Efectos del hábitat y la disponibilidad de presas sobre la dieta y la distribución de la nutria (Lutra lutra) en el Parque Natural Sierra Norte de Sevilla

Abstract

The otter is widespread through all the Parque Natural Sierra Norte de Sevilla and surrounding areas. We found that the otter varied its intensity of use of habitat in the course of the portion of the longitudinal gradient defined as headwaters-middle reaches. The otter tended to use more intensively middle reaches instead of headwaters, related to food sources availability. The otter fed on 20 different preys: 11 different freshwater fish species (The Iberian barbell, calandino, the sun fish, the Iberian sandsmelt, the Iberian chub, the Iberian nase, pardilla and common trout), seven vertebrates no fishes (common frogs, common toads, urodels, water snakes, birds y micromamifers) and two invertebrates (the red swamp crayfish and insects). Within all these preys the Iberian barbell (Barbus sclateri), the red swamp crayfish (Procambarus clarkii) and common frog (Rana perezi) stood out in this order of preference. 61% of preys and 84% of total biomass corresponded to freshwater fish individuals. This fact underlines the high importance that freshwater fishes had for the otters' diet within the study area. However, otter’s diet showed a faithfully pattern in relation to preys availability, since they mainly fed on the most available preys. This general pattern must be specified, as the otter tended to select or reject some fi sh species and/or fish sizes. Long sized fishes were specially consumed except for the sun fish (Lepomis gibbosus) with which this general pattern appeared inverted. In summary we can say that the Sierra Norte's otter population is in good or very good health.