Water is important for the North American beaver (Castor Canadensis). Most beaver live in burrows in the bank of a stream, lake or pond with the actual living quarters above the waterline. Some beaver live in lodges, usually constructed in the water or on the bank of a stream, lake or pond, again with the living quarters above the water level. Whether a lodge or burrow, beaver enter their home through underwater entrances. Bodies of water that are deep enough to provide an entrance under the water do not need to be dammed. Beaver build dams only where the water level is not deep enough throughout the year. A beaver dam only maintains deep water and is not a beaver’s home. A lodge or burrow in or on the bank of the pond created by the beaver dam is where the beaver lives. A beaver lodge is built from tree branches, mud, twigs, and rocks.
The location of a beaver lodge or burrow depends on the depth, width and gradient of the stream or body of water. Beaver prefer streams with a low gradient and slower water flow. Food availability is critical in choosing a lodge site. Beaver prefer to live near successional trees such as aspen, willow or cottonwood rather than mature forests. Protection from ice, wind and waves are also considerations in selecting a home site.
The underwater entrances (usually two) provide safety. In areas where the winters are harsh, beaver stockpile (“muddy down”) green twigs and sticks in the bottom of the water near their lodge or burrow to be eaten when the water is frozen over.
Along Ash Creek in Ash Creek Wildlife Area (Modoc and Lassen Counties CA) are several beaver lodges. The one easily accessible to us is constructed from a variety of materials including 2 x 4s. The picture of Leonard standing by the lodge shows its proportions. There are no nearby trees of any size. Out of curiosity we once took some green cottonwood trimmings from our yard and laid them along the bank of the creek about 100 yards from the pictured lodge. The next day every one of the branches we laid out was gone. We assume the beaver ate or cached the branches. In winter and early spring the beaver lodge is easily visible, but vegetation camouflages it in the summer.
The final two pictures are of the entrance to a beaver burrow at Baum Lake (Shasta County CA). The cloudy water marks the access to the underground entrance. Alders are plentiful near this spot and many beaver-gnawed tree stumps and branches litter the area.
More about the North American beaver in my next post.