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{{Short description|Genus of mammal}}
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{{Use mdy dates|date=February 2021}}
{{Use American English|date=December 2020}}
{{Automatic taxobox
| name             =Beaver
| fossil_range     ={{small|Late [[Miocene]]{{snd}}Recent}}
| image            =American Beaver.jpg
| image_caption    =[[North American beaver]] (''Castor canadensis'')
| taxon            =Castor
| authority        =[[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
| subdivision_ranks=Species
| subdivision      = {{ubl|''[[North American beaver|C. canadensis]]'' – North American beaver|''[[Eurasian beaver|C. fiber]]'' – Eurasian beaver|{{extinct}}''[[Castor californicus|C. californicus]]''|{{extinct}}''[[Castor praefiber|C. praefiber]]''|{{extinct}}''[[Castor neglectus|C. neglectus]]''}}
| range_map=Castor range.png
| range_map_caption=Range of the living beavers as of 2016 (including introduced ''C. canadensis'' populations in Europe and Patagonia, but missing ''C. fiber'' populations in Mongolia and northwestern China, as well as reintroduced populations in the United Kingdom){{Update inline|date=March 2023|?=yes|reason=See discussion on talk page.}}
| type_species=''[[Castor fiber]]''<ref>{{cite journal |author1=International Commission on Zoological Nomenclature |title=Opinion 75. Twenty-Seven Generic Names of Protozoa, Vermes, Pisces, Reptilia and Mammalia Included in the Official List of Zoological Names |journal=Smithsonian Miscellaneous Collections |date=1922 |volume=73 |issue=1 |pages=35–37 |url=https://www.biodiversitylibrary.org/page/8910949 |access-date=January 23, 2022 |archive-date=January 23, 2022 |archive-url=https://web.archive.org/web/20220123181504/https://www.biodiversitylibrary.org/page/8910949 |url-status=live }}</ref>
| type_species_authority=[[Carl Linnaeus|Linnaeus]], 1758
}}

'''Beavers''' (genus '''''Castor''''') are large, [[semiaquatic]] [[rodents]] of the [[Northern Hemisphere]]. There are two existing [[species]]: the [[North American beaver]] (''Castor canadensis'') and the [[Eurasian beaver]] (''C. fiber''). Beavers are the second-largest living rodents, after [[Hydrochoerus|capybaras]], weighing up to {{convert|50|kg|abbr=on}}. They have stout bodies with large heads, long chisel-like [[incisors]], brown or gray [[fur]], hand-like front feet, [[Webbed foot|webbed]] back feet, and tails that are flat and scaly. The two species differ in skull and tail shape and fur color. Beavers can be found in a number of [[Freshwater ecosystem|freshwater habitats]], such as rivers, streams, lakes and ponds. They are [[herbivorous]], consuming [[Bark (botany)|tree bark]], [[aquatic plants]], grasses and [[sedges]].

Beavers build [[Beaver dam|dams]] and lodges using tree branches, vegetation, rocks and mud; they chew down trees for building material. Dams restrict water flow, forming ponds, and lodges (usually built in ponds) serve as shelters. Their infrastructure creates [[wetland]]s used by many other species, and because of their effect on other organisms in the [[ecosystem]], beavers are considered a [[keystone species]]. Adult males and females live in [[Pair bond|monogamous pairs]] with their offspring. After their first year, the young help their parents repair dams and lodges; older siblings may also help raise newly born offspring. Beavers hold [[Territory (animal)|territories]] and mark them using scent mounds made of mud, debris, and [[castoreum]]—a liquid substance excreted through the beaver's [[urethra]]-based castor sacs. Beavers can also recognize their kin by their [[anal gland]] secretions and are more likely to tolerate them as neighbors.

Historically, beavers have been hunted for their fur, meat, and castoreum. Castoreum has been used in medicine, perfume, and food flavoring; beaver pelts have been a major driver of the [[fur trade]]. Before protections began in the 19th and early 20th centuries, [[overhunting]] had nearly exterminated both species. Their populations have since rebounded, and they are listed as species of [[Least-concern species|least concern]] by the [[IUCN Red List]] of mammals. In human culture, the beaver symbolizes industriousness, especially in connection with construction; it is the [[national animal]] of [[Canada]].

== Etymology ==
The English word ''beaver'' comes from the [[Old English]] word {{lang|ang|beofor}} or {{lang|ang|befor}} and is connected to the [[German language|German]] word {{lang|de|biber}} and the [[Dutch language|Dutch]] word {{lang|nl|bever}}. The ultimate origin of the word is an [[Proto-Indo-European language|Indo-European]] root for {{gloss|brown}}.<ref>{{cite web |title=Beaver |website=[[Lexico]] |access-date=September 4, 2021|url=https://www.lexico.com/definition/beaver|archive-url=https://web.archive.org/web/20201028140138/https://www.lexico.com/definition/beaver|archive-date=October 28, 2020}}</ref> [[Cognate]]s of ''beaver'' are the source for several European [[placenames]], including those of [[Beverley]], [[Bièvres (disambiguation)|Bièvres]], [[Biberbach (disambiguation)|Biberbach]], [[Biebrich (disambiguation)|Biebrich]], [[Bibra (disambiguation)|Bibra]], [[Bibern (disambiguation)|Bibern]], [[Bibrka]], [[Bobr (disambiguation)|Bobr]], [[Bober (disambiguation)|Bober]], [[Bóbrka (disambiguation)|Bóbrka]], [[Bjurholm]], [[Bjurälven]], and [[Bjurum]].{{sfn|Poliquin|2015|p=21}} The [[genus]] name ''Castor'' has its origin in the Greek word {{lang|el|κάστωρ}} {{transliteration|grc|kastōr}} and translates as {{gloss|beaver}}.<ref>{{cite web |title=Castor |website=[[Lexico]] |access-date=January 22, 2021 |url=https://www.lexico.com/definition/castor |archive-url=https://web.archive.org/web/20210208112633/https://www.lexico.com/definition/castor |archive-date=February 8, 2021}}</ref>

== Taxonomy ==
[[Carl Linnaeus]] coined the genus name ''Castor'' as well as the [[specific epithet|specific (species) epithet]] ''fiber'' for the Eurasian species.<ref name="ITISfiber">{{cite web|title=Castor fiber|url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=573165#null|url-status=live|archive-url=https://web.archive.org/web/20201103070634/https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=573165#null|archive-date=November 3, 2020|access-date=September 21, 2020|website=ITIS}}</ref> German zoologist [[Heinrich Kuhl]] coined ''C. canadensis'' in 1820.<ref name="ITIScandensis">{{cite web|title=Castor canadensis|url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=180212#null|url-status=live|archive-url=https://web.archive.org/web/20201103070405/https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=180212#null|archive-date=November 3, 2020|access-date=September 21, 2020|website=ITIS}}</ref> Many scientists considered both names synonymous for one same species{{sfn|Poliquin|2015|pp=79–80}}<ref name="MacDonald"/> until the 1970s, when [[Chromosome#Number in various organisms|chromosomal]] evidence became available confirming both as separate where the Eurasian has 48 chromosomes, while the North American has 40. The difference in chromosome numbers prevents them from interbreeding.<ref>{{cite journal|last1=Lahti|first1=S.|last2=Helminen|first2=M.|year=1974|title=The beaver ''Castor fiber'' (L.) and ''Castor canadensis'' (Kuhl) in Finland|journal=Acta Theriologica|volume=19|issue=4|pages=177–189|doi=10.4098/AT.ARCH.74-13|doi-access=free}}</ref> Twenty-five subspecies have been classified for ''C. canadensis'', and nine have been classified for ''C. fiber''.<ref name="ITISfiber"/><ref name="ITIScandensis"/>

There are two [[Extant taxa|extant]] species: the [[North American beaver]] (''Castor canadensis'') and the [[Eurasian beaver]] (''C. fiber''). The Eurasian beaver is slightly longer and has a more lengthened skull, triangular [[nasal cavity|nasal cavities]] (as opposed to the square ones of the North American species), a lighter fur color, and a narrower tail.{{sfn|Runtz|2015|pp=22–25}}

