Black Rat (Rattus rattus) Eradication from the San Jorge Islands, Mexico

SUMMARY Introduced commensal rats ( Rattus spp.) are a major contributor to the extinction and endangerment of island floras and faunas. The use of the toxin brodifacoum to completely eradicate rats from islands is a powerful conservation tool. However, brodifacoum is toxic to animals other than rats and on some islands its use may not be feasible without prohibitively expensive mitigation. As part of a regional conservation program, we experimentally tested brodifacoum and two less toxic rodenticides, diphacinone and cholecalciferol, in a Rattus rattus eradication on the San Jorge Islands, Mexico. All three rodenticides were successful in eradicating rats, suggesting that the less toxic diphacinone and cholecalciferol may be valid alternatives to brodifacoum for some island eradication programs. However, the choice of rodenticide must be balanced between efficacy and the risks to non-target species. Applied field research on less toxic rodenticides, as well as improving palatability of baits, is needed and may prove invaluable in facilitating the prevention of extinctions and the restoration of increasingly complex island ecosystems. We expect this conservation action to have an important and lasting impact on seabird and bat conservation in northwest Mexico. The San Jorge Islands are an important seabird colony, including colonies of brown boobies (