Causes and consequences of the postfire increase in deer mouse (Peromyscus maniculatus) abundance

Wildfire triggers an increase in deer mouse (Peromyscus maniculatus) abundance. Here, I describe this phenomenon, investigate its causes, and explore the consequences of the postfire increase in mice for conifer recruitment in burned forest. I documented a shift in small mammal communities away from more specialized species such as red-backed voles (Myodes gapperi) and shrews (Sorex spp.) and towards greater abundance of generalist deer mice after a wildfire in montane forest. I conducted a meta-analysis of published studies on the abundance of small mammals in disturbed versus undisturbed forests and established that the pattern of increased deer mouse abundance holds for both natural (wildfire) and anthropogenic (different forms of forest harvest) disturbances. However, the postfire increase is significantly stronger than the increase after logging. In another forest wildfire, I tested the four most commonly proposed explanations of this increase: (1) greater abundance of food resources in burned areas, (2) increased foraging efficiency of deer mice, (3), predatory release, and (4) source - sink dynamics, with burned areas acting as high abundance dispersal sink. However, none were supported by data. Thus, I concluded that the existing explanations of postfire increase in deer mouse abundance are unsatisfactory. Finally, I investigated the magnitude and impact of seed predation by deer mice in burned and unburned forest. In seed offerings experiments, overnight conifer seed removal associated with deer mice was more intense in burned than in unburned stands. In germination experiments, emergence of seedlings in cages with openings that allowed access by deer mice was extremely rare in burned and unburned forest. However, in closed cages (deer mice excluded), seedling emergence was low in unburned forest, but considerably higher in burned forest. Wildfire created favorable conditions for seedling recruitment but seed predation by deer mice appeared to remove this advantage.