Abundance and ecological associations of small mammals

Effective conservation and management of small mammals require knowledge of the population dynamics of co-occurring species. We estimated the abundances, autocorrelations, and spatiotemporal associations of 4 small-mammal species from 2011?2016 using live-trapping mark-recapture methods on 9 sites across elevation and canopy openness gradients of a late-successional forest in the H. J. Andrews Experimental Forest, on the west slope of the Oregon Cascades. We also quantified species-specific spatial variation in adult sex ratios and body mass. We used Huggins closed capture models to estimate site- and year-specific abundances of 4 target species: Humboldt's flying squirrels (Glaucomys oregonensis), Townsend's chipmunks (Neotamias townsendii), western red-backed voles (Myodes californicus), and deer mice (Peromyscus maniculatus). We estimated the temporal autocorrelations among site- and species-specific abundance estimates and used generalized linear mixed effects models to investigate the effects of 7 spatiotemporal covariates on species-specific mean abundance estimates. Species-specific adult sex ratios, juvenile to adult ratios, and adult body masses were not widely variable among study sites. Abundance estimates varied by as much as 4-fold among years and 6-fold among sites. Humboldt's flying squirrel abundance was temporally autocorrelated at intervals of 1 and 5 years, Townsend's chipmunk abundance was temporally autocorrelated at intervals of 1?4 years, and western red-backed vole abundance was temporally autocorrelated at 1, 4, and 5 years. Mean fall abundance estimates were associated with elevation and climate and in some cases, canopy openness and berry-producing shrubs, but the direction of the association differed among species for some covariates. Our findings could provide additional management tools for small-mammal abundance objectives, and highlight the importance of careful covariate selection in studies using indices of small-mammal abundance.
Keywords: Cascade Mountains, deer mice (Peromyscus maniculatus), habitat, Humboldt's flying squirrels (Glaucomys oregonensis), mark-recapture, Oregon, population cycle, Townsend's chipmunks (Neotamias townsendii), western red-backed voles (Myodes californicus)