Beavers are aquatic rodents known for their engineering prowess, constructing impressive dams and lodges. Their landscape modifications create diverse ecosystems and provide shelter.
Beavers and Hibernation: The Truth
Beavers do not hibernate, unlike many mammals that enter a deep state of inactivity during winter. True hibernation involves a significant metabolic slowdown, including reduced body temperature, heart rate, and breathing. Beavers do not undergo such physiological changes, nor do they enter torpor. Instead, beavers remain active throughout colder months, though their pace of life slows considerably.
Beavers spend the winter within their lodges, utilizing stored resources. Their activity levels are lower compared to warmer seasons, as they conserve energy and rely on their prepared food supplies.
Active Winter Survival
Beavers possess several physiological adaptations that allow them to remain active even in frigid conditions. Their thick fur coat is a primary defense against the cold, consisting of two layers: a dense underfur that traps air for insulation and longer, oily guard hairs that provide waterproofing. Beavers diligently groom themselves, spreading oil from glands to maintain their fur’s waterproofing, minimizing heat loss in water.
Their bodies are well-suited for aquatic life, allowing extended underwater periods. Beavers can hold their breath for 15 to 20 minutes, benefiting navigation under ice or avoiding predators. While their core body temperature remains stable, their abdominal temperature can drop during cold water immersion, and they tolerate some peripheral cooling in extremities like their tails and feet. Beavers also exhibit a countercurrent exchange system in their limbs, where arteries and veins are wrapped around each other, regulating heat exchange and preventing extremities from freezing.
Winter Food Storage and Shelter
Before winter arrives, beavers engage in extensive preparations. Their lodges, built from sticks, logs, and aquatic vegetation, are coated with mud that freezes like cement, providing robust insulation and protection from predators. These dome-shaped structures feature underwater entrances, offering security from land-based threats and remaining accessible even when the pond surface freezes over. The lodge’s interior chamber is located above water level, staying warmer than the outside air due to its thick walls and the body heat of the beaver family inside.
A crucial preparation is the creation of substantial underwater food caches. Beavers submerge branches and saplings near their lodge entrances, anchoring them into the mud. This submerged storage helps preserve the food and allows beavers to access it throughout winter without needing to venture onto frozen land. Their winter diet primarily consists of the inner bark, or cambium, of woody plants, with preferred species including aspen, willow, birch, maple, alder, and cottonwood. A colony’s food cache can weigh between 1,500 to 2,500 pounds, providing enough sustenance for the entire family until spring.