Defeat of plague of 'pirate' rats that drove Galápagos giant tortoises to edge of extinction

For the first time in a more than a century, officials have confirmed that several giant tortoises from the critically endangered species C. duncanensis have been born naturally on an island in the Galápagos archipelago.

The introduction of black and brown rats to Duncan Island – otherwise known as Pinzón Island - some time before 1900 had caused the tortoise population there to fall into decline. But in 2012, National Park authorities began a rodent eradication program, which involved dropping poison at various sites from a helicopter.

"The presence of the black rat on Duncan Island caused the decline of species such as the Galápagos pigeon, lizards, snakes and the giant tortoise, which could not be born naturally because rodents ate their eggs", Danny Rueda, director of Ecosystems at the Galápagos National Park told Spanish news agency EFE.

The eradication program also involved temporarily capturing and removing a number of hawks from the island in order to avoid them eating any poisoned dead rats.

According to Rueda, in 2014 the island was declared free of rodents and, following an ecological monitoring survey carried out in December 2015, researchers have now confirmed the birth of baby tortoises in the wild for the first time in more than a century.

It is thought that rats first arrived on Duncan island on board pirate and whaling ships in the 1800s. Rueda says the biggest challenge now is to avoid the reintroduction of the rodents.

In 1965, the Galápagos National Park began a successful captivity breeding program with the 20 tortoises that were living on the island at the time, which was responsible for releasing 837 individual animals into the wild. Researchers hope that this program will no longer be necessary now that the tortoises are breeding naturally again.