Trophic structure and habitat determinants of a Mediterranean carnivore guild: insights from the Sierra de la Culebra (NW Spain)

The aim of this study was to understand how mesocarnivores are structured as a function of habitat type and in the presence of a top predator such as the wolf. Indeed, the Sierra de la Culebra (Zamora, NW Spain) hosts one of the densest populations of Iberian wolves ( Canis lupus signatus ) in Western Europe, together with a diverse guild of mesocarnivores. We investigated habitat determinants of carnivore diversity and trophic structure using a non-invasive, multi-method approach that combined camera trapping, faecal DNA identification, and interviews with local rangers across twelve 7.5 × 7.5 km grid cells (65,000 ha). Seven camera trap stations were positioned in the grid, with one camera trap per station, after the results were cross-referenced with 253 fecal samples and a survey conducted among Park staff. Finally, to determine the habitat, the relative abundance index (RAI) for each taxon was calculated using the formula suggested by Lira-Torres and Briones Salas. Twelve carnivore species were recorded, with wolves and red foxes ubiquitous and smaller mustelids showing patchy distributions although wolf presence exerted a weak negative influence on mesocarnivore richness, suggesting moderate top-down regulation within the guild. As regards the characterization of the habitat multiple regression models revealed that deciduous forests and shrublands were positively associated with total species richness, while pine plantations and croplands had negative effects therefore the carnivore community of the Sierra de la Culebra has shown a significant predilection for forest areas with deciduous or thicket forests, strongly reaching coniferous forests (generally repopulation) and cultivated areas. In the European context, where the wolf is a sensitive species, these results demonstrate that carnivore diversity in Mediterranean landscapes depends on both trophic and habitat complexity. Ecological restoration in the Sierra de la Culebra should therefore prioritize the recovery of native oak woodlands and mixed shrub mosaics to maintain a functionally rich and balanced predator community.