Beaver facts

Facts and myths about beavers

Beavers are large animals, much larger than many people expect. An adult beaver is longer than 1m and weighs over 20kg.

Beavers are entirely herbivorous. In the summer their diet consists of a wide range of plants found in and around the water. In the winter months, when the vegetation is not as lush, they switch their attention to bark and the young shoots of trees. They do not eat fish.

Beavers don’t usually kill trees. Beavers’ preferred foods are willow, aspen, and poplar, which are able to resprout readily in response to beavers cutting them down. In fact, these trees may have evolved this ability to survive the activities of beavers and other large mammals, and today it makes it possible to coppice and lay hedges. Beavers also take a wide range of other broadleaved trees which don’t coppice, such as oak, ash, and beech. Important trees can be protected where desirable. 

Beavers are slow to breed. They have one litter of kits a year, usually born in May. A pair will have an average of three kits per year which usually emerge from the burrow in June or July.

Beaver numbers are controlled by other beavers. While young beavers, particularly kits, can be predated on by red fox, domestic dogs, pine marten, birds of prey, American mink, otters, badgers and even large pike adult numbers are typically regulated by their territorial nature. Beavers often kill each other when their population approaches a level which can’t be supported by the availability of food – the ecological carrying capacity.

Beavers live in burrows and lodges. They need an underwater entrance to feel safe, so if the water is not deep enough they build dams to hold a permanently raised level of water.

Beavers feel safest in water. They generally feed within 10m of the water’s edge, and escape into the water if they feel threatened. They also dig canals to enable easier access to vegetation for food and for building materials for dams and lodges.

Beavers and disease Like all native mammals, beavers can carry a range of pathogens and host-specific parasites. Long-term health monitoring of Scottish beavers has revealed they do not appear to be significant reservoirs of diseases and the risk of introducing significant disease to humans, domestic animals or wildlife from captive bred or wild beavers in Britain was low. Any translocated individuals are screened for a range of pathogens of concern before being released.

Do beavers prevent fish passage The impact beaver dams have on migrating fish is complex, site specific and change over time. In low flows dams can form temporal barriers to fish movement, and in man-made canalised channels fish passage can be limited. During high periods of flow beaver dams can be passable and in naturalised areas where the river is given sufficient buffer from intensive land use it can potentially cut around a dam creating side channels for use by migrating.

Living with beavers

Farmer Chris Jones travels to Bavaria, Germany to meet farmers and local residents living alongside beavers fifty years after they were reintroduced.