===Evolution===
{{multiple image
| align     =right
| direction =horizatonal
| width     =220
| image1    =Castor canadensis1.jpg
| caption1  =North American beaver (''Castor canadensis'')
| alt1      =North American Beaver on a river bank
| image2    =Castor fiber eating in Eskilstuna, Sweden.jpg
| caption2  =Eurasian beaver (''Castor fiber'')
| alt2      =A Eurasian Beaver gnawing on a branch
}}
{{cladogram|caption=Phylogeny of extant and extinct relatives of modern beavers based on genetics and morphology.<ref name="Fabre">{{Cite journal|last1=Fabre |first1=Pierre-Henri |last2=Hautier |first2=Lionel |last3=Dimitrov |first3=Dimitar |last4=Douzery |first4=Emmanuel J. P.  |year=2012 |title= A glimpse on the pattern of rodent diversification: a phylogenetic approach |journal=[[BMC Evolutionary Biology]] |volume=12 |number=88 |page=88 |doi=10.1186/1471-2148-12-88 |pmid=22697210 |pmc=3532383 |doi-access=free |bibcode=2012BMCEE..12...88F }}</ref><ref name=Rybczynski/>
|cladogram={{clade|style=width:500px;
      |label1=[[Castorimorpha]]
      |1={{clade
        |label1=[[Castoroidea]]
        |1={{clade
           |label1=[[Castoridae]]<!--[[File:Die Gartenlaube (1858) b 068 white background.jpg|50px]]-->
           |1={{clade
              |1=''Agnotocastor coloradensis''
              |2={{clade
                 |1={{clade
                    |1=''Agnotocastor praetereadens''
                    |2={{clade
                       |1=''[[Anchitheriomys]]'' sp. [[File:Anchitheriomys.JPG|50px]]
                       |2={{clade
                          |1=[[Castorinae]] (modern beavers) [[File:Die Gartenlaube (1858) b 068 white background.jpg|50px]]
                          |2=[[Castoroidinae]] [[File:Giant-beaver-fieldmuseum.jpg|50px]]
                          }}
                       }}
                    }}
                 |2={{clade
                    |1=''[[Agnotocastor]]'' sp.
                    |2={{clade
                       |1=''[[Migmacastor procumbodens]]''
                       |2=Palaeocastorinae [[File:Palaeocastor fossor.jpg|50px]]
                       }}
                    }}
                 }}
              }}
           }}
        |label2=[[Geomyoidea]]
        |2={{clade
          |1=[[Heteromyidae]] (kangaroo rats and allies) [[File:Image taken from page 108 of 'Report of an expedition down the Zuni and Colorado Rivers by Captain L. Sitgreaves (white background).jpg|50px]]
          |2=[[Geomyidae]] (gophers) [[File:Western pocket gopher.jpg|50px]]
           }}
     }}
}}
}}
Beavers belong to the rodent suborder [[Castorimorpha]], along with [[Heteromyidae]] ([[kangaroo rats]] and [[kangaroo mice]]), and the [[gophers]]. Modern beavers are the only extant members of the family [[Castoridae]]. They originated in North America in the late [[Eocene]] and colonized Eurasia via the [[Bering Land Bridge]] in the early [[Oligocene]], coinciding with the ''[[Grande Coupure]]'', a time of significant changes in animal species around 33{{spaces}}million years ago ([[myr]]).<ref name="Doronina 2017">{{cite journal |last1=Doronina |first1=Liliya |last2=Matzke |first2=Andreas |last3=Churakov |first3=Gennady |last4=Stoll |first4=Monika |last5=Huge |first5=Andreas |last6=Schmitz |first6=Jürgen |title=The beaver's phylogenetic lineage ''illumina''ted by retroposon reads |journal=[[Scientific Reports]] |year=2017 |volume=7 |issue=1 |article-number=43562 |doi=10.1038/srep43562|pmid=28256552 |pmc=5335264 |bibcode=2017NatSR...743562D |doi-access=free}}</ref><ref name=Korth2002/>

The more [[Basal (phylogenetics)|basal]] castorids had several unique features: more complex [[Occlusion (dentistry)|occlusion]] between cheek teeth, parallel rows of upper teeth, premolars that were only slightly smaller than molars, the presence of a third set of premolars (P3), a [[Foramen|hole]] in the [[stapes]] of the inner ear, a smooth [[palatine bone]] (with the palatine opening closer to the rear end of the bone), and a longer [[Rostrum (anatomy)#Vertebrates|snout]]. More [[Synapomorphy and apomorphy|derived]] castorids have less complex occlusion, upper tooth rows that create a V-shape towards the back, larger second premolars compared to molars, absence of a third premolar set and stapes hole, a more grooved palatine (with the opening shifted towards the front), and reduced [[incisive foramen]]. Members of the subfamily ''Palaeocastorinae'' appeared in late-Oligocene North America. This group consisted primarily of smaller animals with relatively large front legs, a flattened skull, and a reduced tail—all features of a [[fossorial]] (burrowing) lifestyle.<ref name=Korth2002>{{cite journal |last=Korth |first=W. W. |year=2002 |title=Comments on the systematics and classification of the beavers (Rodentia, Castoridae) |journal=[[Journal of Mammalian Evolution]] |volume=8 |issue=4 |pages=279–296 |doi=10.1023/A:1014468732231 |s2cid=27935955}}</ref>

In the early [[Miocene]] (about 24 mya), castorids [[Evolution|evolved]] a [[semiaquatic]] lifestyle. Members of the subfamily [[Castoroidinae]] are considered to be a [[sister group]] to modern beavers, and included giants like ''[[Castoroides]]'' of North America and ''[[Trogontherium]]'' of Eurasia.<ref name=Rybczynski>{{cite journal |last=Rybczynski |first=N. |year=2007|title=Castorid phylogenetics: Implications for the evolution of swimming and tree-exploitation in beavers|journal=[[Journal of Mammalian Evolution]] |volume=14 |pages=1–35 |doi=10.1007/s10914-006-9017-3 |s2cid=33659669}}</ref><ref name=Korth2002/> ''Castoroides'' is estimated to have had a length of {{convert|1.9|–|2.2|m|ft|1|abbr=on}} and a weight of {{convert|90|–|125|kg|lb|0|abbr=on}}.<ref name="R&S">{{cite journal |last1=Swinehart |first1=A. L. |last2=Richards |first2=R. L. |title=Paleoecology of Northeast Indiana Wetland Harboring Remains of the Pleistocene Giant Beaver (Castoroides Ohioensis) |journal=[[Proceedings of the Indiana Academy of Science]] |date=2001 |volume=110 |page=151 |url=https://journals.iupui.edu/index.php/ias/article/download/7219/7239 |access-date=November 21, 2014 |archive-date=March 4, 2016 |archive-url=https://web.archive.org/web/20160304084347/https://journals.iupui.edu/index.php/ias/article/download/7219/7239 |url-status=live }}</ref> Fossils of one genus in Castoroidinae, ''[[Dipoides]]'', have been found near piles of chewed wood,<ref name=Rybczynski/> though ''Dipoides'' appears to have been an inferior woodcutter compared to ''Castor''. Researchers suggest that modern beavers and Castoroidinae shared a bark-eating [[Lowest common ancestor|common ancestor]]. Dam and lodge-building likely developed from bark-eating, and allowed beavers to survive in the harsh winters of the [[subarctic]]. There is no conclusive evidence for this behavior occurring in non-''Castor'' species.<ref name=Plint2020>{{Cite journal|last1=Plint|first1=Tessa|last2=Longstaffe|first2=Fred J.|last3=Ballantyne|first3=Ashley|last4=Telka|first4=Alice|last5=Rybczynski|first5=Natalia|year=2020|title=Evolution of woodcutting behaviour in Early Pliocene beaver driven by consumption of woody plants|journal=[[Scientific Reports]]|volume=10|number=13111|page=13111|doi=10.1038/s41598-020-70164-1|pmid=32753594|pmc=7403313|bibcode=2020NatSR..1013111P|issn=2045-2322|doi-access=free}}</ref>

