Diet Overlap of Mammalian Herbivores and Native Bees: Implications for Managing Co-occurring Grazers and Pollinators

Many federal, state, and tribal agencies, as well as nonprofit organizations, have recently increased efforts to understand how natural areas can be managed to enhance native pollinators and the ecosystem services they provide. However, managing this important group must be balanced with other services that natural areas provide including hunting, timber production, and livestock grazing. Significant knowledge gaps exist about how to effectively manage habitats used by large ungulates (e.g., cattle (Bos taurus), elk (Cervus elaphus), mule deer (Odocoileus hemionus)) in ways that also enhance pollinators. One key gap is understanding the degree to which diets of mammalian herbivores overlap with floral resources used by bees, and how this overlap varies spatially and temporally. Invertebrate pollinators, including bees, rely on flowering forbs and shrubs for nectar and pollen. Ungulates also feed on flowering plants, although preferences vary by ungulate species, vegetation community, and season. Here we review existing literature on ungulate diets relative to flowering plants and compare this information with flower preferences of bees, drawing on studies of bee abundance and diversity at the Starkey Experimental Forest and Range in northeastern Oregon. Our review can inform managers about the potential dietary overlap between ungulates and native bees and aid planning efforts aimed at biodiversity conservation of pollinators. We discuss management implications relative to seasonal habitat use and dietary preferences of ungulates and variation in bee phenology, and conclude with guidance about timing and intensity of ungulate grazing when managing for multiple conservation objectives, especially in sensitive habitats like riparian areas.