Forest Disturbance and the Long Term Population Persistence of the Mt. Graham Red Squirrel: A Spatially Explicit Modeling Approach

Abstract

We combined field data with high-resolution satellite imagery and a spatially explicit population model to predict long-term population dynamics of the endangered Mt. Graham red squirrel (MGRS: Tamiasciurus hudsonicus grahamensis), with the goal of examining effects of disturbance on MGRS population dynamics. We found that modeling MGRS dynamics improved with population specific data. Our results indicate that predation and competition potentially have large, adverse effects on population abundance. Habitat quality analysis indicates much of the spruce-fir forest is degraded to the point that it cannot support MGRS, therefore, the future of the species will rely on management in the mixed conifer zones. Our models predict that future populations will not show the variability exhibited in abundance over the past 20 years, likely due to degradation of spruce-fir forests, and that even low levels of fire and insect disturbance have the potential to drive MGRS population below critical population thresholds.