Spatial distribution models in a frugivorous carnivore, the stone marten (Martes foina): is the fleshy-fruit availability a useful predictor?

Abstract

Fleshy-fruit availability is rarely used as a predictor in stone marten (Martes foina) habitat models, despite its frugivorous carnivore diet. Data on stone marten occurrence, habitat structure and fleshy-fruit species abundance was collected along 2 km long survey routes within 2 × 2 km sample plots (n = 30). Two different spatial scales were considered: 1) the entire survey route; and 2) 200 m segments within each 2 km survey route. Data analyses included Poisson General Linear Models (GLM) and Generalized Linear Mixed Models (GLMM) for the first and second approaches, respectively.Strawberry tree (Arbutus unedo) availability was significantly and positively correlated to stone marten occurrence at both spatial scales, particularly for the large-scale model. At the larger scale, a lower correlation to the traditional habitat structure variables was observed. Tree cover was the most important variable in the small-scale model, but strawberry tree availability was also an important predictor. Stone marten abundance was low in areas of high tree cover and absence of strawberry trees; emphasising the prominent role of strawberry trees per se in the abundance of stone martens. Our results indicated that including fine, field-derived estimates of key food resources for species can increase the utility of habitat models.