The coypu (or nutria) and muskrat are two alien rodent species that were brought to Europefor their pelts. Having returned to the wild, they do not compete with native species (at leastno study has shown this). On the other hand, they cause substantial damage to crops, riverbanks and river engineering works. That is why they have been classified as "vertebrate pests"and "game vermin" and French law has allowed them to be trapped and poisoned since 1979.This special situation set the guiding thread of our research, that is, the idea that people'srepresentations of these animals cannot be separated from their representations of themeasures that are taken to control them.These pest control actions are relatively old, and the light that we shed on them could beextended to other invasive species. We show how they are organised in conjunction with twotypes of player – professionals and volunteers – and fit into two different worlds, namely,farming and trapping (or hunting), the former having given priority to chemical control andthe latter to mechanical control methods.Opposition to the application of toxic chemicals in the wild is increasingly frequent today.This led us to follow in real time the public debates that emerged in 2002 about the choicebetween traps and poison. This also gave our study an applied facet. Various questionseffectively deserve to be asked, for example, "On what level should legislation be passed?With regard to which territories ? Who should carry out the control measures and whattechniques should be preferred ?" These questions are linked to each other and our studycannot give any definitive answers to them. On the contrary, it reveals their complexity. Fromour observations it appears that trapping is not a "simple" alternative to chemical control andcan have some unforeseen effects.Switching from poisoning to trapping ultimately means sticking to an increasinglystandardised technical approach that is out of phase with people's myriad representations ofcoypus and muskrats. These rodents are effectively seen to be scourges, but also cute animals,familiar animals, natural animals, wild animals, etc. These different representations can beexpressed simultaneously by the same group, even by the same person, and the dissonancethat our findings reveal raises the following fundamental question : With which animals dowe wish to live in our modern society and what identities do we give them ?Our research was based on non-directed interviews of seventy-nine people whom we met inthe course of four field missions carried out in the Poitou Marsh, Camargue, Brittany, theLoire Country, and northern France and belonged to the following groups : agriculturalextension workers and technical organisations, wildlife managers, naturalists and/or scientists,administrators and policy-makers, hunters, trappers, and farmers. Our study also entailedbibliographic research (a search through the scientific and grey literature) and an eighteenmonthreview of the regional press.