Vegetation structure and composition determine snowshoe hare (Lepus americanus) activity at arctic tree line

摘要

Snowshoe hares (Lepus americanus Erxleben, 1777) are keystone herbivores supporting many boreal-forest predators. Understanding habitat use of hares can help predict how hares and their predators will be affected by disturbances such as climate change, which will have a particularly strong effect at tree line. We examined hare activity at arctic tree line near Churchill, Manitoba, using fecal pellet transects established in August 2012. We counted all hare fecal pellets at two plots per transect andmeasured plant abundance and vegetation structure surrounding the plots, then used model selection to determine the combinations of habitat features or plant species that best explained hare activity or presence. Hare pellets occurred at a higher densitywhere tall shrub cover was high. Pellet density also increased with increasing canopy cover, tree size, tree density, visibility, and small shrub cover, but was negatively correlated with medium-sized shrub and herb cover. Hares preferred areas with willow (genus Salix L.) and avoided areas with unpalatable black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.). With climate warming, tree line is expected to advance northward and the increased tall shrub and willow cover predicted with increasing temperatures should benefit hares by providing greater predator protection and food.