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article imageGiant tortoise species brought back from brink of extinction

By Martin Laine     Oct 29, 2014 in Science
A species of Galapagos giant tortoises that numbered just 15 individuals 50 years ago, now has a healthy breeding population numbering over a thousand. The news is a rare bright spot at a time when the outlook for many species is increasingly bleak.
The comeback of the Espanola Giant Galapagos Tortoise is the result of 40 years of cooperative effort by researchers from the SUNY College of Environmental Science and Forestry (ESF) in Syracuse, NY, the Galapagos National Park Service, the Charles Darwin Foundation, and several individual scientists, according to an article on the ESF website.
“The global population was down to just 15 tortoises by the 1960s,” said Prof. James P. Biggs, a vertebrate conservation biologist at ESF and lead author of a paper describing the project published this week in the journal PLOS One. “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.”
Those few surviving tortoises were moved to another island by the Galapagos National Park Service where they could be more closely supervised and encouraged to breed. The service also began eliminating a population feral goats that had been introduced to the island in the 19th century, and had devoured much of the island’s vegetation.
“They can literally turn a rich ecosystem into a dustbowl,” raid Prof. Gibbs in an article on the BBC website.
In 1973, the first of the captive bred tortoises were released on the island.
The goats posed a particular problem for the tortoises, because they competed for the same food source, a cactus that grows on the island.
During dry seasons, pads that fall from the trees become a major food sources for the tortoises. Once the goats polished off all the other vegetation on the island, they began gnawing on the bark and roots of the cacti.
“They would feast on the roots … and chew away at the bark, and eventually that would topple these cacti,” Gibbs said. “And then they would have a buffet of maybe 500-1000 years of cactus growth, demolished in a week or two.”
Restoring the island’s ecosystem is the next step in the project.
“This is a miraculous conservation success,” said Gibbs. “But there is yet more work to fully recover the ecosystem upon which the tortoises and other rare species depend.”
More about Galapagos giant tortoises, Galapagos National Park service, Suny Environmental Science and Forestry