Beavers are known for their ability to fell trees. This raises questions about their diet and the reasons behind their tree-cutting behavior. Understanding these aspects reveals their complex relationship with the environment.
Beaver Diet: What They Consume
Beavers are herbivores. While known for felling trees, they do not consume the hard, woody core. Their diet primarily consists of the inner bark, or cambium layer, which is rich in sugars and nutrients. They also eat leaves, twigs, and buds from trees and shrubs.
Beavers prefer certain tree species, favoring those with softer wood and palatable inner bark. Aspen, willow, and cottonwood are top choices due to their soft wood and accessible bark. Other preferred deciduous trees include birch, maple, and alder. In addition to woody materials, beavers consume soft vegetation, especially during warmer months, including aquatic plants like water lilies and cattails, grasses, sedges, and other herbaceous plants.
Beyond Food: Why Beavers Fell Trees
Felling trees serves multiple purposes for beavers. Their engineering skills allow them to transform landscapes, creating habitats that offer protection and resource access. They primarily use cut trees and branches for constructing dams, building lodges, and caching food for the winter. This strategic use of wood highlights their adaptability and resourcefulness.
Beavers construct dams to create ponds that provide a safe, deep-water refuge from predators like coyotes, wolves, and bears. These dams, built from trees, branches, mud, and rocks, raise water levels, providing easier access to food and materials, as beavers are more agile in water than on land. They can even dig canals to float heavy loads of wood to their construction sites.
Within these ponds, beavers build their homes, called lodges. These dome-shaped structures are constructed from branches, logs, and aquatic vegetation, cemented together with mud. Lodges typically have underwater entrances, providing a secure living space. The thick walls of mud and wood freeze into a solid, insulated shelter, offering protection from harsh weather conditions.
Another reason for felling trees is to create a winter food cache. As autumn approaches, beavers cut down branches and submerge them near their lodge, anchoring them in the muddy bottom of the pond. This underwater stockpile remains accessible even when the pond freezes over, ensuring a steady food supply of inner bark, twigs, and buds.
Ecological Impact of Beaver Activities
Beaver activities have widespread effects on the environment, shaping ecosystems and providing numerous benefits. Their dam-building creates new wetlands and expands existing riparian habitats, which are areas along rivers and streams. These wetlands increase biodiversity, offering diverse habitats for plants and animals.
Beaver ponds support various organisms, including fish, amphibians, insects, and birds, by providing food, shelter, and breeding grounds. Studies show beaver-created wetlands can have higher diversity of aquatic plants and insects compared to other wetlands. Beavers also improve water quality. Their dams slow water flow, allowing sediments and pollutants to settle, acting as natural filtration systems. This process can reduce nitrates, phosphates, carbon, and silicates in the water.
Beaver dams also influence water flow and landscape hydrology. They increase groundwater tables by storing runoff, helping maintain water availability during dry periods. By slowing water flow, dams reduce the peak impact of floods and minimize erosion downstream. These actions contribute to more stable water regimes, benefiting both aquatic and terrestrial ecosystems.