Castoridae

Castoridae is a family of semi-aquatic rodents commonly known as beavers. The group includes the living genus Castor, with two extant species: Castor canadensis (North American beaver) and Castor fiber (Eurasian beaver). Beavers are renowned for their dam-building behavior, which creates wetlands that support diverse ecosystems. They have large, orange incisors that grow continuously and are used for gnawing wood, strong jaws, a broad flat tail that functions as a rudder and for balance, and hind feet that are webbed for swimming.

Beyond living species, the castorids have a rich fossil record. Extinct genera include Castoroides, the giant beaver of North America during the Pleistocene; Steneofiber from the Miocene to Pliocene; and Palaeocastor from the Oligocene to Miocene. Some early castorids reached substantial sizes and occupied similar ecological roles to modern beavers, often shaping landscapes through dam-building and tree-felling.

They are herbivores, feeding on bark, cambium, twigs, and aquatic vegetation. They typically construct lodges or burrows near water and build dams that raise water levels, slow flow, and create ponds. These activities make them ecological engineers, increasing habitat complexity and benefiting many other species while influencing local hydrology.

Conservation and human interaction: Beavers have been valued for their fur and castoreum, and have historically suffered from overhunting and habitat loss. Recent conservation measures have helped populations recover in many regions. The ecological impact of beavers—dams, lodges, and resulting wetlands—continues to be a focus of habitat management and ecosystem restoration efforts.