Nearly 22 tonnes of poisoned bait are to be dropped on islands to kill rats that threaten bird and reptile species
Ecuadorian authorities have begun dropping nearly 22 tonnes of poisoned bait on the Galapagos Islands in an attempt to eradicate hundreds of millions of rats which threaten the archipelago's unique bird and reptile species.
The invasive Norway and black rats, introduced by whalers and buccaneers beginning in the 17th century, feed on the eggs and hatchlings of the islands' native species, which include giant tortoises, lava lizards, snakes, hawks and iguanas. Rats have also depleted plants on which native species feed.
The rats have left bird species critically endangered on the 19-island cluster 600 miles (1,000km) from Ecuador's coast.
"It's one of the worst problems the Galapagos have. [Rats] reproduce every three months and eat everything," said Juan Carlos Gonzalez, a specialist with the Nature Conservancy involved in the Phase II eradication operation on Pinzon island and the islet of Plaza Sur.
Phase I of the anti-rat campaign began in January 2011 on Rabida island and about a dozen islets, which like Pinzon and Plaza Sur are uninhabited by humans.
The goal is to kill off all non-native rodents by 2020, beginning with the Galapagos' smaller islands, without endangering other wildlife. The islands where humans reside, Isabela and Santa Cruz, will come last.
Previous efforts to eradicate invasive species have removed goats, cats, burros and pigs from various islands.
Pinzon is about 1,812 hectares (4,500 acres) in area, while Plaza Sur encompasses just 9.6 hectares.
"This is a very expensive but totally necessary war," said Gonzalez.
The rat infestation has now reached about 10 per square metre (one per square foot) on Pinzon, where an estimated 180 million rodents reside.
The director of conservation for the Galapagos National Park Service, Danny Rueda, called the raticide the largest ever in South America.
The poisoned bait, developed by Bell Laboratories in the United States, is contained in light blue cubes that attract rats but are repulsive to other inhabitants of the islands. The one-centimetre-square cubes disintegrate in a week or so.
The park official Cristian Sevilla said the poison would be dropped on Pinzon and Plaza Sur until the end of November.
A total of 34 hawks from Pinzon were trapped in order to protect them from eating rodents that consume the poison, Sevilla said. They are to be released in early January.
On Plaza Sur, 40 iguanas were also captured temporarily for their own protection.
Asked whether a large number of decomposing rats would create an environmental problem, Rueda said the poison was specially engineered with a strong anti-coagulant that would make the rats dry up and disintegrate in less than eight days without a stench.
It will help that the average temperature of the islands is 24C (75F), he added.
The current $1.8m phase of the project is financed by the national park and nonprofit conservation groups including Island Conservation.
The Galapagos were declared protected as a Unesco natural heritage site in 1978. In 2007, Unesco declared them at risk due to harm from invasive species, tourism and immigration.