When Lonesome George died in 2012, it was thought that so did the last Pinta Island giant tortoise. Discovered roaming the rocky island in the Galapagos archipelago on his own in 1972, it was believed that he was the last of his subspecies. Despite a global search to find him a mate, it proved fruitless over the 80 years of his life. Now, Yale researchers think that his DNA might live on (or at least that of his relatives), diluted in hybrid tortoises found on another island descended from tortoises thrown overboard 150 years ago.
The tortoises, originally found living on seven of the Galapagos Islands, are divided into 15 subspecies, of which only 11 survive to this day. In addition to the subspecies from Pinta, those from the island of Floreana are thought to have become extinct in the mid-1800s. Unfortunately for the tortoises, they were easy prey to catch and survived for up to a year upside down in the holds of whaling and pirate ships, providing the sailors with fresh meat for their long voyages. This led to the tortoise population crashing from an estimated 250,000 in the 16th century to just 3,000 by the 1970s.
Divided into two different types depending on the shape of their shell, the tortoises are known as either domed or saddlebacked. It was these differences in shell morphology that first alerted the researchers to the potential that Pinta and Floreana tortoises, both of which were saddlebacked, might survive.
Giant galapagos turtle munching on Floreana. Fotos593/Shutterstock.
On another of the Galapagos Islands, this time Isabela Island, one of the subspecies living on the side of Wolf volcano was thought to occur in both saddlebacked and domed forms. But after taking blood samples from over 1,600 members of this population, researchers found something surprising. The saddlebacked varieties actually turned out to be hybrids, between the original Wolf volcano subspecies and those from Pinta and Floreana. Some have such a high percentage of DNA from these extinct subspecies that the scientists suggest their parents could have been purebred animals.
Now researchers have captured and airlifted 32 of the tortoises with the most distinctive saddlebacks and taken them to the breeding center on Santa Cruz Island, in the hope that they will harbor the largest proportion of the thought-to-be-extinct subspecies' DNA. First, the scientists want to conduct more tests to separate out those descended from Pinta and those from Floreana, and then breed the ones with the highest percentage from each island. This may allow them to bring back tortoises that they argue could eventually be as high as 95 percent purebred. They then plan on releasing them back onto the original island from which their ancestors came.
But how did the original purebred tortoises get so far from the islands on which they originated? Well, it’s suspected that as whaling and pirate ships passed this corner of Isabela Island, they probably jettisoned the animals into the sea when they realized they could not carry them. Surprisingly good swimmers, and able to keep their long necks above the water, the tortoises would have swam to the nearest land. So despite eating their relatives to extinction, the sailors might have inadvertently saved the species.