Diet of Eurasian otters (Lutra lutra) in natural habitats of the Gemenc Area (Danube-Drava National Park, Hungary) in early spring period

Abstract

The relationship between the food web and interspecific trophic levels are less well understood along the Hungarian section of the Danube River. In this study, the diet composition of the Eurasian otter (Lutra lutra) as mammalian top predator species of wetlands was examined by spraint analysis, in an early spring period at six oxbow lakes of the Gemenc Area. The primary food of otters was fish (min-max 83.9- 100.0%, biomass estimation), characteristically gibel carp. Besides fish, amphibians, crayfish and water beetles were eaten in low proportions, therefore the trophic niche was very narrow in all areas. Otters preyed primarily (>56%) on small-sized (<100g) fish, but at three areas, the consumption ratio of 100-500 g fish was also considerable. The main fish prey was eurytopic (>69%), but stagnophilic or reophilic fishes were also eaten considerably on some areas. Consumption of fish in high proportions indicates that their availability might be satisfactory for otters. However fish surveys ocassionally indicated low fish densities. Diet composition and feeding habits of otters differed between areas. It draws attention to the possible need for different conservation and management objectives of the sensitive valley flat-habitats of the Danube, an important European ecological corridor.