In the 1960s, with only 100 tortoises remaining, conservationists launched a concerted effort to preserve the species. The few unhatched eggs that could be found were carefully collected and incubated on another island, where they were hatched and raised for five years - until they were large enough not to be attacked by rats - before being released back on Pinzón. But the rodent problem still plagued any eggs that remained on the island.
Then, in 2012, biologists used helicopters to distribute poison designed to attract only rats. It was a first-of-its-kind operation, but it worked; Pinzón was recently declared rat-free.
"The incredible eradication of rats on this island, done by the park service and others, has created the opportunity for the tortoises to breed for the first time," says Gibbs.