Anàlisi de la dieta i rang de distribució de la llúdriga (Lutra lutra) a la zona lacustre de l’estany de Banyoles

Abstract

The aim of this project is study the otter (Lutra lutra) population of the lake System of Banyoles, which is not well known. To understand this population dynamics, the activity pattern, diet, distribution and habitat use of the otter were examined. A total of 59 otter spraints were collected, 93 sites were recorded across the habitat and 25 sites were monitored using remote cameras. The diet composition of otters in the study zone was investigated by spraint analysis between summers of 2006, 2008 and 2017, and also with the results obtained by Clavero et al., 2003 in Mediterranean freshwater habitats, using the percentage frequency of occurrence. Overall, American crayfish (Procambarus clarkii) represented the dominant food, followed by fish and amphibians. The actual food composition of otters differed significantly from 2006 and 2008 composition and those from Mediterranean freshwater habitats, increasing the consumption of crayfish and becoming the main food resource in the summer period. In addition, Shannon trophic diversity index was calculated and demonstrated a narrow niche breadth. The distribution and habitat use map was carried out form data of the 93 recorded sites, and we located two focuses of the otter activity. Significant correlations were recorded between otter activity and vegetation cover, road and city proximity. The activity pattern was calculated from captures of the camera traps, deployed in riparian habitat along streams and lakeshore. We found that otter population of the study area haven’t modified their activity pattern from otters of the Iberian Peninsula. From the results, it follows that a conservation plan for the study zone should suggest an improvement of the riparian habitat in those sections that could be used as corridors for the movement of the individuals connecting the different populations (or subpopulations), like the channels and the Canaleta brook. Likewise, it’s important to undertake actions like the recovery and conservation of the natural space of Can Morgat forest, which is the centre of otter population activity