The genus ''Castor'' likely originated in [[Eurasia]].<ref name="speciation"/> The earliest fossil remains appear to be ''C. neglectus'', found in Germany and dated 12–10 mya.<ref>{{cite journal|last1=Samuels|first1=J. X.|last2=Zancanella|first2=J.|year=2011|title=An early Hemphillian occurrence of ''Castor'' (Castoridae) from the Rattlesnake Formation of Oregon|journal=Journal of Paleontology|volume=85|issue=5|pages=930–935|doi=10.1666/11-016.1|s2cid=128866799}}</ref> [[Mitochondrial DNA]] studies place the common ancestor of the two living species at around 8 mya. The ancestors of the North American beaver would have crossed the Bering Land Bridge around 7.5 mya.<ref name="speciation">{{cite journal |last1=Horn |first1=S. |last2=Durke |first2=W. |last3=Wolf |first3=R. |last4=Ermala |first4=A. |last5=Stubbe |first5=M. |last6=Hofreiter |first6=M. |title=Mitochondrial Genomes Reveal Slow Rates of Molecular Evolution and the Timing of Speciation in Beavers (''Castor''), One of the Largest Rodent Species|journal=[[PLOS ONE]]|year=2011 |volume=6 |issue=1 |article-number=e14622|doi=10.1371/journal.pone.0014622|pmid=21307956 |pmc=3030560 |bibcode=2011PLoSO...614622H |doi-access=free }}</ref> ''Castor'' may have competed with members of Castoroidinae, which led to [[niche differentiation]].<ref>{{cite journal|last1=Samuels|first1=J. X.|last2=Van Valkenburgh|first2=B.|year=2008|title=Skeletal indicators of locomotor adaptations in living and extinct rodents|journal=[[Journal of Morphology]]|volume=269|issue=11 |pages=1387–1411|doi=10.1002/jmor.10662| pmid=18777567|s2cid=36818290}}</ref> The fossil species ''C. praefiber'' was likely an ancestor of the Eurasian beaver.<ref>{{cite journal|last1=Barisone|first1=G.|last2=Argenti|first2=P.|last3=Kotsakis|first3=T.|year=2006|title=Plio-Pleistocene evolution of the genus ''Castor'' (Rodentia, Mammalia) in Europe: ''C. fiber plicidens'' of Pietrafitta (Perugia, Central Italy)|journal=[[Geobios]]|volume=39|issue=6|pages=757–770|doi=10.1016/j.geobios.2005.10.004|bibcode=2006Geobi..39..757B }}</ref> ''[[Castor californicus|C. californicus]]'' from the [[Early Pleistocene]] of North America was similar to but larger than the extant North American beaver.<ref name=K&A>{{cite book | author=Kurtén, B. | author-link=Björn Kurtén | author2=Anderson, E.   | title=Pleistocene Mammals of North America | location=New York | publisher=[[Columbia University Press]] | year=1980 | pages=236–237 | isbn=978-0-231-03733-4|oclc=5830693}}</ref>'

==Characteristics==

[[File:Beaver skeleton.jpg|thumb|left|alt=see caption|Mounted North American beaver skeleton.]]

Beavers are the second-largest living rodents, after [[Hydrochoerus|capybara]]s. They have a head–body length of {{convert|80|–|120|cm|abbr=on}}, with a {{convert|25|–|50|cm|0|abbr=on}} tail, a shoulder height of {{convert|30|–|60|cm|abbr=on}}, and generally weigh {{convert|11|–|30|kg|abbr=on}},<ref name="MacDonald">{{Cite book |last1=Busher |first1=P. |url=https://archive.org/details/encyclopediaofma0000unse_m0x7/page/590/mode/2up |title=The Encyclopedia of Mammals |last2=Hartman |first2=G. |publisher=[[Oxford University Press]] |year=2001 |isbn=978-0-7607-1969-5 |editor=MacDonald |editor-first=D. W. |edition=2nd |pages=590–593 |contribution=Beavers}}</ref> but can be as heavy as {{convert|50|kg|lb|abbr=on}}. Males and females are almost identical externally.{{sfn|Müller-Schwarze|Sun|2003|pp=10, 14}} Their bodies are streamlined like [[marine mammal]]s and their robust build allows them to pull heavy loads.<ref name=JohnHopkins/>{{sfn|Runtz|2015|p=73}} A beaver [[Animal coat|coat]] has 12,000–23,000 hairs/cm<sup>2</sup> (77,000–148,000 hairs/in<sup>2</sup>) and functions to keep the animal warm, to help it float in water, and to protect it against predators. [[Guard hairs]] are {{convert|5|–|6|cm|abbr=on}} long and typically reddish brown, but can range from yellowish brown to nearly black. The [[underfur]] is {{convert|2|–|3|cm|1|abbr=on}} long and dark gray. Beavers [[molt]] every summer.<ref name="MacDonald"/>{{sfn|Müller-Schwarze|Sun|2003|pp=12–13}}

Beavers have large skulls with powerful [[Muscles of mastication|chewing muscles]]. They have four chisel-shaped incisors that continue to grow throughout their lives. The incisors are covered in a thick [[tooth enamel|enamel]] that is colored orange or reddish-brown by iron compounds.{{sfn|Müller-Schwarze|Sun|2003|pp=11–12}}<ref>{{cite journal |last1=Gordon |first1=L. M. |last2=Cohn |first2=M. J.|last3=MacRenaris |first3=K. W. |last4=Pasteris |first4=J. D. |last5=Seda |first5=T. |last6=Joester |first6=D. |year=2015 |title=Amorphous intergranular phases control the properties of rodent tooth enamel|journal=[[Science (journal)|Science]] |volume=347 |issue=6223 |pages=746–750 |doi=10.1126/science.1258950 |pmid=25678658 |bibcode=2015Sci...347..746G |s2cid=8762487|doi-access=free }}</ref> The lower incisors have roots that are almost as long as the entire lower jaw. Beavers have one premolar and three molars on all four sides of the jaws, adding up to 20 teeth. The molars have meandering ridges for grinding woody material.{{sfn|Müller-Schwarze|Sun|2003|p=12}} The eyes, ears and nostrils are arranged so that they can remain above water while the rest of the body is submerged. The nostrils and ears have valves that close underwater, while [[nictitating membranes]] cover the eyes. To protect the [[larynx]] and [[trachea]] from water flow, the [[epiglottis]] is contained within the nasal cavity instead of the throat. In addition, the back of the tongue can rise and create a waterproof seal. A beaver's lips can close behind the incisors, preventing water from entering their mouths as they cut and bite onto things while submerged.{{sfn|Runtz|2015|p=55}}<ref name=Pelagic/>

[[File:Picture Natural History - No 40 41 42 - Beaver feet and tail.png|thumb|right|alt=Illustration of a fore foot, a hind foot showing webbing, and the tail of a beaver|The fore foot, hind foot, and tail of a beaver.]]
[[File:Beaver tail print on snow.jpg|thumb|Beaver tail and footprints on snow.]]

The beaver's front feet are dexterous, allowing them to grasp and manipulate objects and food, as well as dig. The hind feet are larger and have [[webbed foot|webbing between the toes]], and the second innermost toe has a "double nail" used for grooming.<ref name=Pelagic/>{{sfn|Runtz|2015|p=71}} Beavers can swim at {{cvt|8|km/h|0|abbr=on}};{{sfn|Runtz|2015|p=73}} only their webbed hind feet are used to swim, while the front feet fold under the chest.<ref name=Pelagic>{{cite book|last1=Campbell-Palmer|first1=Róisín|last2=Gow|first2=Derek|last3=Needham|first3=Robert|last4=Jones|first4=Simon|last5=Rosell|first5=Frank|date=2015|title=The Eurasian Beaver|publisher=Pelagic Publishing Ltd|pages=7–12|isbn=978-1-78427-040-7}}</ref> On the surface, the hind limbs thrust one after the other; while underwater, they move at the same time.<ref>{{cite journal|last1=Allers|first1=D.|last2=Culik|first2=B. M.|year=1997|title=Energy Requirements of Beavers (''Castor canadensis'') Swimming Underwater |journal=[[Physiological Zoology]]|volume=70|issue=4|pages=456–463|doi=10.1086/515852|pmid=9237306|s2cid=21784970}}</ref> Beavers are awkward on land but can move quickly when they feel threatened. They can carry objects while walking on their hind legs.<ref name=JohnHopkins>{{cite book |last1=Baker |first1=B. W. |last2=Hill|first2=E. P.|contribution=Beaver ''Castor canadensis'' |title=Wild Mammals of North America: Biology, Management, and Conservation|editor1-last=Feldhamer |editor1-first=G. A.|editor2-last=Thompson|editor2-first=B. C.|editor3-last=Chapman|editor3-first=J. A.|publisher=[[Johns Hopkins University Press]]|edition=2|year=2003|pages=289–297 |isbn=978-0-8018-7416-1|oclc=51969059}}</ref><ref name=Pelagic/>

