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Scientists hope to bring back extinct tortoise

By Sandra Blakeslee

The New York Times

The dodo is dead. The passenger pigeon has passed on. But Lonesome George, the iconic Galapagos tortoise whose death marked the end of his species, is in post-mortem luck.

A scientific expedition has discovered some of his close blood relations alive and well. With careful breeding, biologists now hope to revive George’s species and reintroduce the tortoises to the island on which they evolved.

It would be a signal achievement in a place that gave rise to our understanding of evolution and speciation.

Originally there were at least eight species of Galapagos tortoise, scientists now believe. (One was discovered only this year.) At least three species are extinct, including tortoises on Pinta Island. The last one, George, was discovered wandering alone in 1972 and taken into loving custody. His death, in 2012 at more than 100 years old, was a powerful reminder of the havoc visited by humans on delicate ecosystems worldwide over the past two centuries.

Tortoise numbers plummeted from more than 250,000 in the 16th century to a low of around 3,000 in the 1970s. In the 19th century, whalers, pirates and other seafarers plucked the animals from their native islands for use as ballast and food on long journeys. Tortoises can live in a ship’s hold for more than a year without food or water, making them the perfect takeaway meals.

There are two types of Galapagos tortoises: saddlebacked and domed. The sailors much preferred the smaller saddlebacks, which were easier to lug around and said to taste better.

Saddlebacked tortoises disappeared from Santa Fe Island and Floreana Island, a favorite hangout for sailors posting letters for other ships to carry home. With George’s death, the Pintas were gone, too.

But now the story of extinct Galapagos tortoises has taken a strange, and hopeful, twist.

More than a century ago, it turns out, sailors dumped saddlebacked tortoises they did not need into Banks Bay, near Wolf Volcano on Isabela Island. Luckily, tortoises can extend their necks above water and float on their backs. Many of them made it to shore, lumbered across the lava fields and interbred with Isabela’s native domed tortoises.

In 2008, scientists tagged and collected blood samples from more than 1,600 tortoises living on the flanks of the volcano. Back in the laboratory, there was a genetic eureka: Eighty-nine of the animals were part Floreana, whose full genetic profile DNA had been obtained from museum samples.

Some had genes indicating their parents were living purebred Floreana tortoises, hinting that the species might not be extinct after all.

Seventeen tortoises were shown to have high levels of Pinta DNA. Tortoises can live for more than 150 years, so some of them might well be George’s immediate next of kin.

Last month, scientists went back to find them. Their plan was to capture and separate tortoises with high levels of Pinta and Floreana DNA, and then breed animals that are genetically closest to the original species.

In just a few generations, it should be possible to obtain tortoises with 95 percent of their “lost” ancestral genes, the scientists said.

“The size of this population is mind-boggling,” said Adalgisa Caccone, a senior research scientist at Yale University and the expedition’s geneticist, said of the Wolf tortoises. “I am optimistic that some of these animals will have high conservation value.”

Genetics is increasingly a key component of conservation management worldwide, said Linda Cayot, science adviser for the Galapagos Conservancy, which helped sponsor the expedition with the Galapagos National Park Service.

But “this is the first time that genetic information has been used so determinedly,” she said, to manage a species and its environment.