Following an apparent increase of local population density of coypu (Myocastor coypus) in a Mediterranean remnant wetland, we developed a pilot study aimed to evaluate a specific control program. Inside the study area, we performed three transects per month from August 2008 to July 2009, grouping data in bimonthly periods. The water level in the study area showed a maximum in December–January, significantly decreasing from late spring to summer and significantly increasing from late summer to winter. Sampled individuals mainly occurred in Phragmites reed beds and in rush beds (dominance of Carex sp., Juncus sp. Bolboschoenus sp.). The index of mean relative density of coypu individuals ranged between 1.40 (February–March) and 5.72 (October–November) with an evident increase in late summer–autumn. During this period, mean density of runways was higher in reed beds than in rush beds, with differences tending to significance. In summer, the network of channels in reed beds, locally used for fishery farm, may maintain a water level suitable for the coypu. These results (preference for reed beds and increase of coypu density in late summer–autumn) should be considered when coypu populations are under control program, at least in the Mediterranean region where there is a scarcity of available data.