Scale-dependent environmental variables affecting red squirrel (Sciurus vulgaris meridionalis) distribution

Abstract

We investigated the effects of habitat fragmentation on the endemic subspecies of red squirrel Sciurus vulgaris meridionalis in the Pollino National Park, Calabria, Southern Italy. Presence/absence of squirrels was monitored using drey (nest) counts in 511-ha census plots. Squirrel dreys were found in 16 plots (31%). Patch size was not correlated to squirrel presence. Squirrels were found in patches ranging from 3.19 to 6051 ha. Small-scale forest structure significantly affected the probability of occurrence. The proportion of conifers and average tree height positively predict squirrel presence; furthermore, nest density was positively correlated with high tree species diversity and the proportion of deciduous oaks (Quercus cerris, Q. ilex). Also at the home-range scale the proportion of conifer forest and oak-dominated deciduous forests positively predicted squirrel presence (200-300m radius). At the even larger scale, corresponding with potential dispersal distances (3000m radius), landscape parameters indicating a lower degree of fragmentation and proportion of oak seemed to favour squirrel presence. Our results emphasize that multi-scale analyses can enhance our understanding of red squirrel distribution, and that their distribution and abundance were mainly determined by forest structure components, such as food availability, at the home-range scale. We underline the importance of protection, and eventually increasing conifer and deciduous oak woods range in the Pollino National Park for the management and conservation of endemic Calabrian red squirrels. © 2010 Unione Zoologica Italiana.