January 27, 2011 | 4
The Galápagos National Park Service has launched a project to protect the famous archipelago’s endangered species by wiping out introduced, invasive rats. As has been done in other locations, such as Australia’s Christmas Island, the Galápagos rats will be targeted with poison bait dropped from helicopters, starting on nine of the chain’s small and medium-sized islands.
The project actually got its start in 2008 with a pilot project on North Seymour Island. The poison there was dispersed by hand. The island has now been reported clear of rats.
According to a report from the Canadian Press, “The poisoned bait is contained in light blue cubes that attract rats but are repulsive for the sea lions and birds that also inhabit the islands.”
This time around, pilots will use GPS data to disperse the poisoned bait over the entire surface of the islands. The bait will be applied twice, seven days apart, with the goal of killing all of the rats on the islands during that time. The cost for this phase of the project is estimated at just under $1 million.
Once the rats are gone, a few other introduced species (plants and invertebrates) which have a lesser impact on the Galapagos ecosystems will also be targeted, although the methods of this targeting were not made clear.
According to the Galápagos Conservancy, scientists have performed a risk analysis to make sure that the poisoned bait will not affect the native species. Most of the native species, including mockingjays and Charles Darwin’s famous finches, would not be likely to consume the poisoned bait, but one species, the Galápagos hawk (Buteo galapagoensis), is considered at risk, because it could “capture and feed on rodents that have consumed the bait,” according to a prepared release from the Conservancy. To protect them, 20 of the hawks were captured from two islands and will be held in captivity for two months until neither the poison nor the rats pose a risk to the birds.
Three species of introduced rodents, which came to the islands on boats, can be found throughout the Galapagos, including the black rat (Rattus rattus) and Norway rat (R. norvegicus) and, to a lesser degree, the house mouse. They pose threats to tortoises, iguanas and 50 different land and sea birds by eating the eggs of the animals and by carrying parasites and disease.
Ironically, the extinction of a native Galápagos rodent was caused by black rats more than 75 years ago after the rats brought disease and competition for food and living space, according to the Galápagos National Park web site. The last Santa Cruz mouse (Nesoryzomys indefessus) was captured in 1934. Another rodent species, the Santiago mouse (N. swarthi) disappeared in 1906 and was believed to have gone extinct, but it was rediscovered in 1997.
(Another irony: eliminating cats from one island caused the rat population there to explode. Oops.)
The project’s manager, Victor Carrion, said it would take 20 years to fully clear the archipelago of invasive rats.
Photo: Rattus rattus by Alex O’Neal via Flickr, Creative Commons Licensed