USDA National Wildlife Research Center Symposia


Date of this Version



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


A thriving population of Gambian giant pouched rats became established on Grassy Key, a 550-ha island in Florida, following escape(s) from an exotic pet breeder. After existence of the population was verified, computer models indicated that Gambian giant pouched rats could successfully invade a large portion of North America if they reached the mainland. This largest of rat species is highly prolific, and its dispersal to the mainland could result in substantial negative impacts to agriculture, environment, and wildlife. Additionally, Gambian giant pouched rats are known vectors of a variety of diseases transmissible to humans and livestock. The first action to counter the severe and immediate threat of dispersal was to rapidly develop the information necessary on which to base an eradication program. The information included detection and monitoring technologies, population indexing methodologies, population distribution, habitat preferences, trapping methodology, acceptance of bait matrices, and efficacy tests of toxicants, and bait stations that minimize exposure to native species. With these tools forming a foundation, a pilot eradication was funded for Crawl Key, a 150-ha key adjoining Grassy Key to which the species expanded its range. The aims of the pilot eradication were to test and fine-tune the methods prior to implementing full-scale eradication on Grassy Key. No Gambian giant pouched rats were found in two subsequent surveys of Crawl Key. Further surveys of Grassy Key were used to refine bait station densities for the full scale eradication effort implemented on Grassy Key in spring 2007. The eradication effort is on-going.