Castor canadensis (American Beaver) typically construct lodges out of tree trunks, branches, and mud, or dig dens into banks at the edges of water bodies. We observed Beavers in a Mississippi swamp using a hollow Taxodium distichum (Baldcypress) snag as a lodge. In 2016, they had constructed a mound inside of the snag and were observed sitting out of the water inside of the snag. In subsequent years, they continued to use the snag and, in autumn of 2020, constructed a more traditional lodge against it. After being disturbed, Beavers took refuge in another nearby hollow snag on 2 occasions. Beavers are adaptable, occasionally using unusual materials to construct lodges or dams or occupying non-traditional structures, but we found no previous account of them residing inside of a standing hollow tree.
Adams, Susan B.; Gelbard, Elaine M. 2021. American Beavers (Castor canadensis) use a hollow Baldcypress snag as a lodge. Southeastern Naturalist. 20(1):N22-N29. https://doi.org/10.1656/058.020.0116.