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 nutria (Myocastor coypus) is a large semi-aquatic rodent, declared as one of the 100 worst invasive species in the world by the IUCN Invasive Species Specialist Group in 2000. Through USDA Small Business Innovative Research Phase I (Mach 2004) and Phase II (Mach 2006) funding, Genesis is developing a new nutria rodenticide as an alternative to the currently-registered zinc phosphide bait. Our course of research and development is described herein: live-trapping, laboratory non-toxic choice studies, laboratory toxicity bioassays, and field toxicity studies. Two active ingredients and two bait types proved to be successful, however, only cholecalciferol in each of two bait types will be tested in future field studies.