include omnivores (rats and feral pigs), predators 

 (mongoose, foxes, and feral dogs and cats), and 

 herbivores (feral livestock and nonnative deer). 



WS has a long history of involvement in managing 

 invasive species, not only on the U.S. mainland, 

 but in Hawaii, the Caribbean, South America, 

 Africa, Indonesia, and the Philippines. Research 

 continues to improve methods and strategies to 

 (1) prevent introductions, (2) detect new introduc- 

 tions, (3) eradicate nonnative vertebrates already 

 established, and (4) support sustained control for 

 well-established invasive species where eradication 

 is not feasible. 



NWRC Biologists Develop and Test a Multiple- 

 Capture Trap for Nutria — An invasive aquatic 

 rodent from South America, nutria cause substantial 

 damage to marsh vegetation in many parts of 

 the United States. NWRC researchers designed 

 and tested a multiple capture trap (MCT) at the 

 Mandalay National Wildlife Refuge in coastal 

 Louisiana. Six MCTs were baited with food (carrots, 

 corn, and sweet potatoes), and six were baited with 

 fertilized marsh plants. 



During a 10-day trial, nutria were caught in both 

 types of MCT sets: 10 in the food traps and 12 

 in plant lure traps. As many as three nutria were 

 captured overnight in one trap. On two occasions, 

 nutria escaped the traps when approached by 

 a person. No nontarget animals were captured; 

 however, investigators suspected that swamp rabbits 

 were entering the MCTs to feed and then were able 

 to escape through the traps' one-way door. 



Using a FLIR (forward-looking infrared) unit at 

 night and motion-activated cameras, observers 

 saw several nutria around some of the traps, 

 but the animals were never caught. Clearly, 

 more-effective attractants for nutria need to be 

 developed before the MCT will be highly effective 

 in catching nutria. Additional field trials, perhaps 

 using nutria auditory cues, are planned to be 

 conducted in the Pacific Northwest. 





The nutria is an invasive aquatic rodent from South America. 

 (Photo courtesy of the U.S. Fish and Wildlife Service.) 



Researchers designed and tested a multiple-capture trap for 

 nutria in Louisiana. 



NWRC Biologists Study Wild Norway Rat Behavior 

 for Better Management Strategies — A better 

 understanding of invasive rat behavior would allow 

 for better detection of invading rats on islands and a 

 greater likelihood of rapid and successful eradication. 

 NWRC biologists used operant-conditioning behavior 

 paradigms to study wild Norway rats' rate of 



Developing Methods 31 



