Downed wood removal effects on survival and site fidelity of woodrats in a California oak woodland

Abstract

Owing to the increasing intensity and frequency of wildfires in the western United States, the removal of woody debris (downed dead wood and snags) from fire-prone landscapes is being evaluated for wildfire mitigation. Consequently, the study of the ecological value of coarse woody debris to sustain dependent species has become of foremost importance. From 2004–2009, we used a before-after control-impact (BACI) study design to assess the effects of downed wood removal on a population of big-eared woodrats (Neotoma macrotis) in an oak woodland (Quercus spp.) in coastal-central California, USA. Using Pollock's robust design mark-recapture analyses (with 12 primary capture occasions represented by trapping each spring and fall, and secondary occasions composed of 3 trap nights), we estimated survival and emigration rates. Further, applying mixed-effects models, we evaluated the effects of 7 habitat attributes on woodrat abundance and reproduction. Following the experimental removal of downed wood from the 11 randomly selected treatment plots, woodrat survival was higher (P = 0.013), and emigration was lower (P = 0.007) among 11 control plots on which downed wood was retained. Woodrat abundance within plots was best predicted by stem density, demonstrating positive demographic associations with habitat complexity. Plot-level reproductive success (i.e., the presence of juveniles within a plot during spring) was more likely with increasing snag density. These findings indicate that snags and downed dead wood are key components of high-quality habitat for big-eared woodrats. Management of woody debris to mitigate wildfire risk should consider the ecological value of this habitat attribute for big-eared woodrats and other dependent species.