Grasshopper species composition differs between prairie dog colonies and undisturbed sites in a sagebrush grassland

Authors: PEARSE, IAN - Us Geological Survey (USGS); DUCHARDT, COURTNEY - University Of Wyoming; LEGG, LILLIAN - Colorad0 State University; Porensky, Lauren

Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Grasshoppers and prairie dogs both consume a substantial amount of plant biomass in grassland ecosystems, so it is important to understand how these two important groups of herbivores interact. We conducted a landscape-scale survey of grasshopper abundance and community composition in Thunder Basin, Wyoming. We sampled in areas with and without prairie dog colonies. We found no evidence that prairie dogs decrease the total biomass of grasshoppers. Indeed, grasshopper biomass tended to be slightly higher at locations more central within prairie dog colonies. However, some groups of grasshoppers were associated with prairie dog colonies, while other groups were associated with sites off prairie dog colonies. Thus, prairie dogs caused substantial shifts in grasshopper community type. Our results are consistent with a range of past studies in other places that have shown little consistency in prairie dog impacts on grasshopper biomass, but consistent impacts of prairie dogs on grasshopper communities.

Technical Abstract: Grasshoppers are a major consumer of plant biomass in grassland and shrubland ecosystems. While often considered generalists, grasshopper species have differing habitat preferences and interactions with other consumers in grasslands. There are conflicting accounts of how prairie dog colonies and differences in vegetation impact grasshopper abundance and composition. We conducted a landscape-scale survey of grasshopper communities, plant communities, and prairie dogs in a grassland / shrubland ecosystem in eastern Wyoming. Over the eastern Wyoming landscape, spurthroat grasshoppers were associated with lower sagebrush cover and lower cover of C3 grasses, bandwing grasshoppers were associated with low-lying areas with a high cover of C4 grasses and a low cover of cheatgrass, and slantface grasshoppers were associated with low vegetation height. Prairie dogs, because of their effects on vegetation, had different impacts on different groups of grasshoppers. Spurthroat grasshoppers, the Wyoming toothpick grasshopper (Parapomala wyomingensis), and grasshoppers with early-season phenology were associated with prairie dog colonies. However, because some species of grasshoppers were positively and others negatively associated with prairie dogs, the net effect of prairie dogs on grasshopper biomass was neutral. Thus, to determine the role of grasshoppers in prairie ecosystems, it will be important to determine whether there is functional equivalence of grasshopper species in consuming plant biomass and as food for vertebrates.