Smallest Herbivores Create the Biggest Impact for Grassland Forage

by Smithsonian’s National Zoo & Conservation Biology Institute
September 10, 2025

Soil nutrients support plants, and the animals who consume plants return these nutrients to the soil, creating a nutrient cycle. In a new study published in Ecology, scientists from the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) found that in prairie grasslands, the smallest herbivores—namely prairie dogs and grasshoppers—increase rates of nutrient cycling to a greater degree than larger herbivores such as bison and cattle. 

Grasslands cover 25–40% of the land on Earth and provide many benefits to the environment, including sequestering carbon, controlling erosion and hosting a diversity of life. Yet grasslands are some of the most threated terrestrial ecosystems, and herbivores, which play critical roles in nutrient cycling in grassland ecosystems, face many conservation challenges. In North America, bison and prairie dogs likely number only 1–2% of the populations of animals that roamed the Great Plains prior to European arrival. In the interest of identifying how these herbivores shape grassland ecosystems, researchers examined the contributions of prairie dogs, grasshoppers, bison and cattle on grass and soil nutrition across 15 shortgrass prairie sites in northeast Montana, an area of active research representing a collage of conservation, ranching and agricultural landscapes.  

“Herbivores contribute to the green food web by turning plant tissues into urine and dung that provide new plant growth with readily available nutrients,” said Ellen Welti, NZCBI community ecologist and the study’s senior author. “This cycles nutrients at a faster rate than the brown food web, where plant tissues slowly senesce and degrade before nutrients become available for uptake by future plants.” 

Keep reading: https://nationalzoo.si.edu/news/smallest-herbivores-create-biggest-impact-grassland-forage

Read the Ecology paper: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.70192