The beaver's distinctive tail has a conical, muscular, hairy base; the remaining two-thirds of the appendage is flat and scaly. The tail has multiple functions: it provides support for the animal when it is upright (such as when chewing down a tree), acts as a rudder when it is swimming, and stores fat for winter. It also has a [[countercurrent exchange|countercurrent]] blood vessel system which allows the animal to lose heat in warm temperatures and retain heat in cold temperatures.{{sfn|Runtz|2015|pp=55, 63–67}}

The beaver's sex organs are inside the body, and the male's penis has a cartilaginous [[baculum]]. They have only one opening, a [[cloaca]], which is used for reproduction, scent-marking, defecation, and urination. The cloaca evolved secondarily, as most mammals have lost this feature, and may reduce the area vulnerable to infection in dirty water. The beaver's intestine is six times longer than its body, and the [[caecum]] is double the volume of its stomach.{{sfn|Müller-Schwarze|Sun|2003|pp=13–14, 17, 44}} Microorganisms in the caecum allow them to process around 30 percent of the [[cellulose]] they eat.<ref name=JohnHopkins/> A beaver defecates in the water, leaving behind balls of sawdust. Female beavers have four [[mammary glands]]; these produce milk with 19 percent fat, a higher fat content than other rodents. Beavers have two pairs of glands: castor sacs, which are part of the urethra, and [[anal gland]]s. The castor sacs secrete [[castoreum]], a liquid substance used mainly for marking territory. Anal glands produce an oily substance which the beaver uses as a waterproof ointment for its coat. The substance plays a role in individual and family recognition. Anal secretions are darker in females than males among Eurasian beavers, while the reverse is true for the North American species.{{sfn|Müller-Schwarze|Sun|2003|pp=6, 13–14, 41–45}}
[[File:Castor fiber vistulanus3.jpg|thumb|left|Eurasian beaver swimming.|alt=Beaver swimming]]
Compared to many other rodents, a beaver's brain has a [[hypothalamus]] that is much smaller than the [[cerebrum]]; this indicates a relatively advanced brain with higher intelligence. The [[cerebellum]] is large, allowing the animal to move within a three-dimensional space (such as underwater) similar to tree-climbing squirrels. The [[neocortex]] is devoted mainly to [[Somatosensory system|touch]] and hearing. Touch is more advanced in the lips and hands than the [[whiskers]] and tail. Vision in the beaver is relatively poor; the beaver eye cannot see as well underwater as an [[otter]]. Beavers have a good sense of smell, which they use for detecting land predators and for inspecting scent marks, food, and other individuals.{{sfn|Müller-Schwarze|Sun|2003|pp=11, 14–15}}

Beavers can hold their breath for as long as 15 minutes but typically remain underwater for no more than five or six minutes.{{sfn|Runtz|2015|p=74}} Dives typically last less than 30 seconds and are usually no more than {{convert|1|m|abbr=on}} deep.<ref>{{cite journal|last1=Graf|first1=P. M.|last2=Wilson|first2=R. P.|last3=Sanchez|first3=L. C.|last4=Hacklӓnder|first4=K.|last5=Rosell|first5=F.|year=2017|title=Diving behavior in a free-living, semi-aquatic herbivore, the Eurasian beaver ''Castor fiber''|journal=Ecology and Evolution|volume=8|issue=2|pages=997–1008|doi=10.1002/ece3.3726|pmid=29375773|pmc=5773300|doi-access=free}}</ref> When diving, their heart rate decreases to 60 beats per minute, half its normal pace, and blood flow is directed more towards the brain. A beaver's body also has a high tolerance for carbon dioxide. When surfacing, the animal can replace 75 percent of the air in its lungs in one breath, compared to 15 percent for a human.<ref name=Pelagic/>{{sfn|Runtz|2015|p=74}}

==Distribution and status==

[[File:Beaver near Swan Lake (33797143245).jpg|thumb|right|alt=A beaver at the shores of a lake|North American beaver in [[Yellowstone National Park]].]]

The [[IUCN Red List]] of mammals lists both beaver species as [[Least-concern species|least concern]].<ref name=iucn-canadensis>{{cite iucn |author=Cassola, F.|title=''Castor canadensis'' |volume=2016 |article-number=e.T4003A22187946 |year=2016 |doi=10.2305/IUCN.UK.2016-3.RLTS.T4003A22187946.en}}</ref><ref name=iucn-fiber>{{cite iucn |author=Batbold, J. |author2=Batsaikhan, N. |author3=Shar, S. |author4=Hutterer, R. |author5=Kryštufek, B. |author6=Yigit, N. |author7=Mitsainas, G. |author8=Palomo, L. |year=2021 |amends=2016 |title=''Castor fiber'' |article-number=e.T4007A197499749 |doi=10.2305/IUCN.UK.2021-1.RLTS.T4007A197499749.en}}</ref> The North American beaver is widespread throughout most of the United States and Canada and can be found in northern Mexico. The species was introduced to Finland in 1937 (and then spread to northwestern Russia) and to [[Tierra del Fuego|Tierra del Fuego, Patagonia]], in 1946.<ref name=iucn-canadensis/> {{As of|2019}}, the introduced population of North American beavers in Finland has been moving closer to the habitat of the Eurasian beaver.<ref>{{cite journal|last1=Alakoski|first1=R.|last2=Kauhala|first2=K.|last3=Selonen|first3=V.|year=2019|title=Differences in habitat use between the native Eurasian beaver and the invasive North American beaver in Finland|journal=Biological Invasions|volume=21|issue=5|pages=1601–1613|doi=10.1007/s10530-019-01919-9|doi-access=free|bibcode=2019BiInv..21.1601A }}</ref> Historically, the North American beaver was trapped and nearly extirpated because its fur was highly sought after. Protections have allowed the beaver population on the continent to rebound to an estimated 6–12{{spaces}}million by the late 20th century; still far lower than the originally estimated 60–400{{spaces}}million North American beavers before the fur trade.<ref name=Naiman>{{cite journal |title=Alteration of North American Streams by Beaver |author1=Naiman, Robert J. |author2=Johnston, Carol A. |author2-link=Carol A. Johnston |author3=Kelley, James C. |journal=[[BioScience]] |date=Dec 1988 |pages=753–762 |doi=10.2307/1310784 |url=http://www.landscouncil.org/documents/Beaver_Project/Articles/Naiman_et_al_1988_alter_n_american_streams_by_beaver.pdf |access-date=February 28, 2010 |volume=38 |issue=11 |jstor=1310784 |archive-url=https://web.archive.org/web/20120304035814/http://www.landscouncil.org/documents/Beaver_Project/Articles/Naiman_et_al_1988_alter_n_american_streams_by_beaver.pdf |archive-date=March 4, 2012}}</ref> The introduced population in Tierra del Fuego is estimated at 35,000–50,000 individuals {{As of|2016|lc=y}}.<ref name=iucn-canadensis/>

