U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



J. Blanco and A. Fernandes (Eds.), Invasive Species: Threats, Ecological Impacts and Control Methods. Nova Science Publishers, Inc., NY.


Many invasive rodents have become established in the United States and its territories. The species include several species of Rattus, house mice (Mus musculus), Gambian giant pouched rats (Cricetomys gambianus), ground squirrels (Spermophilus parryii), nutria (Myocastor coypus) and marmots (Marmota caligata). While most were introduced accidently, some were introduced for food or fur. Additionally, some native species of rodents have been placed on islands, at least on a temporary basis, to study rodent species interactions. These rodents have caused serious impacts to native flora and fauna, agriculture, and other resources. They have caused the extinction or many species of birds on insular ecosystems. Although many methods are used to control or eradicate introduced rodents, rodenticides and traps are the main tools. Since the early 1990s, agencies have been eradicating rodents from various islands, primarily for conservation purposes. Of about 27 eradication attempts, 22 (81%) appear to have succeeded with only about 5 failures. For several islands, however, it is too early to determine if the attempted eradication has been successful or not. In the case of failed eradications, rapid re-invasion by rodents from nearby islands may be the reason. Numerous additional eradications are planned. We review the introduced rodent species, their impacts, and eradications, both successful and unsuccessful that have occurred in the United States. Most eradications involved the use of the anticoagulant rodenticides diphacinone and brodifacoum. Rodenticides have been applied by hand-broadcast, bait station deployment, and aerial broadcast. We briefly review the strategies and methods used in eradication projects and the efforts to mitigate potential non-target and environmental impacts. Finally, we consider some of the remaining challenges in invasive rodent management and eradication in the United States, including the use of toxicants, land access, public attitudes, resource availability and monitoring difficulties.