Castor fiberEurasian beaver

Geographic Range

Eurasian beavers, Castor fiber, once heavily populated all of Europe and Asia. However due to overhunting for fur and castoreum, a chemical from their castor sacs, and habitat loss, populations fell nearly to extinction. By the 19th century most countries in Europe and Asia had no remaining beavers. By the 20th century an estimated 1300 beavers remained in the wild. Management efforts and reintroductions have resulted in Eurasian beaver population increases. Populations are now established in France, Germany, Poland, southern Scandinavia, and central Russia. However, populations are small and scattered throughout this area. (Long, 2003; Nolet, 2000)


Eurasian beavers are semi-aquatic and inhabit freshwater systems, including lakes, ponds, rivers, and streams, usually in forested areas but also in marshes and swamps. Permanent access to water is necessary and preferred tree species for C. fiber are willows, aspen, birch, and alder. Beavers prefer slow-moving or still, deep water and will alter habitat if necessary to create these conditions. Water quality is not as important as water access, food availability, and depth of water. (Long, 2003; Middleton, 1999; Nolet, 2000; Nowak, 1999)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Eurasian beavers weigh from 13 to 35 kg and are 73 to 135 cm in length. Eurasian beavers have two layers of fur, the first is a soft dense undercoat that is dark grayish in color. The outer layer is longer, stiff reddish brown hairs called guard hairs. Fur color tends to be darker in northern populations. Eurasian beavers have two castoreum glands located next to the cloacal opening. These glands produce a pungent, sweet smelling chemical called castoreum and is used to mark territories. The muzzle is blunt, ears are small, and the legs are short. Both ears and nostrils are valvular and the eyes have nictitating membranes, closing when they go under water. The tail is naked and black with scales. The tail is broad, oval, and flattened horizontally. The feet are dark brown to black and each have 5 digits. The rear feet are webbed and the inside two toes have a split nail used for grooming. The tail is narrower and the skull smaller than those of North American beavers, Castor canadensis. Inside the mouth, beavers have a skin fold that allows them to gnaw on branches under water without getting water in their mouths. They have two, large incisor teeth with hard, orange-colored enamel on the anterior surface. Sexes are alike, although females may tend to be larger. (Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999; Rue, 2002)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    13 to 35 kg
    28.63 to 77.09 lb
  • Range length
    73 to 135 cm
    28.74 to 53.15 in


Eurasian beavers are monogamous and only one adult pair breeds per colony. Females come into estrus between January and February, but sometimes warm winter weather can result in a breeding season as early as December. Copulation takes place in the water most of the time but, in some cases, takes place in the lodge. The male will approach a female floating in the water from the side, copulation may last anywhere from 30 seconds to 3 minutes. Most copulations occur at night. If a mature female is not impregnated the first time she will come into estrus 2 to 4 times again throughout the season. Family members cooperate to care for the young of the primary pair. (Ducroz, et al., 2005; Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999; Rue, 2002)

Eurasian beavers breed yearly in the spring between January and February. The gestation period is 60 to 128 days and they can have up to 6 or more young, but 1 to 3 is more common. Newborn weight is 230 to 630 g. The young are usually weaned by 6 weeks old. During that time the female takes care of the young, cleaning and feeding them. After the young are weaned, sub-adults in the colony help feed them by bringing small twigs and soft bark to them until they are about 3 months old. At 1.5 to 2 years old young beavers disperse, often being forced out by the adult female. (Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999)

  • Breeding interval
    Eurasian beaver pairs breed once yearly.
  • Breeding season
    Eurasian beavers can breed from January to Febuary.
  • Range number of offspring
    1 to 6
  • Average number of offspring
  • Average number of offspring
  • Range gestation period
    60 to 128 days
  • Average weaning age
    6 weeks
  • Range time to independence
    1.5 to 2 years
  • Range age at sexual or reproductive maturity (female)
    1.5 to 3 years
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Range age at sexual or reproductive maturity (male)
    1.5 to 3 years
  • Average age at sexual or reproductive maturity (male)
    3 years

Eurasian beavers live is small family groups consisting of one breeding adult female and male, young of the year, yearlings, and sub-adults. After young are weaned, sub-adults help with raising the young. The young are skittish outside the lodge and are never far from an adult. After dispersal at 1.5 to 2 years of age they become sub-adults at another colony until they are ready to breed and start their own colony. (Ducroz, et al., 2005; Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999; Rue, 2002)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • extended period of juvenile learning


