The definitive answer to whether bison prey on elk is no. Both the American bison (Bison bison) and the elk (Cervus canadensis) are North America’s largest terrestrial herbivores and are classified as ungulates. They share expansive habitats and are both primary consumers, meaning their diet is entirely plant-based. The idea of one preying on the other is biologically impossible, as neither species possesses the anatomical or digestive systems required for a carnivorous diet.
The Bison Diet: Specialized Grazers
The American bison is a specialized grazer, or graminivore, meaning its diet is overwhelmingly dominated by grasses and grass-like plants such as sedges. Their physical structure, including a broad muzzle and a low-slung head, is well-suited for cropping vegetation close to the ground. This feeding strategy is distinct from the browsing behavior of many other ungulates.
Bison are ruminants, possessing a four-chambered stomach that allows for the digestion of tough, high-fiber forage. This digestive system requires the food to be regurgitated and re-chewed as cud, a process that breaks down the cellulose-rich plant material. The long retention time of forage in their digestive tract, which can be around 80 hours, allows the massive volume of grasses to be fully processed.
This digestive specialization means bison can thrive on lower-quality forage than many other herbivores, such as cattle. While they may occasionally incorporate forbs, sagebrush, or woody vegetation into their diet when grasses are scarce, their entire physiology is adapted for a life sustained by fibrous plants. The bison lacks any adaptations for hunting or consuming meat.
The Elk Diet and True Predators
Elk, in contrast to bison, are mixed feeders, meaning they both graze on grasses and browse on woody shrubs and forbs. Their diet is more flexible and shifts significantly depending on the season and the availability of nutrient-rich plants. During the summer, their diet is dominated by grasses and forbs, but in winter, they increase their consumption of woody browse to survive.
The nutritional demands of elk are highest in the summer to support gestation, lactation, and growth, making the quality of their forage important. They actively seek out the most nutritious grasses and forbs available, often leading to a wide-ranging foraging pattern. This variation in feeding habits allows them to exploit a wider range of habitats than the more restricted bison.
The animals that actually prey on elk are true carnivores, such as wolves, mountain lions, and bears. The threat of these predators significantly influences elk behavior, causing them to alter their diet and habitat use for security. For example, elk may retreat from open grasslands into treelines, shifting from grazing to browsing, to avoid areas where they are vulnerable to attack.
Competition for Resources and Behavioral Interactions
When bison and elk share the same range, their interaction is primarily one of competition for resources, not predator and prey. Both species rely heavily on grasses, and this overlap in dietary needs can lead to direct competition for the best forage, especially in shared winter habitats. This ecological relationship is a classic example of interspecific competition among herbivores.
Bison are generally the dominant animal in these shared environments due to their significantly larger size and immense physical power. They will often displace elk from desirable grazing areas or water sources. Observed aggressive behaviors, such as a bison chasing or butting an elk, are usually acts of territoriality or dominance, not an attempt to hunt or consume the smaller animal.
These antagonistic interactions are occasionally observed when a bison encounters a weak or downed elk, which they may butt or mob. However, this is interpreted as a hyper-aggressive or defensive display rather than predatory intent. Any observed aggression stems from resource disputes or social dominance hierarchies, fundamentally different from a predator-prey dynamic.