Dieta de la nutria Lutra lutra (Linnaeus, 1758) en la cuenca del alto Ebro, norte de España

Resumen

Diet of the Otter Lutra lutra (Linnaeus, 1758) in the upper reaches of the River Ebro catchment,northern Spain
Food habits of Otters were studied through the analysis of 367 faeces collected from 1974 to 1979. Fish and crustaceans represent 90% of the total occurrences. The most common species in the faeces was the Crayfish (Austropotamobius pallipes), followed by several fishes (P. phoxinus, Salmo trutta, Chondrostoma toxostoma, Barbus bocagei, etc). Pyrenean Desman (Galemys pyrenaicus) remains were found in 1.4% of the samples. Crayfish were most frequently ‘eaten in summer (when they are most active) and fish in winter (when their swimming speed is lower). Trophic diversity was higher in summer. Prey weighing from 15 to 35 g were consumed more often. Otters seem to be opportunistic hunters, vulnerability playing a more important role than abundance when deciding what to eat.