Observations on plant choice by foraging Yellow-Bellied Marmots

Abstract

Yellow-bellied Marmots (Marmota flaviventris) are generalist herbivores that feed on a wide variety of grasses and forbs. Food items are not used in proportion to their abundance in the environment and some parts of plants are preferred over other parts. Plant species composition differs among marmot habitats and seasonally. Thus, marmots must adjust plant choice based on availability. For example, at one site marmots in late summer forage extensively on fruits of gooseberries (Ribes) and elderberry (Sambucus), which are not present at other sites. Marmots selectively forage on flowers of tall plants (Lupinus, Aquilegia, Delphinium) and seed heads of grasses by standing, grasping the plant with the forefeet, and bending the flower or seed head to the mouth. Other plant species are treated similarly, but rejected after they are placed into the mouth or touched to the lips (Linum, Aster, Helianthella, Castillea). Plants not utilized by marmots may grow abundantly around marmot burrows (Happlopappus, Epilobium). Some widespread species growing in meadows where marmots forage are not eaten (Veratrum, Frasera). Early in the spring when food resources are low, marmots feed on the spring beauty (Claytonia) but not glacier lilies (Erythronium). Similarly, in late summer when many plant species are senescent and food resources are declining, marmots do not use many abundant species, such as various composites and gentians. Selection of particular species such as elderberry may increase foraging time but with low feeding time. Food choice may in part be determined by experiences as well as palatability and availability.