Background/Question/Methods      Within forest ecosystems, terrestrial small mammals often use habitat features such as downed woody debris (DWD) and understory shrubs for protective cover. Given the presumed value of these resources, one such species, the red-backed vole (Myotes gapperi), is commonly more abundant in stands with greater amounts of DWD and a denser shrub layer. It is less well understood, however, whether local variations in DWD or shrub layer characteristics alter this species' patterns of habitat use within stands.

Do individuals consistently use those parts of stands in which protective cover is abundant more frequently than localities in which it is sparse? Can the DWD and shrub layer characteristics with which this species is associated be quantified to determine the levels that best satisfy its needs at a microhabitat scale?      We developed models to predict variation from stand-average red-backed vole capture probabilities as functions of the relative localized abundance of DWD, the composition and abundance of understory shrubs, and neighbourhood overstory characteristics. Relationships with local habitat structure were modelled using sigmoidal functional forms to elucidate potential non-linear responses by this species. We estimated parameters using maximum likelihood techniques, and evaluated competing models within an information-theoretic framework.

Results/Conclusions      Red-backed voles were associated with high moisture and low light environments (as represented by ordinations of shrub composition), a high density of short (about 1-2 m height) shrubs, greater amounts of early-decay-class DWD, and a low local basal area of poplar in the overstory. Voles responded most strongly to both DWD and shrub cover in sites where these features were sparse. Downed woody debris appeared to be of lower importance than cover provided by short understory shrubs.      Our results imply that habitat suitability for these species may depend not only on the overall abundance of DWD and understory shrubs, but also on their local spatial distribution and consequent effects on patterns of microhabitat use.