Big Bluestem (Andropogon gerardii) stands as a prominent native grass across North American prairies. Known as the “monarch of the prairie,” this tall perennial can reach heights of up to 8 feet, displaying a distinctive purplish-blue hue at its stem base. Its unique three-parted seed heads, often compared to a turkey’s foot, are a memorable sight in the landscape. Historically, Big Bluestem formed a significant component of the vast tallgrass prairies, playing a foundational role in these ecosystems.
Primary Grazers
Large mammalian herbivores historically and currently consume Big Bluestem, a grass known for its high palatability and nutritional value, especially in its younger stages. American Bison, once abundant across the Great Plains, grazed extensively on this grass, shaping prairie landscapes through their movements and feeding patterns. Elk also forage on Big Bluestem, contributing to the historical grazing pressure that influenced prairie health. This grass maintains a high crude protein content, ranging from 16-18% from May through August, making it an appealing food source.
Domestic livestock, particularly cattle, readily consume Big Bluestem, especially during spring and summer when its new growth is most palatable. It is considered a high-quality forage species for all classes of livestock. Ranchers often refer to it as “ice-cream grass” due to its preferred status among grazing animals. While Big Bluestem can withstand considerable grazing, continuous consumption closer than 6 to 8 inches can allow other grass species to outcompete it. Proper management, such as rotational grazing, helps maintain the health and vigor of Big Bluestem pastures for livestock.
Smaller Herbivores and Invertebrates
Beyond large grazers, a variety of smaller animals and insects also feed on Big Bluestem, utilizing different parts of the plant. White-tailed deer graze on the grass, particularly its early, green stages of growth. Rabbits are natural grazers, and Big Bluestem forms a part of their diet in prairie regions, offering high fiber content beneficial for their digestion. Rodents such as voles and mice also consume the foliage of Big Bluestem.
Numerous insect species interact with Big Bluestem, often as a food source for their larval stages. Grasshoppers eat the leaves of the grass. Caterpillars of various skipper butterflies feed on the foliage. Leafhoppers also feed on Big Bluestem.
Ecological Significance of Consumption
The consumption of Big Bluestem by various herbivores plays an important role in maintaining the health and diversity of prairie ecosystems. Grazing influences nutrient cycling, as consumed plant material is returned to the soil through waste, enriching it with nitrogen and phosphorus. Herbivory can also affect plant growth patterns; moderate grazing can stimulate new growth and improve forage quality. However, frequent, intensive defoliation can reduce root mass and limit the plant’s ability to recover.
Herbivores can prevent dominant species like Big Bluestem from outcompeting other plants, thereby increasing overall plant diversity within the ecosystem. Their feeding patterns can create openings and reduce the biomass of fast-growing grasses, allowing smaller, slower-growing plant species to establish. Additionally, the movement of grazing animals can aid in seed dispersal, contributing to the spread of Big Bluestem and other prairie plants across the landscape. The continuous interaction between Big Bluestem and its consumers is integral to the dynamic balance and resilience of prairie environments.