Análisis de la alimentación y distribución del visón americano (Neovison vison) y de la nutria (Lutra lutra) en la población simpátrica del río Moros (Sistema Central, Segovia)

Abstract

The distribution of the American mink (Neovison vison) has been continuous in the last decades in the river Moros basin (Segovia) and in its tributary streams and reservoirs at all altitudes , while the otter distribution (Lutra lutra) is linked to the river Moros, mainly to the middle course, alter the recolonization which began less than two decades ago and with a seasonal presence in the high altitude stretches of the river. The trophic ecology was studied by the analysis of 321 feces (spraints) (130 of otters and 191 of mink) collected during 13 months in 5 study sites located 64 in the high and middle stretches of the river, including 2 small mountain dams and a large dam in the middle stretch with a great human presence. Fish are the fundamental prey of the otters throughout the year and at all altitudes, the rest prey are accidentals. Mammals and fish are the fundamental prey for the American mink. The diversity of the otter’s diet is considerably smaller than that of the mink in all the stretches of the river. The overlap of the diets between otters and minks throughout the study is over 83%. Considering the sites in sympatry for both species is greater than 89%. The distribution of otters in the river Moros seems to be stable in the last samplings. The American mink distribution did not become reduced in the area and it is present in all the same river courses in which it was detected more than 25 years ago. Trapping minks has been insufficient to control this alien carnivore, which seems to tolerate the presence of otters in seasonal sympatry avoiding competition for trophic resources and shelters.