Long-term cost-effectiveness of coypu (Myocastor coypus) control in Piedmont (Italy)

We used the results of a permanent coypu control program to perform a cost-benefit analysis. The coypu colonization of Piedmont was followed by a constant increase of agricultural damage from 1997 to 2000, and its subsequent decrease from 2000 to 2005. Despite the increase of coypu's range, the control effort managed to stop the increase of the damage and start a gradual reduction in the period 2000-2002. This control effort kept on increasing until 2005 (when it was 7.5 times higher than in 2000), but its costs were compensated by the reduction of the damage. In 2005, the benefit-cost ratio was calculated to be 2.6:1 and 3.8:1, according to two different scenarios. Coypu are controlled in many countries so as to reduce the damage and to oppose the relative threat to biodiversity. The outcomes are often negative and this is probably due to the inadequacy of the efforts. In this study we illustrate a permanent control program which was implemented to limit the crop-damage in Piedmont and proved successful and cost-effective.