Small mammal population and habitat responses to forest thinning and prescribed fire

Abstract

We examined changes in small mammal habitat and densities of four small mammal species, including deer mice (Peromyscus maniculatus), gray-collared chipmunks (Tamias cinereicollis), golden-mantled ground squirrels (Spermophilus lateralis), and Mexican woodrats (Neotoma mexicana), 2–3 years after thinning and prescribed fire treatments in ponderosa pine (Pinus ponderosa) forests of northern Arizona, US. These treatments were designed to simultaneously reduce high-severity fire risk while returning forests to conditions more representative of pre-European settlement structure and function. Treatments resulted in changes in important components of small mammal habitat, including increased herbaceous vegetation, decreased shrub density, and decreased woody debris. Deer mouse densities were negatively related to tree densities. Gray-collared chipmunks were negatively affected by treatment, negatively related to tree density, and positively related to woody debris. Golden-mantled ground squirrels did not appear to vary strongly with either treatment or treatment-related habitat changes, but appeared to be somewhat positively related to shrub cover. Mexican woodrats were positively related to shrub cover, and were positively, but weakly, related to woody debris. Overall, forest thinning can be expected to increase densities of small mammals in these forests, and retention of slash in fuel reduction/restoration treatments may further increase small mammal densities in the post-treatment community. However, reduction of shrubs and woody debris with overly frequent prescribed fire entries may reduce small mammal densities.