Science and conservation for the world’s 2800 small mammal species

Rodents: Family Castoridae

holding_imgThe family Castoridae includes all modern beavers and their fossil relatives. There is only one genus, Castor, and two species within this genus. These two species are Castor fiber, the European beaver and Castor canadensis, the North American Beaver. The geologic record of this family extends back to the Oligocene, with Castoroides and Palaeocastor being well known extinct members. Members of Castoridae occupy the northern temperate zone, where they serve an important ecological role. They often fell trees due to their feeding on bark and leaves, and their preferences for certain tree types have an impact on the tree species composition in the surrounding area. The building of dams, digging of canals and borrows also modifies the streams and lakes that they occupy. The resulting flooding creates habitats for various different species of wildlife.

Castorids live in small family groups, and mark specific territories with scent mounds. When frightened, they loudly slap the water with their tails as a warning to their family and as a method of startling any potential predator. They are semiaquatic, and use a pelage of long guard hairs and dense underfur for insulation. This coat has made them a target for fur trappers in the past. To aid with their locomotion in water they have a flattened tail and webbed hind feet. Their eyes are protected by nictating membrane, and their nostrils and ears can be closed as well. An interesting characteristic of castorids is that their epiglottis lies above the soft palate in the narial passage. This allows air to flow through without actually entering the mouth cavity. The back of the tongue can rise up to fit against the palate to block the passage of water from the mouth. This characteristic allows castorids to open their mouth underwater to gnaw or carry branches.



Work Cited
Myers, P. 2000. “Castoridae” (On-line), Animal Diversity Web. Accessed October 20, 2014 at

Author: Lauren Naylor