A population of endangered giant tortoises has recovered on the Galapagos island of Española, returning from a point when the population was just over a dozen at one point. The lead study author, an ESF professor, described the finding as “a true story of success and hope in conservation.” The study was published on October 28, 2014.

Nearly 40 years after the first tortoises bred in captivity were reintroduced to the island via the Galapagos National Park Service, the endemic Española continue to reproduce and restore part of the ecological damage caused by feral goats that were introduced to the island in the late 19th century.

Professor of vertebrate conservation biology at ESF and lead author of the paper published in the journal “PLOS ONE,” James P. Gibbs, said in a statement, “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.”

Gibbs and fellow collaborators examined the tortoise population using 40 years worth of data from tortoises that were marked and recaptured repeatedly by the Galapagos National Park Service, Charles Darwin Foundation, and visiting scientists for measurement and monitoring.

Although the tortoise population is now stable, it is not expected to increase until more of the goat-inflicted damage to the landscape is resolved. The goats are now eradicated.

Gibbs said, “Population restoration is one thing but ecological restoration is going to take a lot longer.”

According to the World Wildlife Foundation, the giant tortoise weighs up to 700 pounds and can grow up to four feet long.