On a bleak December afternoon in 1989, with the color drained from the skies of the Cambridgeshire Fens, the campaign to eradicate a large semiaquatic rodent called Myocastor coypus from the British Isles finally ended. An aged, fight-scarred male, which the previous night had made the fateful decision to climb onto a raft set for it by the Ministry of Agriculture, Fisheries, and Food, spent most of the day encaged in a steel live-trap before being humanely dispatched. A single close-range shot thus consigned the coypu, or nutria, to the memories of the few remaining "marshmen" – inhabitants of the windswept fens and an endangered breed themselves. But this event, played out against a backdrop of ancient reed beds and crumbling windmills, still stands out as a landmark achievement in conservation biology.