Eurasian beavers can live 10 to 17 years of age but rarely live longer than 7 to 8 years in the wild. In captivity, some sources suggest that beavers can live up to 35 years and are expected to reach 24 years of age. However, these ages are unconfirmed. A confirmed record of longevity in captivity in Castor fiber was 13.7 years old. (AnAge database, 2009; Ducroz, et al., 2005; Long, 2003; Nolet, 2000; Nowak, 1999)

  • Range lifespan
    Status: wild
    10 to 17 years
  • Range lifespan
    Status: captivity
    13.7 (high) years
  • Typical lifespan
    Status: wild
    7 to 8 years
  • Average lifespan
    Status: captivity
    25.0 years
    Max Planck Institute for Demographic Research


Eurasian beavers are primarily nocturnal, although they may also be active during the day. Their dens are usually burrows in the bank of a river or pond. In locations where the bank is not suitable, they construct lodges away from shore out of sticks and mud. In the lodges, beavers live in colonies of up to 12. These colonies consist of only one dominant, monogamous breeding pair. The dominant female decides when it is time for the young to travel outside the den for the first time and when the young need to disperse. Beavers are semi-aquatic and can stay under water for 4 to 5 minutes at a time. They are active throughout the year, hardly ever coming above the ice surface during the winter months in their northernmost regions. For this reason beavers spend the autumn season building food caches in the water to last them through the winter. Food caches consist of woody vegetation, such as willow and aspen branches. Beavers are a keystone species, having the ability to change the flow and nutrient cycling of a watershed by building dams to regulate water depth. However, Eurasian beavers are more conservative than their North American cousins, usually constructing much smaller dams and lodges. Eurasian beavers are very territorial and mark their territory with castoreum, a form of olfactory communication. They do this by building a scent mound on the shore. They bring mud and vegetation up from the bottom, holding it tight to their chest with their forelegs and pushing themselves up the bank with their hind legs until they have a mound. The beaver will then apply castoreum to the mud pile creating a scent mound. Beavers act very aggressively towards an unknown scent mound in their territory often hissing at it and slapping the water with the tail and resurfacing right away. Most often they will create a scent mound next to it or on top of it. Eurasian beavers must groom themselves constantly to maintain the water repellency of their fur. They use the split toe nails on their rear toes to comb oils from their oil glands into their guard hairs. This makes the outer layer of fur waterproof and the inner layer never gets wet. Without these oils, beavers would become wet to the skin and not be able to spend as much time in the water or withstand cold water temperatures. (Long, 2003; Middleton, 1999; Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999; Rue, 2002)

Home Range

Eurasian beaver home range size varies by available food, watershed size, colony size, and time of year. During the winter months territory size drops to an area that can be patrolled daily with one trip under water, since there is ice cover. During the warm months territory size can extend from 1 to 5 kilometers along a shoreline. (Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999)

Communication and Perception

Eurasian beavers communicate mainly through chemical communication. Not only do they use castoreum to mark territory, but they also use their oil glands to distinguish between males and females. Eurasian beavers also use postures, tail slapping, and vocalizations. Vocalizations include whining calls, whistling, and hissing. Tail slapping is used when they are frightened or upset. (Nolet, 2000; Nowak, 1999)

Food Habits

Eurasian beavers are herbivores, feeding primarily on woody vegetation in the winter months. Eurasian beavers prefer willow, aspen, and birch trees with diameters less than 10 cm. These food items are stored in the water during the fall months in large quantities. These food caches need to be large enough to last the entire colony until the ice melts in the spring of the year. During summer months beavers feed heavily on aquatic vegetation, shoots, twigs, bark, leaves, buds, and roots. In agricultural areas beavers will consume crops as well. Beavers prefer herbaceous plant foods over woody vegetation when it is available. Beavers do not have cellulases, an enzyme used to break down cellulose. However beavers are coprophagous, taking up caecal microbes during reingestion which help break down cellulose that can be absorbed after reingestion. (Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000; Rue, 2002)

  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • fruit
  • flowers
  • Other Foods
  • dung