The Eurasian beaver's range historically included much of Eurasia, but was decimated by hunting by the early 20th century. In Europe, beavers were reduced to fragmented populations, with combined population numbers being estimated at 1,200 individuals for the [[Rhône]] of France, the [[Elbe]] in Germany, southern Norway, the [[Neman|Neman river]] and [[Dnieper|Dnieper Basin]] in Belarus, and the [[Voronezh (river)|Voronezh river]] in Russia. The beaver has since recolonized parts of its former range, aided by conservation policies and [[Reintroduction of beavers to Europe|reintroductions]]. Beaver populations now range across western, central, and eastern Europe, and [[western Russia]] and the [[Scandinavian Peninsula]].<ref name=iucn-fiber/> Beginning in 2009, beavers have been successfully reintroduced to parts of Great Britain.<ref>{{cite web |title=Beaver reintroduction in the UK |url=https://www.rspb.org.uk/our-work/our-positions-and-casework/our-positions/species/beaver-reintroduction-in-the-uk/ |url-status=live|archive-url=https://web.archive.org/web/20201106144420/https://www.rspb.org.uk/our-work/our-positions-and-casework/our-positions/species/beaver-reintroduction-in-the-uk/ |archive-date=November 6, 2020 |access-date=September 28, 2020 |publisher=[[Royal Society for the Protection of Birds]]}}</ref> {{As of|2020|alt=|pre=In|bare=y}}, the total Eurasian beaver population in Europe was estimated at over one million.<ref>{{cite journal |last=Wróbel |first=M. |year=2020 |title=Population of Eurasian beaver (''Castor fiber'') in Europe |journal=Global Ecology and Conservation |volume=23 |article-number=e01046 |doi=10.1016/j.gecco.2020.e01046|doi-access=free |bibcode=2020GEcoC..2301046W }}</ref> Small native populations are also present in Mongolia and northwestern China; their numbers were estimated at 150 and 700, respectively, {{As of|2016|lc=y}}.<ref name=iucn-fiber/> Under New Zealand's [[Hazardous Substances and New Organisms Act 1996]], beavers are classed as a "prohibited new organism" preventing them from being introduced into the country.<ref>{{cite web |title=Hazardous Substances and New Organisms Act 2003 – Schedule 2 Prohibited new organisms |url=http://legislation.govt.nz/act/public/1996/0030/latest/DLM386556.html#DLM386556 |url-status=live |archive-url=https://web.archive.org/web/20201106092832/http://legislation.govt.nz/act/public/1996/0030/latest/DLM386556.html |archive-date=November 6, 2020 |access-date=January 26, 2012 |publisher=New Zealand Government}}</ref>

==Ecology==
[[File:Europäischer Biber, Elbebiber (Castor fiber albicus).ogv|thumb|alt=A video of beavers swimming and foraging on grasses|Eurasian beavers swimming and foraging.]]

Beavers live in [[freshwater ecosystems]] such as rivers, streams, lakes and ponds. Water is the most important component of beaver habitat; they swim and dive in it, and it provides them refuge from land predators. It also restricts access to their homes and allows them to move building objects more easily. Beavers prefer slower moving streams, typically with a [[Stream gradient|gradient]] (steepness) of one percent, though they have been recorded using streams with gradients as high as 15 percent. Beavers are found in wider streams more often than in narrower ones. They also prefer areas with no regular flooding and may abandon a location for years after a significant flood.{{sfn|Müller-Schwarze|Sun|2003|pp=107, 109}}

Beavers typically select flat landscapes with diverse vegetation close to the water. North American beavers prefer trees being {{cvt|60|m}} or less from the water, but will roam several hundred meters to find more. Beavers have also been recorded in mountainous areas. [[Biological dispersal|Dispersing]] beavers will use certain habitats temporarily before finding their ideal home. These include small streams, temporary swamps, ditches, and backyards. These sites lack important resources, so the animals do not stay there permanently. Beavers have increasingly settled at or near human-made environments, including agricultural areas, [[suburbs]], [[golf courses]], and shopping malls.{{sfn|Müller-Schwarze|Sun|2003|pp=106–110}}

===Food and feeding===
[[File:Beaver Eating Lilly Pads (15682458379).jpg|thumb|alt=Beaver in water eating lily pads|North American beaver eating lily pads.]]

Beavers have an [[herbivorous]] and a [[Generalist and specialist species|generalist]] diet. During the spring and summer, they mainly feed on herbaceous plant material such as leaves, roots, herbs, ferns, grasses, [[sedges]], [[Nymphaea|water lilies]], [[Brasenia|water shield]]s, [[Scirpus|rushes]], and [[Typha|cattails]]. During the fall and winter, they eat more [[Bark (botany)|bark]] and [[cambium]] of woody plants; tree and shrub species consumed include [[aspen]], [[birch]], [[oak]], [[dogwood]], [[willow]] and [[alder]].<ref name="MacDonald"/>{{sfn|Runtz|2015|p=89}}<ref name="canal"/><ref name=JohnHopkins/> There is some disagreement about why beavers select specific woody plants; some research has shown that beavers more frequently select species which are more easily digested,<ref>{{cite journal |last1=Fryxell |first1=J. M. |last2=Doucet |first2=C. M. |year=1993 |title=Diet Choice and the Funcional Response of Beavers |journal=Ecology |volume=74 |issue=5 |pages=1297–1306 |doi=10.2307/1940060 |jstor=1940060 |pmid= |bibcode=1993Ecol...74.1297F |s2cid=}}</ref> while others suggest beavers principally forage based on stem size.<ref>{{cite journal|last1=Mahoney|first1=Michael J.|last2=Stella|first2= John C.|year=2020|title=Stem size selectivity is stronger than species preferences for beaver, a central place forager|journal=[[Forest Ecology and Management]]|volume=475|article-number=118331|doi=10.1016/j.foreco.2020.118331|bibcode=2020ForEM.47518331M |s2cid=224922775}}</ref> Beavers may [[Hoarding (animal behavior)|cache]] their food for the winter, piling wood in the deepest part of their pond where it cannot be reached by other [[Browsing (herbivory)|browsers]]. This cache is known as a "raft"; when the top becomes frozen, it creates a "cap".<ref name=JohnHopkins/><ref name="MacDonald"/> The beaver accesses the raft by swimming under the ice. Many populations of Eurasian beaver do not make rafts, but forage on land during winter.<ref name="MacDonald"/>

===Infrastructure===
{{redirect|Beaver lodge|the town in Alberta, Canada|Beaverlodge}}
{{further|Beaver dam}}
[[File:American Beaver, tree cutting.jpg|thumb|alt=Beaver chewing through a tree trunk|North American beaver chewing down a tree.]]

Beavers need trees and shrubs to use as building material for [[Beaver dam|dams]], which restrict flowing water to create a pond for them to live in, and for lodges, which act as shelters and refuges from predators and the elements. Without such material, or when lodges are not needed, beavers dig [[burrow]]s into a [[Bank (geography)|bank]] to live. Dam construction begins in late summer or early fall, and they repair them whenever needed. Beavers can [[felling|cut down]] trees up to {{cvt|15|cm|0}} wide in less than 50 minutes. Thicker trees, at {{cvt|25|cm|0}} wide or more, may not fall for hours.{{sfn|Müller-Schwarze|Sun|2003|pp=54, 56–57, 68, 108}}<ref>{{cite work|publisher=Oregon Department of Fish and Wildlife |url=https://www.dfw.state.or.us/wildlife/living_with/docs/beaver.pdf|title=Living with Wildlife: American Beaver|accessdate=2025-11-07}}.</ref> When chewing down a tree, beavers switch between biting with the left and right side of the mouth. Tree branches are then cut and carried to their destination with the powerful jaw and neck muscles. Other building materials, like mud and rocks, are held by the forelimbs and tucked between the chin and chest.{{sfn|Runtz|2015|pp=84, 103}}

Beavers start building dams when they hear running water, and the sound of a leak in a dam triggers them to repair it.{{sfn|Runtz|2015|p=104}} To build a dam, beavers stack up relatively long and thick logs between the banks. Heavy rocks keep them stable, and grass is packed between them. Beavers continue to pile on more material until the dam slopes in a direction facing upstream. Dams can range in height from {{cvt|20|cm|0}} to {{cvt|3|m|0}} and can stretch from {{cvt|0.3|m|ft}} to several hundred meters long. Beaver dams are more effective in trapping and slowly leaking water than man-made concrete dams. Lake-dwelling beavers do not need to build dams.{{sfn|Müller-Schwarze|Sun|2003|pp=54–56, 109}}

[[File:Beaverlodge.JPG|thumb|alt=see caption|Open-water beaver lodge in Canada.]]

