Test of the prey-base hypothesis to explain use of red squirrel midden sites by American martens

We tested the prey-base hypothesis to determine whether selection of red sq uirrel (Tamiasciurus hudsonicus) midden sites (cone caches) by American mar tens (Martes americana) for resting and denning could be attributed to grea ter abundance of small-mammal prey. Five years of livetrapping at 180 sampl ing stations in 2 drainages showed that small mammals, particularly red-bac ked voles (Clethrionomys gapperi) and shrews (Sorex spp.), were more abunda nt at midden sites than at non-midden sites. However, logistic regression i ndicated that middens occurred in spruce-fir (Picea engelmannii - Abies las iocarpa) stands, being correlated with decreasing lodgepole pine (Pinus con torta) basal area, decreasing distance to water, and increasing canopy cove r. Since middens were not randomly distributed, we constructed multiple lin ear regression models to determine the variability in small-mammal abundanc e and species richness attributable to structural and landscape variables. Regression models indicated that abundance of small mammals, red-backed vol es, and uncommon small mammals could be predicted from structural and lands cape variables, but midden presence did not significantly improve these mod els. Midden presence was a significant but weak predictor of small-mammal s pecies richness. Our data do not support the prey-base hypothesis for expla ining martens' selection of resting and denning sites near red squirrel mid dens at the scales we tested.