Lodges and burrows in the bank make beavers mostly inaccessible to predators. By far the most successful predators of Eurasian beavers are humans. Eurasian beavers were hunted and trapped nearly to extinction for their prized pelts and castoreum. Today, with conservation efforts in place, Eurasian beavers are protected by law. Poaching, entanglement in nets, and road accidents are the leading causes of death. Natural predators are wolves, brown bear, and red foxes. The leading cause of death in C. fiber today is infectious disease. Eurasian beavers use a “tail slap” when they are frightened, which is a warning to all other beavers that something is near. Beavers slap the water surface with the tail as they dive under water and out of harms way. In response, all beavers in the area will do the same. Eurasian beavers will also avoid food items that have the odors of predators on them. (Ducroz, et al., 2005; Muller-Schwarze and Sun, 2003; Nolet, 2000; Nowak, 1999)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Eurasian beavers have the ability to impact ecosystems tremendously. Through the process of building dams they alter the flow of the water and flood many acres of former uplands. Dams build up sediments and debris which increase carbon and decrease available nitrogen and acidity. This changes the invertebrate community from running water invertebrates to still water invertebrates. This new water source attracts new species of birds, fish, and amphibians by providing a suitable water table. Eurasian beavers maintain certain woody vegetation in the sapling stages for extended periods of time through their browsing activities. Flooded timber will die off in a year and soon a once forested ecosystem becomes an open water ecosystem. Eurasian beavers can also alter, in time, the stand structure around the waters edge. They do this through their food selection, making conditions favorable for unselected food items. Eurasian beavers start with a small stream and build a dam, flooding a forested area. Once the beavers use up available resources, they move on and abandon the pond. Succession in the pond leads to the development of marsh habitat and then meadow. The decrease in nitrogen and acidity along with the increase in carbon hinders the growth of woody vegetation for some time but eventually woody vegetation begins to grow forest is regenerated. (Middleton, 1999; Nolet, 2000; Nowak, 1999)

Eurasian beavers are hosts to mites, with up to 33 different species of mites that could be living on them at anytime. (Muller-Schwarze and Sun, 2003; Nowak, 1999)

Commensal/Parasitic Species
  • mites (Acari)

Economic Importance for Humans: Positive

Eurasian beavers were heavily trapped and hunted for their pelts, castoreum, and meat. Pelts were sold and even used as currency right up to their near extinction. Furs were used to make garments, felt, and, most notably, felt hats. Castoreum was used as a medicine and a base for perfumes. Beaver meat was also prized as food. In the 16th century the Pope claimed, due to the scaly tail and semi aquatic life style, that beaver could be considered a fish and be eaten during Catholic fasting days. Even today 400 tons of beaver meat are consumed during lent every year in Europe. (Ducroz, et al., 2005; Muller-Schwarze and Sun, 2003; Nolet, 2000)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Eurasian beavers can be destructive when they cut down trees and flood areas. They may be removed for nuisance behavior. The most numerous nuisance complaints are flooding farm lands and crop destruction from eating and flooding. Eurasian beavers also flood roadways and culverts and can cause extensive timber damage. (Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000)

  • Negative Impacts
  • crop pest

Conservation Status

The IUCN redlist considers Eurasian beavers a species of least concern with increasing populations and sufficient protection, although Asian populations remain small and relatively unprotected. Populations throughout their former range have not returned to their previous numbers. Mongolian beavers (Castor fiber birulai) are considered endangered by the U.S. Fish and Wildlife Service. (Ducroz, et al., 2005; Long, 2003; Muller-Schwarze and Sun, 2003; Nolet, 2000)


Josh Holden (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), Animal Diversity Web.



living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate

cooperative breeder

helpers provide assistance in raising young that are not their own


an animal that mainly eats the dung of other animals


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


an animal that mainly eats leaves.


A substance that provides both nutrients and energy to a living thing.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).


marshes are wetland areas often dominated by grasses and reeds.


Having one mate at a time.


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born


AnAge database, 2009. "AnAge entry for Castor fiber" (On-line). AnAge: The Animal Ageing and Longevity Database. Accessed September 30, 2009 at

Ducroz, J., M. Stubbe, A. Saveljev, D. Heidecke, R. Samjaa, A. Ulevicius, A. Stubbe, W. Durka. 2005. Genetic variation and population structure of the eurasian beaver Castor fiber in eastern europe and Asia. Journal of Mammology, 86/6: 1059-1067.

Long, J. 2003. Introduced Mammals of the World: Their History, Distribution, and Influence. United Kingdom: CABI Publishing.

Middleton, B. 1999. Wetland Restoration: Pulse Flooding and, Disturbance Dynamics. New Jersey: Wiley. Accessed August 10, 2009 at

Muller-Schwarze, D., L. Sun. 2003. The Beaver: Natural History of a Wetlands Engineer. Ithaca and London: Cornell University Press.

Nolet, B. 2000. "Management of the Beaver (Castor fiber): Towards restoration of it's former distribution and ecological funtion in Europe" (On-line pdf). Accessed August 09, 2009 at

Nowak, R. 1999. Walker's Mammals of the World. Sixth Edition. Baltimore: The Johns Hopkins University Press.

Rue, L. 2002. Beavers. Stillwater, Minnesota: Voyageur Press. Accessed August 09, 2009 at