a paper published today in Communications Biology, the researchers reveal that the two are Chelonoidis phantasticus tortoises, genetically distinct from all other species of the Galápagos giant tortoise.
Fernanda, the only known living Galápagos giant tortoise on Fernandina Island, was found in a cluster of vegetation in a sea of solidified lava in February 2019
The Fernandina Island Galápagos giant tortoise was once known from only a single specimen, collected during a scientific expedition in 1906 before Fernanda was discovered
Peter Grant, Professor of Zoology at Princeton University and lead author, said: “For many years it was assumed that the original specimen collected in 1906 had been transplanted to the island as the only one of its kind.
“It now appears to be one of the few that lived a century ago.”
Fernandina Island is an active volcano on the west side of the Galapagos Islands that Charles Darwin visited in 1835 to inspire his theory of evolution.
After the 1906 discovery, slight evidence of living turtles was found from Fernandina Island, for example 18 droppings were seen on the western slopes of the island in 1964.
Other droppings and a possible visual observation from an airplane were reported in the early 2000s, and another possible turtle droppings was seen in 2014.
Fernanda was found in a vegetation group in a sea of solidified lava in February 2019.
Scientists estimate it is well over 50 years old, but it is small, possibly because limited vegetation stunted its growth.
When Fernanda was first discovered, many ecologists doubted that she was actually a native Phantasticus tortoise.
It does not exhibit the unique flare on the outer edge of its saddle back shell seen on the specimen collected by explorer Rollo Beck in 1906.
Saddlebacking is unique to Galápagos tortoises, and the Phantasticus tortoise displays it more clearly than the other species.
Fernanda may also have been transported from elsewhere, as turtles, although unable to swim, can drift between islands during a hurricane or storm, or be carried by sailors.
Stephen Gaughran, a postdoctoral researcher in ecology and evolutionary biology at Princeton, said: “Like many others, my initial suspicion was that this was not a native Fernandina Island turtle.”
A male specimen of the Fernandina Island giant tortoise was collected by explorer Rollo Beck during an expedition in 1906 and for years was the only evidence of the species’ existence
Scientists estimate that Fernanda is well over 50 years old, but she is small, possibly because limited vegetation on the volcanic Isla Fernandina stunted her growth
Fernandina Island is an active volcano on the west side of the Galapagos Islands that Charles Darwin visited in 1835 to inspire his theory of evolution
Grant and his team sequenced Fernanda’s genome from a blood sample and compared it to that of the museum specimen and the other 13 species of Galápagos giant tortoises to rule them out.
Gaughran added: “We saw, to my surprise, to be honest, that Fernanda was very similar to the one they found on this island more than 100 years ago, and both were very different from any turtle on the other islands.”
Yale University senior author and research scientist Adalgisa Caccone said, “The finding of a living specimen offers hope and also raises new questions, as many mysteries remain.
“Are there more turtles 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 Galapagos giant tortoises?
“This also shows how important it is to use museum collections to understand the past.”
While the island has remained largely unexplored due to extensive lava fields blocking access to its interior, more excrement and some traces of at least two other turtles have been found during recent expeditions.
Evolutionary biologist Peter Grant says that Fernanda’s genome shows that Chelonoidis phantasticus is the product of a mixture of different Galápagos species.
He said: “The next of kin are not on the next very big island, Isabela, but on another one, Española, far away on the other side of Isabela.
“The question of how the ancestors got to Fernandina remains open.”
Fernanda is now at the Galápagos National Park Tortoise Center, a rescue and breeding facility on Santa Cruz Island, where experts are seeing what they can do to keep their kind alive, including trying to find a male mate.
Grant added: “The discovery informs us about rare species that can exist in isolated locations for long periods of time.
“This information is important for nature conservation.
“It spurs biologists to look harder for the last few individuals in a population to save them from extinction.”
Right now, Fernanda is in a similar position to Lonesome George, who was famous for being the last of the Pinta Island Galapagos giant tortoises.
Lonesome George spent his last decades in captivity but was never bred and his species became extinct after his death of old age in 2012.
HISTORY OF THE GIANT TORTOISES IN THE GALAPAGOS ISLANDS
Two or three million years ago, a storm carried one or more giant tortoises west from mainland South America
Since they don’t swim, the turtles only breed with others on their own islands, leading to rapid evolution
Today there are 14 different species of Galapagos giant tortoises, all descended from a single ancestor
Turtles from the easternmost islands display rounder, more domed carapaces, and the westernmost island, Fernandina, displays the most dramatic saddleback
Raised and flared edges, saddleback shells are combined by long limbs and neck on the turtle
The dome turtles live in wetter ecosystems at higher elevations, while their saddleback cousins inhabit drier environments at lower elevations
All 14 species are listed as either Vulnerable, Vulnerable, Critically Endangered or Extinct on the IUCN Red List
This is because turtle populations were decimated by European seafarers who hunted them for food
They discovered they could keep turtles alive on their ships with minimal effort since the reptiles could survive on little food or water
Due to the long time between turtle generations, populations cannot quickly recover from such impoverishment
There are 13 different species of Galápagos giant tortoises in the cluster of 21 islands