Modeling the Influence of Forest Structure on Microsite Habitat Use by Snowshoe Hares

Angela K Fuller,Daniel J Harrison

doi:10.1155/2013/892327

Abstract

Snowshoe hare (Lepus americanus) is an important prey species for many Carnivora and has strong influences on community structure and function in northern forests. An understanding of within-stand (microsite) forest structural characteristics that promote high use by hares is important to provide forest management guidelines. We measured forest structural characteristics at the microsite-scale in north-central Maine and used an information-theoretic modeling approach to infer which characteristics were most strongly associated with use by hares during winter. We measured overwinter hare pellet density to model relationships among microsite-scale vegetation structure and hare use. Overwinter pellet density was positively associated with live stem cover (3 × coniferous saplings + deciduous saplings) and negatively associated with overstory canopy closure; the two variables explained 71% of the variation in microsite use by hares. The highest pellet densities were in grids with canopy closure <72% and stem cover units >22,000 stems/ha. Silvicultural practices that create dense areas of conifer and deciduous saplings should receive high within-stand use by hares in winter. These conditions can be achieved by promoting the release of advanced regeneration and reducing overstory cover to encourage establishment of shade-intolerant species; clearcutting is one such silvicultural prescription to achieve these conditions.

Highlights

Snowshoe hare (Lepus americanus) have been reported to strongly influence community structure and function in northern boreal forests [1] and is an important prey species for many Carnivora including coyotes (Canis latrans) [2,3,4], fisher (Martes pennanti) [5, 6], American marten (Martes americana) [7,8,9], bobcat (Lynx rufus) [3], red fox [3, 10], and Canada lynx (Lynx canadensis) [11, 12]
The lynx is a specialist on snowshoe hares [11, 12], and habitat use by lynx is closely associated with density of hares [4, 14,15,16,17,18]
Average canopy cover among the 25 microsite grids sampled was 65.56% (SE = 6.05), basal area averaged 20.71 m2/ha (SE = 2.98), stem cover units averaged 14,376/ha (SE = 2,406), and understory lateral foliage density averaged 55.95% (SE = 4.52)

Summary

Introduction

Snowshoe hare (Lepus americanus) have been reported to strongly influence community structure and function in northern boreal forests [1] and is an important prey species for many Carnivora including coyotes (Canis latrans) [2,3,4], fisher (Martes pennanti) [5, 6], American marten (Martes americana) [7,8,9], bobcat (Lynx rufus) [3], red fox [3, 10], and Canada lynx (Lynx canadensis) [11, 12]. The lynx is a specialist on snowshoe hares [11, 12], and habitat use by lynx is closely associated with density of hares [4, 14,15,16,17,18]. Survival of snowshoe hares may be lower in forest stands with little understory cover [2, 19, 20], and overall survival depends on stand-specific hare density, presence of predators, and the hunting success of predators [21]. Hares exposed to terrestrial predation during a cyclic low in the population did not use more protected habitats and did not modify their foraging behavior to reduce the risk of predation [23], suggesting that behavioral plasticity of hares may be limited (i.e., they may select for dense understory structure across a range of hare and predator densities)

Methods

Results

Conclusion