The Galapagos Islands have seen their native plant and animal species dwindle as a result of invasive rats, but a new plan initiative will attempt to rid the islands of these invaders.
In the 17th and 18th centuries, whalers and privateers inadvertently introduced the black rats and mice to the Galapagos. In the 1900s, the rats were still being introduced to the new islands in the Galapagos. By this time, brown rats were also being introduced, further threatening the islands’ biodiversity.
Since then, both black and brown rats, wreak havoc among the wildlife of Galapagos by preying on eggs and hatchlings of bird and reptile species, to such an extent that one species of Galapagos tortoise has had no natural recruitment for nearly a century, and some unique bird species have become critically endangered. Their control and possible eradication in specific sites is a major priority for conservation in the islands.
Recent successes in rodent eradications on a number of small- and medium-sized islands in the Galapagos Islands have provided conservation managers sufficient knowledge and expertise to carry out the planned rat eradication on Pinzón Island, with little risk to native fauna and flora. This represents the largest island within the archipelago from which rats will be completely removed.
Rat traps and bait were dropped in 2011, but now poison will be spread in an attempt to rid the islands of almost 180 million rats that have now taken over and endangered the local environment.
According to the Galapagos Conservancy, the rats have prevented the giant tortoises on Pinzón from successfully reproducing in the wild for nearly 150 years, due to their predation on tortoise eggs and hatchlings. For the past 45 years, the Galapagos National Park Service (GNPS) and Charles Darwin Foundation have collected eggs, and artificially incubated, hatched, and raised the young in captivity. At four years of age, the young are considered “resistant” to attack by rodents and can be returned to their natural habitat.
Since the first reintroduction of 20 young Pinzón tortoises in 1970, more than 550 juvenile tortoises have been released on the island. The rodent bait being used in the eradication project does not pose a risk to the tortoises.
Other tests were performed before the eradication, in order to determine whether it was necessary to modify the existing bait formulas to increase their effectiveness and/or to reduce their attraction of non-target species.
Removing introduced rats from the islands is extremely important for the ecological restoration of Galapagos ecosystems, which still retain 95% of their original flora and fauna despite the presence of introduced species.