Beavers make two types of lodges: bank lodges and open-water lodges. Bank lodges are burrows dug along the shore and covered in sticks while the more complex freestanding, open-water lodges are built over a platform of piled-up sticks. The lodge is mostly sealed with mud, except for a hole at the top which acts as an air vent. Both types are accessed by underwater entrances.<ref name=JohnHopkins/>{{sfn|Müller-Schwarze|Sun|2003|pp=56–57}} The above-water space inside the lodge is known as the "living chamber", and a "dining area" may exist close to the water entrance.<ref name="MacDonald"/> Families routinely clean out old plant material and bring in new material.{{sfn|Müller-Schwarze|Sun|2003|p=32}}

North American beavers build more open-water lodges than Eurasian beavers. Beaver lodges built by new settlers are typically small and sloppy. More experienced families can build structures with a height of {{cvt|2|m}} and an above-water diameter of {{cvt|6|m}}. A lodge sturdy enough to withstand the coming winter can be finished in just two nights. Both lodge types can be present at a beaver site. During the summer, beavers tend to use bank lodges to keep cool and use open-water lodges during the winter. The air vent provides ventilation, and newly added carbon dioxide can be cleared in an hour. The lodge remains consistent in oxygen and carbon dioxide levels from season to season.{{sfn|Müller-Schwarze|Sun|2003|pp=6, 57–58}}

Beavers in some areas will dig canals connected to their ponds. The canals fill with groundwater and give beavers access and easier transport of resources, as well as allow them to escape predators. These canals can stretch up to {{cvt|1|m}} wide, {{cvt|0.5|m}} deep, and over {{cvt|0.5|km|1}} long. It has been hypothesized that beavers' canals are not only transportation routes but an extension of their "[[Central place foraging|central place]]" around the lodge and/or food cache.<ref name="canal">{{Cite journal |last1=Abbott|first1=Matthew |last2=Fultz|first2=Brandon|last3=Wilson|first3=Jon|last4=Nicholson|first4=Jody |last5=Black |first5=Matt |last6=Thomas|first6=Adam|last7=Kot|first7=Amanda|last8=Burrows|first8=Mallory |last9=Schaffer |first9=Benton |last10=Benson|first10=David|year=2013|title=Beaver-Dredged Canals and their Spatial Relationship to Beaver-Cut Stumps|volume=121|issue=2|pages=91–96 |journal=Proceedings of the Indiana Academy of Science |url=https://www.researchgate.net/publication/275098832}}</ref><ref>{{Cite journal |last1=Grudzinski |first1=Bartosz P. |last2=Cummins |first2=Hays |last3=Vang|first3=Teng Keng |year=2019|title=Beaver canals and their environmental effects|journal=Progress in Physical Geography: Earth and Environment |pages=189–211 |doi=10.1177/0309133319873116 |volume=44 |issue=2 |s2cid=204257682 |url=https://www.researchgate.net/publication/335838343}}</ref> As they drag wood across the land, beavers leave behind trails or "slides", which they reuse when moving new material.<ref name=JohnHopkins/>

===Environmental effects===
{{main article|Environmental impacts of beavers}}
<!-- Please do not add any more examples to this section. This subject already has its own article -->
{{Multiple image
| header = Beaver dam enlargement
| total_width = 440
| image1 = Beaver dam - geograph.org.uk - 1452003.jpg
| caption1 = September 2009
| image2 = Beaver dam - four months on - geograph.org.uk - 1623430.jpg
| caption2 = December 2009
| footer = Images of a beaver dam over a four-month period. Dams block rivers and create ponds.
| altfooter = Beaver dams being built to block a stream
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The beaver works as an [[ecosystem engineer]] and [[keystone species]], as its activities can have a great impact on the landscape and [[biodiversity]] of an area. Aside from humans, few other extant animals appear to do more to shape their environment.<ref name=Rosell/> When building dams, beavers alter the paths of streams and rivers, allowing for the creation of extensive [[wetland]] habitats.<ref>{{cite journal |author1=Burchsted, D. |author2=Daniels, M. |author3=Thorson, R. |author4=Vokoun, J. |year=2010 |title=The river discontinuum: applying beaver modifications to baseline conditions for restoration of forested headwaters |journal=[[BioScience]] |volume=60 |issue=11 |pages=908–922 |doi=10.1525/bio.2010.60.11.7 |s2cid=10070184 |url=http://opencommons.uconn.edu/cgi/viewcontent.cgi?article=1000&context=geosci |access-date=September 18, 2020 |archive-date=August 5, 2020 |archive-url=https://web.archive.org/web/20200805173711/https://opencommons.uconn.edu/cgi/viewcontent.cgi?article=1000&context=geosci |url-status=live |url-access=subscription }}</ref> In one study, beavers were associated with large increases in open-water areas. When beavers returned to an area, 160% more open water was available during droughts than in previous years, when they were absent.<ref>{{cite journal|last1=Hood|first1=Glynnis A.|last2=Bayley|first2=Suzanne E.|year=2008|title=Beaver (''Castor canadensis'') mitigate the effects of climate on the area of open water in boreal wetlands in western Canada|journal=Biological Conservation|volume=141 |issue=2|pages=556–567 |doi=10.1016/j.biocon.2007.12.003|bibcode=2008BCons.141..556H |s2cid=84584842 }}</ref> Beaver dams also lead to higher [[water table]]s in mineral soil environments and in wetlands such as [[Fen|peatlands]]. In peatlands particularly, their dams stabilize the constantly changing water levels, leading to greater [[Carbon sequestration|carbon storage]].<ref>{{Cite journal|last1=Karran|first1=Daniel J.|last2=Westbrook|first2=Cherie J.|last3=Bedard-Haughn|first3=Angela|date=2018|title=Beaver-mediated water table dynamics in a Rocky Mountain fen|journal=Ecohydrology|language=en|volume=11|issue=2|article-number=e1923|doi=10.1002/eco.1923|bibcode=2018Ecohy..11E1923K |s2cid=133775598|issn=1936-0592}}</ref>

Beaver ponds, and the wetlands that succeed them, remove sediments and pollutants from waterways, and can stop the loss of important soils.<ref>{{cite journal |title=Beaver pond biogeochemical effects in the Maryland Coastal Plain |journal=Biogeochemistry |year=2000 |pages=217–239 |jstor=1469618 |last1=Correll|first1=David L.  |last2= Jordan|first2=Thomas E. |last3= Weller|first3=Donald E. |volume=49 |issue=3 |doi=10.1023/a:1006330501887|s2cid=9393979 }}</ref><ref>{{cite journal|last1=Puttock|first1=A.|last2=Graham|first2=H. A.|last3=Carless|first3=D.|last4=Brazier|first4=R. E.|year=2018|title=Sediment and Nutrient Storage in a Beaver Engineered Wetland|journal=[[Earth Surface Processes and Landforms]]|volume=43|issue=11|pages=2358–2370|doi=10.1002/esp.4398|pmid=30333676|pmc=6175133|bibcode=2018ESPL...43.2358P|doi-access=free}}</ref> These ponds can increase the [[Productivity (ecology)|productivity]] of freshwater ecosystems by accumulating [[nitrogen]] in sediments.<ref name=Rosell/> Beaver activity can affect the temperature of the water; in northern latitudes, ice thaws earlier in the warmer beaver-dammed waters.<ref name=ice>{{cite journal |title=Beavers (''Castor canadensis'') facilitate early access by Canada geese (''Branta canadensis'') to nesting habitat and areas of open water in Canada's boreal wetlands |journal=Mammalian Biology |year=2013 |volume=78 |pages=73–77 |author=Bromley, Chantal K. |author2= Hood, Glynnis A. |issue=1 |doi=10.1016/j.mambio.2012.02.009|bibcode=2013MamBi..78...73B }}</ref> Beavers may contribute to [[climate change]]. In Arctic areas, the floods they create can cause [[permafrost]] to thaw, [[Arctic methane emissions|releasing methane into the atmosphere]].<ref>{{cite journal|last1=Jones|first1=B. M.|last2=Tape|first2=K. D.|last3=Clark |first3=J. A.|last4=Nitze|first4=I. |last5=Grosse|first5=G.|last6=Disbrow|first6=J. |year=2020 |title=Increase in beaver dams controls surface water and thermokarst dynamics in an Arctic tundra region, Baldwin Peninsula, northwestern Alaska |journal=[[Environmental Research Letters]] |volume=15|issue=7 |page=075005|doi=10.1088/1748-9326/ab80f1|bibcode=2020ERL....15g5005J|doi-access=free}}</ref><ref>{{cite web|author=Hunt, Kate|date=June 30, 2020|title=Beavers are gnawing away at the Arctic permafrost, and that's bad for the planet|work=CNN|access-date=March 11, 2021|url=https://www.cnn.com/2020/06/29/americas/beavers-arctic-scn-climate-change-trnd/index.html|archive-date=June 2, 2023|archive-url=https://web.archive.org/web/20230602042218/https://www.cnn.com/2020/06/29/americas/beavers-arctic-scn-climate-change-trnd/index.html|url-status=live}}</ref>

