Demographic responses of small mammal populations to a herbicide application in coastal coniferous forest: population density and resiliency
This study was designed to assess the demographic responses of small mammal populations to herbicide-induced habitat alteration in a 7-year-old Douglas-fir plantation near Maple Ridge, British Columbia, Canada. Populations of the deer mouse (Peromyscus maniculatus), Oregon vole (Microtus oregoni), Townsend chipmunk (Eutamias townsendii), and shrews (Sorex spp.) were sampled in control and treatment habitats from April 1981 to September 1983 and from April to October 1985. Recolonization of removal areas by these species was also monitored in both habitats. There was little difference in abundance of deer mice, Oregon voles, and shrews between control and treatment study areas. Chipmunk populations appeared to decline temporarily on the treatment areas relative to controls. Recolonization by voles was not affected by habitat change, but for deer mice was lower on the treatment than control area. Both deer mouse and Oregon vole populations were at comparable densities on control and treatment areas in the second and fourth years after herbicide treatment. The proportion of breeding animals and average duration of life were similar in control and treatment populations of deer mice and voles. These small mammal species should be able to persist in areas of coastal coniferous forest that are treated with herbicide for conifer release.