Nature Note: Beavers’ Winter Cabins

Beavers (Castor canadensis) are similar to many humans when it comes to weathering winter: they don’t hibernate, but they spend a lot of their time cozied up in their lodges.   

Ever the industrious species, North America’s largest rodent will spend most of the autumn season preparing their winter residence. In early fall, after the framework of a dam has been established, a beaver family will transition their ongoing work schedule to constructing their lodge. Read on for more on the schematics of a beaver lodge and beaver activity in the winter and early spring: 

The site for this structure is typically in a shallow section of water as far from the shore as possible—shallow water prevents flooding into the lodge, but distance from the shore provides extra protection from terrestrial predators. Beaver lodges are impressively constructed: mounds of sticks packed with mud jutting above the water’s surface, sealed with insulating mud and small air holes for ventilation, and an underwater passageway to enter and exit. 

Typically, five to six beavers will reside in the lodge during winter, including two parents, one to three yearlings, and one to three kits born earlier in the year. This group helps generate body heat, keeping the lodge much warmer than the outside air. For example, one lodge studied in Ontario maintained a temperature of 32°F while the outside temperatures ranged from 19°F to -6°F. 

Beavers store their food supply in underwater caches. Protected by ice, the cache is like a refrigerator. A winter meal will typically go like this: the beaver leaves the dark lodge through the underwater passageway, swims through the equally dark waters, grabs some twigs from the food cache, returns to the lodge to eat the twigs like corn-on-the-cob, and then swims back out to discard any scraps before going back to sleep. This process repeats for months.  

With no clear distinction between day and night, beavers no longer follow a 24-hour cycle. Instead, they shift to a 26-28 hour rhythm, with some individuals having cycles longer than 29 hours, allowing the beaver to sleep more, rest, and conserve energy. 

Come springtime, beaver families usually waste little time vacating their lodges in pursuit of a new site. While cabin fever may play a role here, studies indicate that the main driver of this is rising water levels with spring thaws and resource depletion in the surrounding woods. The lodge is abandoned and may never be used again, which is why you may see several lodges in the same pond or riverbank.