As wetlands are formed and [[riparian]] habitats are enlarged, aquatic plants colonize the newly available watery habitat.<ref name=Rosell/> One study in the [[Adirondacks]] found that beaver engineering lead to an increase of more than 33 percent in [[herbaceous plant]] diversity along the water's edge.<ref>{{cite journal |author1=Wright, J. P. |author2=Jones, C. G. |author3=Flecker, A. S. | year=2002 | title=An ecosystem engineer, the beaver, increases species richness at the landscape scale | journal=[[Oecologia]] | volume=132 | issue=1 | pages=96–101 | doi=10.1007/s00442-002-0929-1 |pmid=28547281 | url=http://www.caryinstitute.org/sites/default/files/public/reprints/Wright_et_al_2002_An_ecosystem_Oecologia_132_96-101.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.caryinstitute.org/sites/default/files/public/reprints/Wright_et_al_2002_An_ecosystem_Oecologia_132_96-101.pdf |archive-date=2022-10-09 |url-status=live|bibcode=2002Oecol.132...96W |s2cid=5940275 }}</ref> Another study in semiarid [[eastern Oregon]] found that the width of riparian vegetation on stream banks increased several-fold as beaver dams watered previously dry terraces adjacent to the stream.<ref>{{cite journal |doi=10.1002/esp.1553 |title=Geomorphic changes upstream of beaver dams in Bridge Creek, an incised stream channel in the interior Columbia River basin, eastern Oregon |author1=Pollock, Michael M. |author2=Beechie, Timothy J. |author3=Jordan, Chris E.  |name-list-style=amp |journal=[[Earth Surface Processes and Landforms]] |volume=32 |issue=8 |pages=1174–1185 |year=2007 |bibcode=2007ESPL...32.1174P |s2cid=129844314 |doi-access=free }}</ref> Riparian ecosystems in arid areas appear to sustain more plant life when beaver dams are present.<ref>{{cite journal|last1=Fairfax|first1=E.|last2=Small|first2=E. E.|year=2018|title=Using remote sensing to assess the impact of beaver damming on riparian evapotranspiration in an arid landscape|journal= Ecohydrology|volume=11|issue=7|article-number=e1993|doi=10.1002/eco.1993|bibcode=2018Ecohy..11E1993F |s2cid=134994160}}</ref> Beaver ponds act as a refuge for riverbank plants during [[wildfires]], and provide them with enough moisture to resist such fires.<ref name=wildfire>{{cite journal|last1=Fairfax|first1=E|last2=Whittle|first2=A.|year=2020|title=Smokey the Beaver: beaver-dammed riparian corridors stay green during wildfire throughout the western United States|journal=[[Ecological Applications]]|volume=30|issue=8|page=e02225|doi=10.1002/eap.2225|pmid=32881199|doi-access=free|bibcode=2020EcoAp..30E2225F}}</ref> [[Beaver eradication in Tierra del Fuego|Introduced beavers at Tierra del Fuego]] have been responsible for destroying the indigenous forest. Unlike trees in North America, many trees in South America cannot grow back after being cut down.<ref name=nature>{{Cite journal | last1=Choi | first1=C. | title=Tierra del Fuego: The beavers must die | doi=10.1038/453968a | journal=[[Nature (journal)|Nature]] | volume=453 | issue=7198 | page=968 | year=2008 | pmid=18563116| doi-access=free }}</ref><ref>{{cite web|author=Gilliland, H. C.|date=June 25, 2019|title=Invasive beavers are destroying Tierra del Fuego|website=[[National Geographic]]|url=https://www.nationalgeographic.com/animals/2019/07/beaver-overpopulation-tierra-del-fuego/|archive-url=https://web.archive.org/web/20190725134742/https://www.nationalgeographic.com/animals/2019/07/beaver-overpopulation-tierra-del-fuego/|archive-date=July 25, 2019|access-date=December 20, 2020}}</ref>
[[File:Sockeye salmon jumping over beaver dam Lake Aleknagik, AK Kristina Ramstad 1997.jpg|thumb|left|upright|[[Salmon]] (''[[Oncorhynchus nerka]]'') jumping a beaver dam.]]
Beaver activity impacts [[Community (ecology)|communities]] of [[aquatic invertebrate]]s. Damming typically leads to an increase of [[lentic ecosystem|slow or motionless water]] species, like [[dragonflies]], [[oligochaetes]], [[snails]], and [[mussels]]. This is to the detriment of [[Lotic ecosystems|rapid water]] species like [[black flies]], [[stoneflies]], and [[Hydropsychidae|net-spinning caddisflies]].<ref name="Rosell" /><ref>{{cite journal|last1=McDowell|first1=D. M.|last2=Naiman|first2=R. J.|year=1986|journal=Oecologia|title=Structure and function of a benthic invertebrate stream community as influenced by beaver (''Castor canadensis'')|volume=68|issue=4|pages=481–489|doi=10.1007/BF00378759|jstor=4217870|pmid=28311700|bibcode=1986Oecol..68..481M|s2cid=24369386}}</ref><ref>{{cite journal|author=Harthun, M.|year=1999|title=The influence of the European beaver (''Castor fiber albicus'') on the biodiversity (Odonata, Mollusca, Trichoptera, Ephemeroptera, Diptera) of brooks in Hesse (Germany)|journal=Limnologica|volume=29|issue=4|pages=449–464|doi=10.1016/S0075-9511(99)80052-8|doi-access=free}}</ref> Beaver floodings create more dead trees, providing more habitat for terrestrial invertebrates like ''[[Drosophila]]'' flies and [[bark beetles]], which live and breed in dead wood.<ref name="Rosell" /><ref>{{cite journal|author=Spieth, H. T.|year=1979|title=The virilis group of ''Drosophila'' and the beaver ''Castor''|journal=The American Naturalist|volume=114|issue=2|pages=312–316|doi=10.1086/283479|jstor=2460228|s2cid=83673603}}</ref><ref>{{cite journal|author=Saarenmaa, H.|year=1978|title=The occurrence of bark beetles (Col. Scolytidae) in a dead spruce stand flooded by beavers (''Castor canadensis'' Kuhl)|journal=Silva Fennica|pages=201–216|doi=10.14214/sf.a14857|doi-access=free|hdl=10138/14857|hdl-access=free}}</ref> The presence of beavers can increase wild [[salmon]] and [[trout]] populations, and the average size of these fishes. These species use beaver habitats for spawning, overwintering, feeding, and as havens from changes in water flow. The positive effects of beaver dams on fish appear to outweigh the negative effects, such as blocking of migration.<ref>{{cite journal |author1=Kemp, P. S. |author2=Worthington, T. A. |author3=Langford, T. E. L. |author4=Tree, A. R. J. |author5=Gaywood, M. J. | year=2012 | title=Qualitative and quantitative effects of reintroduced beavers on stream fish | journal=Fish and Fisheries | volume=13 | issue=2 |pages=158–181 | doi=10.1111/j.1467-2979.2011.00421.x|bibcode=2012AqFF...13..158K }}</ref> Beaver ponds have been shown to be beneficial to [[frog]] populations by protecting areas for larvae to mature in warm water.<ref>{{cite journal|last1=Stevens|first1=C. E.|last2=Paszkowsk|first2=C. A.|last3=Foote|first3=A. L.|year=2007|title=Beaver (''Castor canadensis'') as a surrogate species for conserving anuran amphibians on boreal streams in Alberta, Canada|journal=[[Biological Conservation (journal)|Biological Conservation]]|volume=134|issue=1|pages=1–13|doi=10.1016/j.biocon.2006.07.017|bibcode=2007BCons.134....1S |url=https://www.beaverinstitute.org/wp-content/uploads/2017/08/beaver-Castor-canadensis-as-a-surrogate-species-for-amphibian-conservation-2.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.beaverinstitute.org/wp-content/uploads/2017/08/beaver-Castor-canadensis-as-a-surrogate-species-for-amphibian-conservation-2.pdf |archive-date=2022-10-09 |url-status=live}}</ref> The stable waters of beaver ponds also provide ideal habitat for freshwater [[turtles]].<ref>{{cite journal|last1=Russel|first1=K. R.|last2=Moorman|first2=C. E.|last3=Edwards|first3=J. K.|last4=Guynn|first4=D. C.|year=1999|title=Amphibian and reptile communities associated with beaver (''Castor canadenis'') ponds and unimpounded streams in the Piedmont of South Carolina|journal=Journal of Freshwater Ecology|volume=14|issue=2|pages=149–158|doi=10.1080/02705060.1999.9663666|doi-access=free|bibcode=1999JFEco..14..149R }}</ref>

