THE DYNAMIC NATURE OF FORAGE PREFERENCE AND MICROHISTOLOGICAL ATLAS

Moose, Alces alces, are among the most iconic species in the northern circumpolar temperate forests. Multiple factors influence moose density. Winter is a time of severe dietary stress for moose because deciduous trees are leafless and available forage is limited to conifers with high plant secondary metabolites or low-energy deciduous twigs. Forage preference depends on the intrinsic forage properties, abundance of forage and environmental stressors. These stressors include predation risk and severity of climate that affect forage efficiency. We examined forage preference of moose on Isle Royale National Park during winter over a ten-year period. Diet was divided into two categories, coniferous and deciduous. Preference varied relative to abundance of coniferous and deciduous, winter severity and predation risk. As forage abundance increased, coniferous preference decreased. Preference for coniferous forage was weaker during severe winters and predation weakens the negative frequency dependence. Analysis was facilitated with microhistology Microhistological analysis is typically conducted at commercial laboratories and few individuals are trained in this discipline. Furthermore, each forage study entails collection and analysis of reference specimens representative of forage available. This results in additional costs for the research that could be alleviated if published documents were available outlining the characteristics and providing a dichotomous key for the identification of these forage items. Two microhistological atlases, with dichotomous keys, are presented. One covers elk forage of the Greater Yellowstone Ecosystem and the second covers a range of woody plant material across North America. We hope that these atlases will act as a springboard for additional publications extending the microhistological database of available material to addition plant material, not only in North America but in other regions as well