Coypu (Myocastor coypus) as ecosystem engineer: composition, size, and density of platforms in a Mediterranean coastal wetland

Coypu (Myocastor coypus) was recognized as ecological engineer for its ability to alter wet habitats and build structures throughout its life cycle. Platforms still represent poorly studied structures built by this rodent for various purposes, including reproduction, resting and thermoregulation. In order to obtain data on plant composition, size and density on the territory of coypu's platforms, we carried out a study in a Mediterranean wetland reed bed, stratifying data on two sub-habitat types (back dune and canal banks). Platforms were composed exclusively of common reed (Phragmites australis) stems, leaves, and inflorescences; they were elliptical in shape, and significantly higher in the back dune than on the canal banks. Density of platforms was higher in the back dune than on the canal banks. Platforms have been used as resting and feeding sites, as showed by drone images and remnants of red swamp crayfish (Procambarus clarkii). More than 40% of coypu's platforms along the canal banks showed traces of birds, suggesting an opportunistic use by waterfowls and waders. In this regard, platforms may be considered "key structures", locally increasing habitat heterogeneity. In a limited number of back dune platforms, remnants of plastic litter have been detected. The use of drone flights over wetlands may be useful to check the spatial pattern of coypu's platforms, especially in hard-to-reach areas. Ecological and management implications of our data have been reported.