Effectiveness of coypu control in small Italian wetland areas

Introduced coypu (Myocastor coypus) damage crops and natural vegetation and undermine riverbanks. We controlled coypu with cage traps to protect vegetation in 3 wetlands in the Park of the Rivers Po and Orba (northwestern Italy). During a 3-year trial, coypu were controlled in the Natural Reserve of Valenza (NRV), an area with a low degree of colonization, but not in one with a high immigration rate. In NRV park wardens were involved for 18 man-days of work annually, and the cost was 1,518 Euros (1,867 U.S. dollars) per year. From 2001 a control program was carried on in the 3 areas. Removal densities (0.06–1.3 animal/ha) suggested that 2 trapping periods annually were adequate to slow down coypu population increase. The recovery of yellow waterlily (Nuphar lutea) in 3 plots and colonization of new ponds by vegetation indicated that coypu were maintained at a level sustainable for vegetation development.