Here's why:
* Diet: Bisons primarily eat grasses, sedges, and other plants. They have specialized digestive systems that are designed to break down tough plant matter.
* Teeth: Their teeth are adapted for grinding vegetation, not tearing flesh.
* Lack of predatory adaptations: They lack the sharp claws, fangs, and hunting instincts of carnivores.
While they might occasionally consume a small amount of insect life, their diet is overwhelmingly plant-based, making them herbivores.