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Summer diet selection by snowshoe hares Seccombe-Hett, Pippa Elizabeth

Abstract

The primary objective of this study was to identify the plant species included in the diets of male snowshoe hares (Lepus americanus) during the summer months. Snowshoe hare selection for and against each plant species was assessed by comparing the relative use and availability of each plant species. The secondary objective was to examine several hypotheses of what influenced the selection of those species individually and within an integrated modeling framework. Three hypotheses were examined, i) Hares might select plants with high nutritional content (of energy or protein), ii) Hares might select plants to avoid or minimize deleterious plant secondary compounds (i.e. tannins and alkaloids), iii) Hares might select plants that minimize their risk of predation. The hare diet during the summer consists of five main plant species: Betula glandulosa, Festuca altaica, Lupinus arcticus, Salix spp. and Shepherdia canadensis, although a number of other species were occasionally included. Nutritionally, hares select for plant species with high protein content and avoid toxic effects from secondary compounds by ingesting a diverse diet. Hares are not consistently found associated with any particular vegetation types, although they prefer habitats with both a dense understory and an abundance of preferred food species. Although some support was generated for all of the hypotheses of diet selection, no single hypothesis explained all of the observed patterns of diet selection. A linear programming foraging model combined with optimization techniques was thus used to examine the interactions between the variables. Overall, the model is successful in integrating the conflicting hypotheses of hare foraging. It appears that hares change their diet selection response to conflicting goals such as reproductive condition and risk of predation. The model suggests that the interaction between plant protein and chemical defense compounds are the primary determinants of hare diet.

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