Is Diet Selection by Greater Sage-Grouse Influenced by Biomass Availability or Toxins?

Forging herbivores must meet nutritional requirements by finding plant biomass to consume and finding plants with high protein and low toxin concentration. Greater Sage-grouse ( Centrocercus urophasianus ) selected a species of sagebrush that had lower concentrations of monoterpenes within a habitat over a more abundant species with few toxins. Diet selection may be driven by smaller spatial scales once a species of plant is selected. Our research aims to determine how diet selection is influenced by availability of food and whether sage-grouse select specific morphotypes of sagebrush to maximize biomass consumed per bite or minimize toxin consumed per bite. At each patch, we identified sage-grouse foraging site using tracks and fresh pellets. For each sagebrush morphotype we determined density and volume. We then measured biomass and monoterpene concentration of the leaves. Our results showed that browsing is not proportional to biomass availability, but that sage-grouse selected sagebrush morphotypes to minimize toxin intake. This research is important to understand plant-herbivore interactions and to know how sage-grouse select and use habitats at different spatial scales.