Food resources and diet composition in riparian and upland habitats for Sitka Mice, Peromyscus keeni sitkensis

Abstract

Food resources and diet composition of Sitka Mice, Peromyscus keeni sitkensis, were studied over a four-year period in four floodplain and upland forest habitats: old-growth Sitka Spruce (Picea sitchensis) floodplain; Red Alder (Alnus rubra) floodplain; Beaver (Castor canadensis)-pond floodplain; and nearby old-growth Sitka Spruce-Western Hemlock (Tsuga heterophylla) upland forest. Food resources in each habitat were quantified in terms of understory biomass and species richness, fruit production, tree seedfall, and relative abundance of arthropods. Diet composition was analyzed from stomach contents. Between-year differences in the availability of food resources were substantial, but between-habitat differences were minor. Diet composition differed between years and between months within years but did not differ between habitat types or age and sex classes of mice. We conclude that floodplain habitats do not provide unique food resources for Sitka Mice in comparison to upland old-growth forests. However, spatial and temporal complexity within habitats is an important feature of habitat quality in floodplain forests for Peromyscus mice.