Washington: Conservationists said on Tuesday they have brought giant tortoises found on the Galapagos island of Espanola back from the brink of extinction, gaining a foothold strong enough to allow humans to leave the reptiles alone.
Numbering just 15 some five decades ago, the tortoises, which can live as long as two centuries, now number about 1,000 and can sustain themselves, according to a study published in the scientific journal PLOS ONE.
"We saved a species from the brink of extinction and now can step back out of the process. The tortoises can care for themselves," said James Gibbs, a vertebrate conservation biology professor at the State University of New York (SUNY) College of Environmental Science and Forestry who led the study.
Located in the Pacific about 600 miles (1,000 km) west of Ecuador, the Galapagos archipelago is home to an array of unusual creatures that helped inspire Charles Darwin`s theory of evolution by natural selection following his 1835 visit.
Española giant Galapagos tortoises, their scientific name is Chelonoidis hoodensis, measure 3 feet (1 meter) long with a saddle-backed shell.
They live up to 150 or 200 years, eating grasses and leaves during the wet season and cactus during the dry season on an arid, low, rocky island measuring only 23 square miles (60 square km). Gibbs said the population numbered perhaps 5,000 to 10,000 tortoises before the arrival of people.
"The tortoises were hunted by buccaneers, whalers and other sea goers throughout the 18th and 19th centuries," added Linda Cayot, a herpetologist who is science advisor to the Galapagos Conservancy group.
"They collected them live, stacked them in their holds, and had fresh meat on their long voyages. Tortoises can live up to a year without food or water, so a natural source of fresh meat," she said.
Gibbs said the tortoises had been given up as extinct by the time the islands were protected as a national park in 1959.
In the 1960s, only 14 tortoises were found on Espanola, 12 females and two males. They were all taken into captivity and a third male was found in the San Diego Zoo. From those 15 tortoises, the population was rebuilt through a breeding program in captivity before they were reintroduced to the island.
"Nobody knew how to breed tortoises in captivity and the best zoos around the world had failed. The Galapagos National Park figured it out and actually became exceedingly effective at it," Gibbs said.
The success story of the Espanola subspecies comes in sharp contrast to the closely related tortoise found on the Galapagos island of Pinta. In 2012, a male dubbed Lonesome George died in captivity as conservationists tried in vain to find a way to breed him. He was the last of his subspecies.
Even though the human threat was eliminated by protecting the Espanola tortoise, the reptile still faced a formidable foe in goats that inhabited the island for 90 years before being removed in the 1970s.
Introduced to the island by humans, the goats mowed down just about everything in their path, including most of the cactuses the tortoises thrive on.
Unlike the grassy place it once was, the island now is covered with woody vegetation unsuited for tortoises. Gibbs said it could take hundreds of years for cactuses to reach previous levels.