An endangered population of giant tortoises has recovered on the Galapagos island of Espanola. 
 
 Giant tortoises that were once driven to the brink of extinction on a tiny Galápagos island have made an amazing comeback, a new study reveals. 
 
 The tortoise population on the island of Española dwindled to just 15 animals in the 1960s, because of damage to their habitat caused by feral goats. Then, about 40 years ago, captive-bred tortoises were released on the island, and now there are about 1,000 of them living and breeding in the wild. 
 
 "It's one of the greatest conservation success stories," said James Gibbs, a conservation biologist at the SUNY College of Environmental Science and Forestry in Syracuse, New York. Gibbs led the study published today (Oct. 28) in the journal PLOS ONE. [See Images of a Giant Galapagos Tortoise] 
 
 Giant tortoises used to be found all over the world, but now, in the wild, they're found only in a few places, including the Galápagos Islands, the Seychelles and the Mascarenes. Whalers hunted the tortoises on Española for food. Fishermen later brought goats to the island in the late 1800s, devastating the native ecosystem and the tortoises along with it. By the 1960s, only a handful of the colossal reptiles were left. 
 
 To fix the problem, "the first order of business was to eradicate the goats," Gibbs told Live Science. Conservationists brought in trained gunmen on helicopters to hunt down and kill all of the goats. 
 
 Meanwhile, the Galápagos National Park Service reintroduced captive-bred tortoises to the island, and marked and recaptured them over the years. 
 
 In the study, Gibbs and his colleagues analyzed 40 years of data collected by the national park service, the Charles Darwin Foundation and other visiting scientists. They found that the tortoise population had stabilized. 
 
 "What we basically found over time is, about half of the tortoises that were released have survived," Gibbs said. "That’s actually pretty amazing." 
 
 And the tortoises are breeding. Some of the younger animals found in the last five to 10 years weren't bred in captivity, Gibbs said. The tortoise population is "very secure," he said, and probably doesn't need further human intervention. 
 
 To find out how the island's vegetation has changed over the years, the scientists measured the carbon content of the soil at different depths. They found that over the past 150 years or so, there's been a shift in the flora from grasses to small trees and shrubs. These woody plants prevent the growth of cacti, which are staples of the tortoise's diet, and make it harder for the animals to move around, the researchers said. 
 
 So even though the tortoises are rebounding, it will take a lot longer for the ecosystem to bounce back and the tortoise population can fully recover, Gibbs said. 
 
 Editor's Note: This article was updated at 11:40 a.m. ET on Oct. 29, to correct a statement about where giant tortoises are found in the wild. 
 
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 Giant Tortoises Gain a Foothold on a Galapagos Island 
 
 Ecosystem needs further repair 
 
 10/28/2014 
 
 A population of endangered giant tortoises, which once dwindled to just over a dozen, has recovered on the Galapagos island of Española, a finding described as "a true story of success and hope in conservation" by the ESF professor who is the lead author of a study published today (Oct. 28). 
 
 Some 40 years after the first captive-bred tortoises were reintroduced to the island by the Galapagos National Park Service, the endemic Española giant tortoises are reproducing and restoring some of the ecological damage caused by feral goats that were brought to the island in the late 19th century. 
 
 "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, a professor of vertebrate conservation biology at ESF and lead author of the paper published in the journal "PLOS ONE." 
 
 Gibbs and his collaborators assessed the tortoise population using 40 years of data from tortoises marked and recaptured repeatedly for measurement and monitoring by members of the Galapagos National Park Service, Charles Darwin Foundation, and visiting scientists. 
 
 But there is another side to the success story: while the tortoise population is stable, it is not likely to increase until more of the landscape recovers from the damage inflicted by the now-eradicated goats. 
 
 "Population restoration is one thing but ecological restoration is going to take a lot longer," he said. 
 
 After the goats devoured all the grassy vegetation and were subsequently removed from the island, more shrubs and small trees have grown on Española. This hinders both the growth of cactus, which is a vital piece of a tortoise's diet, and the tortoises' movement. Chemical analysis of the soil, done by Dr. Mark Teece, an ESF chemistry professor, shows there has been a pronounced shift from grasses to woody plants on the island in the last 100 years. 
 
 The shrubs and trees also inhibit the movements of the endangered waved albatross that breeds on the island. Gibbs said the plants make it difficult for the ungainly sea birds to take flight. 
 
 "This is a miraculous conservation success accomplished by the Galapagos National Park Service," said Gibbs, " but there is yet more work to fully recover the ecosystem upon which the tortoises and other rare species depend." 
 
 Gibbs' co-authors on the study are Elizabeth A. Hunter, an ESF alumna who is now a Ph.D. student at the University of Georgia; Kevin T. Shoemaker, an ESF alumnus who is now a research scientist at SUNY's Stony Brook University; Washington H. Tapia formerly of the Galapagos National Park Service; and Linda J. Cayot of the Galapagos Conservancy. The research was supported by the Galapagos National Park Service, the Galapagos Conservancy, the Prometeo Program of Ecuador's National Secretariat for Higher Education, Science, Technology and Innovation, and the U.S. National Science Foundation.
– A welcome piece of news for an endangered species: Giant tortoises' population on the Galapagos island of Española is now "very secure," researchers say. "The global population was down to just 15 tortoises by the 1960s. Now there are some 1,000 tortoises breeding on their own," says James P. Gibbs, a professor at SUNY College of Environmental Science and Forestry and the lead author of a study on the animals, calling the success "miraculous." "It's a rare example of how biologists and managers can collaborate to recover a species from the brink of extinction." The research covers 40 years of tracking tagged tortoises, notes SUNY ESF. Feral goats were introduced to the island in the 1800s, and they munched their way through much of its vegetation. As the threat to tortoises grew, the goats were killed off by gunmen in helicopters, LiveScience reports. Tortoises bred in captivity were introduced four decades ago, and scientists are now finding animals that were born in the wild. Humans can likely step aside now, says Gibbs. But hurdles remain: Goats ate the island's grassy plants, and the vegetation that has sprung up since has tended to be more woody. They block the tortoises' cactus meals from growing, and they make moving around a challenge. "Population restoration is one thing, but ecological restoration is going to take a lot longer," Gibbs notes. (Meanwhile, closer to home, debate has raged over tortoises' iPads.)