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


Date of this Version

Summer 2012


Wildlife Professional, Summer 2012: 33-34.


Invasive rodent species occupy more than 80 percent of island groups worldwide, with devastating impacts to native flora and fauna. Rodents prey on birds, mammals, reptiles, amphibians, and invertebrates, and indirectly effect native wildlife by destroying plants, competing for food, and transmitting disease. Species such as Norway rats (Rattus norvegicus), black rats (R. Rattus), and Polynesian rats (R. exulans) have caused the extinction of several species of native birds, mammals, and lizards (Atkinson 1985). For example, less than a decade after black rats were accidently introduced to Big South Cape Island in New Zealand in the early 1960s, one bat species- the greater short-tailed bat (Mystacina robusta)- and five bird species, including the South Island snipe (Coenocorypha iredalei), went extinct (Bell 1978).

To protect natural resources from rodents, biologists and landowners have typically applied anticoagulant rodenticides through bait stations. Though such stations can effectively eradicate rodents in small areas, they have not been feasible or effective in larger areas or on inaccessible islands. In 2005, USDA-APHIS Wildlife Services, in collaboration with the U.S. Fish and Wildlife Service (FWS) and two private companies, achieved a breakthrough in large-scale rodent eradication by developing and registering three new anticoagulant rodenticide products- Diphacinone 50 Conservation, Brodifacoum 25W Conservation, and Brodifacoum 25D Conservation- for broadcast application, both by hand or by air. To date, these products have helped successfully eradicate rodents from numerous islands in California, Florida, Alaska, Hawaii, and through the Virgin Islands, American Samoa, and the Pribilof Islands. Once the rodents were gone, the recovery and restoration of wildlife on these islands has been dramatic.