A team led by Yale researchers has begun a breeding program to recover an extinct species.

Working with staff from Galápagos National Park and over 60 multinational researchers, the team hopes to reinstate a population of giant tortoises on Floreana Island belonging to the species C. elephantopus, whose last surviving members died around 1850. In a paper published on Sept. 13 in Nature Scientific Reports, the team presented genetic analyses on Isabela Island tortoises transported to a breeding facility and believed to share some genetic ancestry with the Floreana tortoises.

“Our work revealed that there are a number of tortoises with Floreana ancestry on Wolf Volcano [located on Isabela Island], which is very exciting,” co-first author Joshua Miller said. “Also, of 38 tortoises now in the breeding center we found that 23 have Floreana ancestry and are good candidates for including in a breeding program. This is a great starting point for restoration of the species.”

Miller said the data analyzed in the paper was collected on an expedition to the Galápagos that took place in 2015, the year he became involved with the project. The purpose of that expedition was to identify and transport saddleback turtles — turtles whose shells are characteristic of Floreana tortoises — from Wolf Volcano to a breeding facility on another island.

“We spent 10 days hiking and looking for tortoises on the side of a volcano, and when we found one that we thought had a good chance of having genetic ancestry from Floreana based on the unique shape of its shell, we would radio back to a ship and have the animal airlifted from the volcano by helicopter,” Miller said.

The collaboration between Yale researchers and Galápagos National Park staff began in 1994 when senior author Gisella Caccone GRD ’86 went on a Yale Educational Travel trip with her husband to the Galápagos Islands. On a guided tour, she saw a corral of turtles that had been confiscated from the pet trade where they had been illegally obtained, but were stagnating in isolation since park staff could not figure out their islands of origin. Caccone said that three years earlier, her husband had introduced himself as a geneticist to the herpetologist on staff and soon began working on genetically sequencing the turtles.

Caccone, the director of Yale’s Center for Genetic Analyses of Biodiversity, said the data from the study also reveal an interesting story that explains how Floreana tortoises ended up on Wolf Volcano.

“What we think happened was when the whalers and when the mariners were stopping on the islands, they stopped on the islands to take our tortoises with them in the hulls of the ships, because turtles don’t need water or food for up to six months so they were perfect,” she said. “Eventually, when the hulls were full of whales, they didn’t need the tortoises any more, and they dropped them somewhere in the water on their way back.”

Caccone described one incident in particular, corroborated by ship logs, in which a British warship, fleeing nearby French ships, dropped hundreds of Floreana tortoises into Banks Bay, offshore of Wolf Volcano.

Now that the turtles’ genomes have been sequenced and some have been transported to the breeding facility, the researchers’ next step is to engineer optimal matings to produce offspring that are even more genetically similar to Floreana tortoises.

“It’s a bit like being a matchmaker for the 23 tortoises,” Miller said.

But because tortoises have a generation time of 25 years and Floreana Island’s ecosystem has suffered in the absence of giant tortoises, Caccone said they will reintroduce the second-generation tortoises to the island, although they will not have pure Floreana tortoise DNA.

According to Yale postdoctoral fellow and co-first author Maud Quinzin, this strategy will let the tortoises play their vital ecological role on the island as soon as possible.

“Once reintroduced on the island, evolutionary processes will have the last word and ensure the population is fit to survive Floreana Island’s conditions, which we also ensure to be possible by maximizing the genetic diversity in the offspring,” she said.

Even after they prevent the species from becoming extinct, the researchers’ work is far from over. The ship and helicopter used to airlift and transport the tortoises to the breeding center only docked on the western side of Isabela Island, and Caccone’s team had previously discovered genetic relatives of another extinct species of giant tortoise on the island’s eastern side. This species, C. abingdoni, was famous for Lonesome George, an individual who was the last of his kind until his death in 2012.

“We hope that as soon as we have the funding to do it again, we’ll go on the eastern side and try to see if we can find the relatives from Lonesome George this time,” Caccone said.

Due to human interference on the islands, roughly 10 percent of the original tortoise population survives today.

Madeline Bendermadeline.bender@yale.edu | @maddiebender3