Wild bulls, including species like bison, gaur, and various wild cattle, are large herbivores. They consume a diet composed almost entirely of plant matter, and their foraging activities shape the landscapes they inhabit. Understanding their diet provides insight into their biology and the balance of wild habitats.
Key Dietary Components
Wild bulls predominantly eat grasses. American bison, for example, consume grasses and sedges, which can make up 79–96% of their diet. Wild gaur feed mainly on grass, but also incorporate leaves, forbs, and coarse grasses. Forbs, broad-leafed herbaceous plants like clovers and asters, are a regular part of their consumption, often making up a significant portion later in the growing season.
Beyond grasses and forbs, wild bulls also browse, consuming twigs, leaves, and young shoots from woody plants. Gaur, for instance, browse on leaves from shrubs and may eat bark and fruit from trees like teak and cashew. Water is another dietary component, with bison requiring daily access to water or snow.
Environmental Influences on Foraging
The diet of wild bulls changes based on season and habitat. During lush periods like spring and summer, diverse, high-quality forage is abundant. In winter, when food resources are scarce, these animals switch to lean season forage, including dried grasses, bark, and woody vegetation. This seasonal shift aids survival in temperate climates.
Different habitats also dictate available food. Bison thrive in prairies and plains, where grasses are plentiful. Conversely, gaur are found in evergreen, semi-evergreen, and moist deciduous forests, where their diet includes bamboo, shrubs, and trees. The availability of water sources also influences foraging patterns, as animals tend to graze near water.
Ruminant Digestion and Nutrient Extraction
Wild bulls are ruminants, possessing a specialized digestive system that allows them to extract nutrients from fibrous plant material. This system includes a four-chambered stomach: the rumen, reticulum, omasum, and abomasum. The rumen, the largest compartment, acts as a fermentation vat where plant material is initially stored and exposed to a dense population of symbiotic microorganisms.
These microbes, including bacteria, fungi, and protozoa, produce enzymes like cellulase that break down cellulose, a complex carbohydrate, into simpler sugars and volatile fatty acids. Partially digested food, known as cud, is regurgitated and re-chewed to further break down plant fibers and mix with saliva. This process, called rumination, enhances digestion efficiency.
The cud then passes through the reticulum and into the omasum, where water and some nutrients are absorbed. The abomasum, which functions similarly to a human stomach, completes digestion with gastric juices and enzymes. This system enables wild bulls to thrive on a diet rich in cellulose, which other animals cannot efficiently digest.