Beavers are well-known for felling trees, but the common assumption that they eat the hard, woody parts is a misconception. As herbivores, their interaction with trees serves purposes beyond consumption, highlighting their unique diet and ecological role.
Beavers’ Primary Diet
Beavers are herbivores. Their food choices vary significantly with the seasons. In spring and summer, they predominantly eat soft vegetation, including aquatic plants like water lilies, cattails, sedges, and rushes. They also consume leaves, buds, and tender twigs of various trees and shrubs during these warmer months.
As fall approaches, and especially during winter when fresh herbaceous growth is scarce, their diet shifts to more woody components. This includes the inner bark, known as cambium, and twigs from deciduous trees such as willow, cottonwood, aspen, poplar, maple, birch, and alder. Beavers store these woody materials underwater near their lodges to ensure a food supply when ice covers their ponds.
Why Beavers Cut Down Trees
Beavers fell trees for several reasons, not for eating the hard wood. A primary motivation is to gather materials for constructing and maintaining their dams and lodges. Dams create ponds that provide a protective moat around their homes, offering safety from predators such as wolves and bears. Lodges, built from branches, mud, and rocks, offer a secure living space with underwater entrances, ensuring protection from the elements and predators.
Felling trees also allows beavers to access more palatable parts of the tree that would otherwise be out of reach. They are particularly interested in the tender twigs and the nutritious inner bark, or cambium, found higher up in the tree. By bringing down a tree, they can strip these desirable parts for consumption. This behavior also contributes to creating an environment conducive to the growth of preferred food plants by opening up the forest canopy.
Is Wood Truly Part of Their Diet?
Their diet focuses on the softer, more nutritious components. The part of the tree they do consume is primarily the inner bark, or cambium layer, a thin, nutrient-rich tissue located just beneath the outer bark. This cambium is rich in carbohydrates and serves as an important food source, particularly during colder months when other vegetation is unavailable.
While beavers process plant material, their digestive system, like that of many herbivores, is adapted to break down cellulose. They possess an enlarged cecum, a pouch in their digestive tract that contains microorganisms. These microbes help ferment and digest cellulose from the plant materials they consume, allowing them to extract nutrients. However, this digestive capability does not extend to efficiently breaking down the lignin and dense cellulose found in the hard wood of tree trunks.