Investigating the Scale of Diet Selection for Sage-grouse: The Effects of Patch and Bite Sizes on Foraging

Document Type

Student Presentation

Presentation Date

April 2016

Faculty Sponsor

Jennifer Forbey


Foraging herbivores must meet nutritional requirements not only by finding enough plant biomass to consume, but also finding plants with high protein and low concentrations of potentially toxic plant secondary metabolites (PSMs). Greater Sage-grouse (Centrocercus urophasianus) are sagebrush obligate herbivores that consume relatively high concentrations of PSMs. In Idaho, sage-grouse selected a species of sagebrush that had lower concentrations of monoterpenes over a more abundant species with higher concentration of monoterpenes. Diet selection by sage-grouse may be driven by chemical and nutritional traits at several scales, including at the individual plant (morphotype) and leaf level. Our research aims to understand how diet selection is influenced by the chemical and nutritional quality of plant morphotypes within a foraging patch and whether sage-grouse select specific morphotypes of sagebrush to maximize nutrition consumed per bite or minimize toxin consumed per bite. For each sagebrush morphotype we determined the density and volume. We then measured leaf biomass and monoterpene concentration. Our results showed that browsing is not proportional to biomass availability or nutritional quality, but that sage-grouse selected sagebrush morphotypes to minimize PSM intake. This research is important to understand how sage-grouse select and use habitats at different spatial scales.

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