Beavers are often recognized as nature’s engineers, known for their remarkable ability to fell trees and manipulate wood in their environment. Their interaction with wood often leads to the common assumption that beavers consume it as a primary food source. While their activities undeniably involve wood, the reasons behind their felling and gnawing behaviors are more complex than simple dietary needs. Understanding these nuances clarifies how beavers utilize wood for various aspects of their survival and habitat modification.
The Purpose of Gnawing Wood
Beavers primarily gnaw on wood not for nutritional value, but as a critical activity for their dental health. Their large, orange-enameled incisors grow continuously throughout their lives, a unique adaptation among rodents. Without constant wear, these teeth would grow too long, eventually making it impossible for the beaver to eat or even close its mouth. Gnawing on tough woody material helps to abrade the teeth, keeping them at a functional length and maintaining sharp, chisel-like edges.
The act of gnawing is a mechanical necessity, preventing the overgrowth that could lead to severe health issues or starvation. As beavers chew, the softer dentin on the inside of their incisors wears away faster than the harder enamel on the outside. This differential wear creates a sharp, self-sharpening edge that allows them to efficiently cut down trees and branches. The act of gnawing also helps to remove the outer bark layer, making the inner, more nutritious cambium layer accessible for consumption.
What Beavers Really Eat
While beavers process a significant amount of wood, their actual diet consists of softer plant materials, distinguishing them as strict herbivores. They primarily consume the inner bark, known as the cambium layer, which is a nutrient-rich tissue found directly beneath the outer bark of trees. This layer is much more digestible than the tough, fibrous woody core of a tree. Their preferred tree species for this purpose include aspen, willow, and birch, which offer palatable inner bark.
Beyond tree bark, beavers also forage extensively on leaves, twigs, and buds from various deciduous trees and shrubs. During warmer months, their diet expands to include a wide array of aquatic vegetation, such as water lilies, cattails, and sedges. They also consume roots, rhizomes, and other herbaceous plants found near their watery habitats. These diverse plant materials provide the necessary nutrients and energy for their robust metabolic needs.
Building with Wood for Survival
Beavers extend their use of wood beyond gnawing and selective consumption, employing it extensively for engineering their environment and ensuring their survival. They are renowned for constructing dams, which are intricate structures built from branches, logs, mud, and rocks. These dams impound water, creating ponds that serve as their primary habitat, offering protection from predators and regulating water levels. The deep, still water created by these dams allows for underwater access to their lodges and food sources, even during winter months when surfaces freeze.
Within these ponds, beavers construct lodges, their secure shelters, typically built from interwoven branches, mud, and plant material. These lodges feature underwater entrances, providing a barrier against predators such as coyotes, wolves, and bears. The thick walls of the lodge also offer insulation, protecting the beavers from harsh weather conditions and providing a safe place to raise their young. Furthermore, beavers create food caches near their lodges, piling branches and small logs into the water to store an accessible food supply for winter when other vegetation is scarce.