Beavers are large, semi-aquatic rodents known for their dam-building and engineering capabilities. Their close relationship with wood often leads to questions about their diet. Beavers are strict herbivores, meaning their diet consists entirely of plant matter. They have no nutritional requirement for consuming meat, fish, or insects, which distinguishes them from many other waterfront animals.
Yes, Beavers Are Strict Herbivores
Beavers are classified as monogastric herbivores, relying exclusively on vegetation for their sustenance. This dietary classification means they avoid all animal protein, a significant detail often misunderstood because of their habit of felling trees. While beavers use wood extensively for constructing their lodges and dams, the tough, structural wood itself is not a primary food source. They obtain their nutrients from specific parts of the trees and other flora found in and around their aquatic habitats. The purpose of gnawing down a tree is usually to access the softer branches and leaves or to use the trunk as building material. Even when they consume parts of a tree, they are targeting the specific plant tissues, not the dense wood.
Seasonal Variety in the Beaver Diet
The beaver diet changes significantly with the seasons, adapting to the availability of different types of vegetation. During the warmer months of spring and summer, beavers primarily consume soft, herbaceous plants. They forage on a wide variety of aquatic vegetation like water lilies, pondweed, and cattails, which are easily digestible and plentiful. On land, their summer menu includes grasses, forbs, roots, and rhizomes near the water’s edge. This soft-tissue diet requires less energy to process and provides necessary nutrients.
As the weather cools, their dietary focus shifts to the more energy-dense food necessary for winter survival. The winter diet centers on the bark and tender twigs of woody plants, which they must store in advance. Beavers prefer the inner bark, known as the cambium layer, of deciduous trees such as aspen, willow, cottonwood, and birch. This cambium is rich in carbohydrates and sugars, providing a concentrated energy source. To prepare for winter, they create large underwater food caches near their lodge entrance, allowing them to access these woody branches even when the water surface is frozen solid.
Specialized Digestive System for Processing Cellulose
To survive on a high-fiber diet of bark and woody material, beavers possess a highly specialized digestive system. They are classified as hindgut fermenters, a characteristic that allows them to break down cellulose, the tough polymer that forms plant cell walls. This digestion occurs primarily in an enlarged organ called the cecum, located between the small and large intestines.
The beaver’s cecum functions as a fermentation vat, housing specialized bacteria and microorganisms. These microbes produce the enzymes necessary to break down cellulose, converting the indigestible fiber into usable volatile fatty acids and other nutrients. This process is necessary for extracting sufficient energy from their plant-based diet.
To maximize nutrient absorption from this high-cellulose food, beavers engage in coprophagy, or the re-ingestion of their own feces. They produce soft fecal pellets, rich in microbial proteins and B vitamins synthesized in the cecum, which they consume directly. Running the nutrient-rich material through the digestive system a second time ensures they gain the maximum benefit from the tough plant matter they eat.