Food and feeding habits of Eurasian otter, Lutra lutra, and American mink, Neovison vison, in an Atlantic island of northwest Spain

Abstract

Abstract. A small population of otter and mink coexist on the Isle of Sálvora, off the coast of Galicia, a region in northwest Spain. The aim of this study was to analyse the feeding habits of both species (taxa and type of prey) and their degree of trophic overlap. In order to analyse which habitat features best define otter and mink trophic preferences, fish preys were defined according to three criteria: substrate preference, position in the water column, and tidal zones. A total of 178 otter spraints and 158 mink scats were collected and analysed between May and October 2007. The relative frequency of occurrence and the biomass of each taxon were calculated. Mink consume mainly rabbits in spring, seagulls in summer, and rodents and shrews in autumn. The frequency of rabbits and gulls in mink diet was related to the abundance of both prey on the island. Otters were basically feeding upon fish throughout the study period. Their main prey was garfish (pelagic fish) during spring and summer, and Bleniidae and Gobiidae (benthic fish of rocky bottom pools) in autumn. These fishes are also consumed by mink during late summer, when the diet overlap between both species is higher (August diet overlap of 43.5 %, mean diet overlap of 16.4 %).