Snowshoe Hares (Lepus americanus) in the Western United States: Movement in a Dynamic Managed Landscape

Abstract

Abstract Since the listing of the Canada lynx, Lynx canadensis, as threatened in the coterminous United States (U.S. Fish and Wildlife Service 2000), the effect of landscape-scale forest management on populations of snowshoe hares, Lepus americanus, has been a concern. Snowshoe hares are the central prey species of lynx (Aubry et al. 2000). Because snowshoe hare densities vary widely across different types of forested vegetation structure (Adams 1959, Dolbeer and Clark 1975, Wolff 1980, Wolfe et al. 1982), changes in forest vegetation structure through natural disturbance, succession, and silviculture can have dramatic impacts on populations. Snowshoe hare populations cycle with a regular 9-to 11-year period in the northern portion of the species range (Keith 1990), but evidence of a cycle to the south is mixed (Hodges 2000). Vegetative succession complicates population models (Johnson 2000). In western Montana, we have found highest snowshoe hare densities in regenerating forest stands with high sapling density and in uncut, late-seral-stage forest stands also with abundant saplings. This high-quality snow-shoe hare habitat in Montana can be thought of as having a bimodal distribution relative to forest stand age, with only young and much older stands providing the “closed” understories with abundant cover and browse (Buskirk et al. 2000). The layer of abundant shrubs and saplings that regenerates following clearcuts or large fires later disappears as the lower limbs die on growing trees, but this layer may reappear when large trees die, creating canopy gaps (Oliver and Larson 1986). The potentially long period when the stand understory becomes and remains comparatively “open” is a time of lower habitat quality. Anthropogenic canopy gaps in partially harvested stands can also stimulate growth of a dense understory layer under an established canopy (DeBell et al. 1997, Tappeiner et al. 1997).