USDA National Wildlife Research Center Symposia


Date of this Version

August 2007


Published in: Witmer, G. W., W. C. Pitt, and K. A. Fagerstone, editors. 2007. Managing vertebrate invasive species: proceedings of an international symposium. USDA/APHIS Wildlife Services, National Wildlife Research Center, Fort Collins, Colorado, USA. Also available online at


The introduction of rodents on an island as a new predator usually interferes with natural island biodiversity, particularly on islands without any native mammalian predators. Many Alaskan islands, and most islands in the Aleutian Island region of the Alaska Maritime National Wildlife Refuge (AMNWR), are free of mammalian predators and are vulnerable to invasion by rodents. Rat introduction to islands can put ground-nesting birds, such as seabirds and endemic landbirds, at risk of extirpation. The refuge is also concerned about additional introductions of house mice. As far as we know, the introduction, or “spilling,” of rats onto refuge islands from ships and cargo was accidental, but probably preventable. This paper is about preventing new rodent invasions, especially rats, on Alaskan islands from shipwrecks, and using our experience on AMNWR as a basis for recommendations about improvements in the future.