Animal Diversity Web

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)

• Biogeographic Regions
• palearctic
  • native

Habi­tat

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)

• Habitat Regions
• temperate
• freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh
• swamp

• Other Habitat Features
• riparian

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)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• 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

Re­pro­duc­tion

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)

• Mating System
• monogamous
• cooperative breeder

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)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

• 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

  3

• Average number of offspring

  3

  AnAge

• 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

Lifes­pan/Longevity

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

Be­hav­ior

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)

• Key Behaviors
• natatorial
• nocturnal
• motile
• sedentary
• territorial
• social
• dominance hierarchies

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)

• Communication Channels
• visual
• acoustic
• chemical

• Other Communication Modes
• scent marks

• Perception Channels
• visual
• tactile
• acoustic
• chemical

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)

• Primary Diet
• herbivore
  • folivore
  • lignivore
• coprophage

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

• Other Foods
• dung

• Foraging Behavior
• stores or caches food

Pre­da­tion

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

• Known Predators

  • humans (Homo sapiins)
  • Eurasian wolves (Canis lupus)
  • brown bears (Ursus arctos)
  • red foxes (Vulpes vulpes)

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)

• Ecosystem Impact
• creates habitat
• keystone species

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)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  Endangered

• CITES

  No special status

Con­trib­u­tors

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

Ref­er­ences

AnAge data­base, 2009. "AnAge entry for Cas­tor fiber" (On-line). AnAge: The An­i­mal Age­ing and Longevity Data­base. Ac­cessed Sep­tem­ber 30, 2009 at http://​genomics.​senescence.​info/​species/​entry.​php?​species=Castor_​fiber.

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 http://​books.​google.​com/​books?​id=Zv_​aJg7dtM8C&​pg=PA41&​dq=Castor+fiber+predation&​lr=#​v=onepage&​q=&​f=false.

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 http://​books.​google.​com/​books?​id=JDHuVsOfbakC&​pg=PA5&​dq=Castor+fiber&​lr=#​v=onepage&​q=&​f=false.

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 http://​books.​google.​com/​books?​id=VMk92ARQajEC&​pg=PA9&​dq=Castor+fiber+predation&​lr=#​v=onepage&​q=&​f=false.