A bison is not a carnivore. These large mammals are classified as herbivores, meaning their diet consists almost entirely of plant matter. This article examines the scientific basis for this classification by looking at dietary groups, the specific plants bison consume, and the unique biological adaptations that allow them to process such a fibrous diet.
Understanding Dietary Classifications
The scientific classification of an animal’s diet falls into three primary categories based on its main food source. A carnivore, which literally means “meat-eater,” subsists on the flesh of other animals and possesses digestive systems adapted for processing animal protein. In contrast, an herbivore is an animal whose diet is exclusively or almost entirely plant-based, requiring a specialized digestive tract to break down tough cellulose. The third category, an omnivore, is a dietary generalist that consumes a varied diet including both plant and animal matter.
The Bison’s Primary Food Sources
The American bison is scientifically categorized as a grazer, primarily consuming plants found in grasslands and meadows. Grasses and sedges constitute over 90% of a bison’s food intake by volume throughout the year. Specific prairie species, such as Blue gramma and little bluestem, form the bulk of their energy source. They will also consume forbs (broad-leaf flowering plants) and occasionally browse on the leaves or twigs of woody plants, especially when grasses are scarce or less nutritious.
Adaptations for Grazing
The ability of a bison to thrive on a diet of tough, fibrous plants is due to its classification as a ruminant. Like cattle, bison possess a multi-chambered stomach, with the largest chamber being the rumen. This stomach acts as a fermentation vat, housing billions of specialized microorganisms, including bacteria and protozoa. These microbes produce enzymes that chemically break down cellulose, a complex carbohydrate that is indigestible to non-ruminants. This process allows the bison to extract nutrients and energy from lower-quality forage.
Dental Structure
Additionally, bison have high-crowned teeth, known as hypsodont molars, which are a physical adaptation designed for continuous grinding. These large, durable teeth help to pulverize the abrasive grasses and sedges that are often coated in soil or silica, preventing the excessive wear that would occur with a less specialized dental structure.