In a rare story of conservation success, the giant tortoise is on the rise again in the Galapagos island of Española, after its numbers were severely reduced by the introduction of feral goats in the 19th century.

The article detailing the success in stabilizing the tortoise population was published today, October 28, in the journal PLOS ONE.

"The global population was down to just 15 tortoises by the 1960s. Now there are some 1,000 tortoises breeding on their own. The population is secure. It's a rare example of how biologists and managers can collaborate to recover a species from the brink of extinction," said James P. Gibbs, the lead author of the paper.

Forty years ago, after the giant tortoise had already been declared extinct, the Galapagos National Park Service sent conservationists out into Española island to look for surviving tortoises. The conservationists found the 15 remaining giant tortoises and bred them in captivity until their numbers increased. When they had 2,000 tortoises, they re-introduced them to the island in 1975. Now, almost forty years later, the population is stable, according to this new research paper. This is the first comprehensive look at the tortoise population since then.

"To me, it's been a quiet but remarkable success story in conservation, mostly because nobody's ever taken the time to synthesize the results of this massive effort," said Gibbs.

Half of the 2,000 tortoises introduced to the island in the 1970's are still alive, and they are breeding independently. Gibbs noted that the population could now thrive without further human intervention.

The tortoise population originally dwindled because early human arrivers to the Galapagos Islands brought goats, which ate the grass tortoises needed to survive, destroying the island of Española. Conservationists finally eradicated the last of the goats from the island in the '90s.

Another species of tortoises in the Galapagos islands, Pinta tortoises, went extinct in 2012 after the last remaining tortoise, named Lonesome George, died. Now, conservationists are hoping to use the same technique used on the Española tortoises to introduce a breed of Pinta tortoise hybrids recently discovered onto Pinta Island.

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