Grazing by wild and domestic ungulates reduces floral resources and native bee abundance in a multi-use landscape
| Authors: | Will Glenny, Sandra J. DeBano, Mary M. Rowland, Scott R. Mitchell, Skyler Burrows, Michael Wisdom, Joshua P. Averett, Bridgett Naylor |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Pacific Northwest Research Station |
| DOI: | https://doi.org/10.1016/j.biocon.2026.111952 |
| Source: | Biological Conservation |
Abstract
The breadth of management goals in large and complex landscapes encompasses biotic communities with diverse life histories. However, managing multiple communities may be challenging when resource requirements overlap, like forage for ungulates and floral resources for bees. For three years in a riparian forest in northeastern Oregon, USA, we manipulated the presence of wild deer and elk, domestic cattle, and the combination of wild and domestic ungulates, to understand the separate and cumulative influence of grazing by different functional feeding guilds on bloom and bee communities. While we found no effect of individual grazing treatments, of either wild or domestic ungulates on bloom and bee abundance or richness, there was a negative association between cumulative herbivore pressure of all ungulates and bloom and bee abundance. Additionally, bloom community composition differed by grazing treatment late in the growing season, primarily because several blooming species were annuals associated with cattle grazing. Using information on elk dietary preferences and bee-flower associations, we found that elk-preferred forbs are attractive to bees and occupy important positions in mutualist networks. Bees that specialize on these forbs may be at risk of decline if co-occurring elk selectively reduce floral resources. Management strategies, such as electronic fences, phenologically informed livestock grazing, targeted seed mixes, increased physical complexity in riparian areas, and/or improved ungulate forage allocation, could help maintain ecosystem services provided by ungulates, while preserving floral-rich habitats for bees.