FORAGE BY SUBARCTIC BROWSING VERTEBRATES: The Role of Plant Chemistry

Plant palatability frequently moderates vertebrate herbivore forage selec­ tion patterns (e.g. 72, 73, 103, 104, 111, 137, 179,195). There is, however, considerable debate as to which plant chemical characteristics control pala­ tability (e.g. 9, 42, 110, 118, 120, 216). On the one hand, forage proximal nutritional quality is believed to be of primary importance (e.g. 18, 51, 103, 114, 130, 133, 137, 161, 173, 215). On the other, there is increasing specula­ tion that forage selection patterns are largely the result of avoidance of plant secondary constituents that are antagonistic to vertebrate herbivore fitness (e.g. 1, 2, 9, 12, 25, 49, 112, 116, 120, 141, 153, 165, 199,200). In this paper we examine these alternatives for a specific system. We consider the interface between subarctic browsing vertebrates and woody browse plants during winter and attempt to answer the following questions: During winter do subarctic browsing vertebrates (a) feed prefer­ entially upon plant tissues that contain relatively high concentrations of proximal nutrients or energy, or (b) consistently avoid plant tissues that