Patch selection by wintering white-tailed deer : consequences for eastern hemlock regeneration at local and landscape scales

Anthropogenic changes in landscape composition or configuration have the potential to increase the abundance of generalist species, often resulting in cascading effects on other trophic levels and ecosystem function. The selection or utilization of individual patches of habitat, however, may vary in both time and space, as a result of patch and landscape attributes as well as dynamic abiotic factors, such as snowfall. Given that scale-specific habitat decisions are often an indication of the risk-reward trade-offs to fitness, we hypothesized that the use of high-quality habitat would be most strongly influenced by snow at local scales and by composition and the configuration of the landscape at greater spatial scales. To test this, we examined white-tailed deer (Odocoileus virginianus) selection of eastern hemlock (Tsuga canadensis) patches as winter habitat. Within-patch habitat structure and patch use were monitored for three consecutive years. The surrounding landscape was characterized using existing spatial data sets. Patch level attributes were poor predictors of patch use in areas with strong gradients in abiotic factors relevant to the energetics of movement or forage acquisition. Additionally, heterogeneity in the greater landscape served to increase use and homogeneity deterred use, suggesting that risk-reward trade-offs may be the greatest at 1 This chapter has been submitted as a manuscript for publication by Witt, JC , Webster, CR, Drummer, TD, Froese, RE, Vucetich, JA, and Peterson, RO and is currently in review at The Journal of Wildlife Management. 15 the coarsest spatial scales (3000 m radius buffer). Decisions regarding habitat modification meant to mitigate the damaging effects of an overabundant species should incorporate knowledge of coarse-scale factors that serve to limit, or encourage, habitat use. Introduction Human-influenced changes in landscape composition and configuration have led to locally overabundant or expanding distributions of native generalist species that are able to exploit these conditions (Garrott and White, 1993; Anderson, 1997). For some of these species, expanding populations have, in turn, led to local changes in or simplification of food webs, decreases in diversity, and homogenization of habitat (Garrott and White, 1993). For example, increasing fragmentation or patchiness in the sawgrass (Cladium jamaicense) ecosystem of the Florida Everglades has led, in part, to an increase in probability of conversion from sawgrass to a cattail (Typha spp.) monoculture, a species that has a strong influence over water chemistry and cascading effects in the Everglades food chain (Wu et al., 1997). Tallmon et al. (2003) demonstrated that white-footed mouse (Peromyscus leucopus) densities were higher in fragmented versus unfragmented forests, and the increase in seed predation had the potential to lead to reduced recruitment or local extinctions of Pacific trillium (Trillium ovatum). Landscapes with a high interspersion of forested and agricultural lands have also been shown to have a positive influence on the density and diversity of avian predator species, leading to an increase in nest predation and declines in songbird