Beavers help [[waterfowl]] by creating increased areas of water. The widening of the [[riparian zone]] associated with beaver dams has been shown to increase the abundance and diversity of birds favoring the water's edge, an impact that may be especially important in [[semi-arid climate]]s.<ref>{{cite journal |title=Influence of Beaver Dam Density on Riparian Areas and Riparian Birds in Shrubsteepe of Wyoming |journal=[[Western North American Naturalist]] |year=2008 |volume=68 |issue=3 |pages=365–373 |author1=Cooke, Hilary A. |author2=Zack, Steve |doi=10.3398/1527-0904(2008)68[365:IOBDDO]2.0.CO;2 |s2cid=62833818 |url=https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2138&context=wnan |access-date=September 18, 2020 |archive-date=September 22, 2020 |archive-url=https://web.archive.org/web/20200922141102/https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2138&context=wnan |url-status=live |url-access=subscription }}</ref> Fish-eating birds use beaver ponds for foraging, and in some areas, certain species appear more frequently at sites where beavers were active than at sites with no beaver activity.<ref name=Rosell>{{cite journal |title=Ecological impact of beavers ''Castor fiber'' and ''Castor canadensis'' and their ability to modify ecosystems |author=Rosell F|author2= Bozser O|author3= Collen P|author4= Parker H |journal=[[Mammal Review]] |year=2005 |pages=248–276 |url=https://www.researchgate.net/publication/37687178|doi=10.1111/j.1365-2907.2005.00067.x |volume=35 |issue=3–4 |hdl=11250/2438080|hdl-access=free }}</ref><ref name=birds>{{cite journal |title=Bird species richness within beaver ponds in south-central New York |author=Grover, A. M. |author2= Baldassarre, G. A. |year=1995 |journal=Wetlands |pages=108–118|doi=10.1007/BF03160664 |volume=15 |issue=2|bibcode=1995Wetl...15..108G |s2cid=13053029 }}</ref><ref>{{cite journal|last1=Nummbi|first1=P.|last2=Holopainen|first2=S.|year=2014|title=Whole-community facilitation by beaver: ecosystem engineer increases waterbird diversity|journal=[[Aquatic Conservation: Marine and Freshwater Ecosystems]]|volume=24|issue=5|pages=623–633|doi=10.1002/aqc.2437|bibcode=2014ACMFE..24..623N }}</ref> In a study of [[Wyoming]] streams and rivers, watercourses with beavers had 75 times as many [[ducks]] as those without.<ref>{{cite journal |title=The Importance of Beavers to Waterfowl and Wetlands Habitats in Wyoming |author=McKinstry, M. C.|author2= Caffrey, P. |author3= Anderson, S. H. |journal=[[Journal of the American Water Resources Association]] |year=2001|doi=10.1111/j.1752-1688.2001.tb03660.x |volume=37 |issue=6 |pages=1571–1577|bibcode=2001JAWRA..37.1571M|s2cid=128410215}}</ref> As trees are drowned by rising beaver impoundments, they become an ideal habitat for [[woodpeckers]], which carve cavities that may be later used by other bird species.<ref name=Rosell/><ref name=birds/> Beaver-caused ice thawing in northern latitudes allows [[Canada geese]] to nest earlier.<ref name=ice/>

Other semi-aquatic mammals, such as [[European water vole|water voles]], [[muskrats]], [[minks]], and [[otters]], will shelter in beaver lodges.<ref name=Rosell/> Beaver modifications to streams in Poland create habitats favorable to [[bat]] species that forage at the water surface and "prefer moderate vegetation clutter".<ref>{{cite journal|last1=Ciechanowski|first1=M.|last2=Kubic|first2=W.|last3=Rynkiewicz|first3=A.|last4=Zwolicki|first4=A.|year=2011|title=Reintroduction of beavers ''Castor fiber'' may improve habitat quality for vespertilionid bats foraging in small river valleys|journal=European Journal of Wildlife Research|volume=57|issue=4|pages=737–747|doi=10.1007/s10344-010-0481-y|doi-access=free}}</ref> Large herbivores, such as some [[deer]] species, benefit from beaver activity as they can access vegetation from fallen trees and ponds.<ref name=Rosell/>

===Mortality and health===
Beavers usually live up to 10 years. [[Felid]]s, [[canid]]s, and [[bears]] may prey upon them. Beavers are protected from predators when in their lodges, and prefer to stay near water. Parasites of the beaver include the bacteria ''[[Francisella tularensis]]'', which causes [[tularemia]]; the protozoan ''[[Giardia duodenalis]]'', which causes [[giardiasis]] (beaver fever); and the [[beaver beetle]] and [[mites]] of the genus ''[[Schizocarpus]]''.{{sfn|Müller-Schwarze|Sun|2003|pp=83, 113–114, 118–122}}<ref name="beaverfever"/> They have also been recorded to be infected with the [[rabies virus]].<ref>{{cite journal|last1=Morgan|first1=S. M. D.|last2=Pouliott|first2=C. E.|last3=Rudd|first3=R. J.|last4=Davis|first4=A. D.|year=2015|title=Antigen Detection, Rabies Virus Isolation, and Q-PCR in the Quantification of Viral Load in a Natural Infection of the North American Beaver (''Castor canadensis'')|journal=[[Journal of Wildlife Diseases]]|volume=51|issue=1|pages=287–289|doi=10.7589/2014-05-120|pmid=25380356|s2cid=5364807}}</ref>

==Behavior==
{{multiple image
| width             = 220
| direction         = vertical
| image1            = Beaver family upper Los Gatos Creek 2008 Mercury Freedom.jpg
| caption1          = North American beaver family, with the center pair grooming one another.
| image2            = Tayside Beaver mother and kit June 5, 2010 Ray Scott.jpg
| caption2          = Eurasian beaver parent and kit.
}}

Beavers are mainly [[nocturnality|nocturnal]] and [[Crepuscular animal|crepuscular]], and spend the daytime in their shelters. In northern latitudes, beaver activity is decoupled from the [[Circadian rhythm|24-hour cycle]] during the winter, and may last as long as 29 hours. They do not [[hibernate]] during winter, and spend much of their time in their lodges.<ref name="MacDonald"/><ref name=JohnHopkins/>{{sfn|Runtz|2015|p=76}}

===Family life===
The core of beaver social organization is the family, which is composed of an adult male and an adult female in a [[Pair bond|monogamous pair]] and their offspring.<ref name="MacDonald"/><ref name=Pelagic/> Beaver families can have as many as ten members; groups about this size require multiple lodges.{{sfn|Müller-Schwarze|Sun|2003|pp=30–31}} [[Mutual grooming]] and play fighting maintain bonds between family members, and aggression between them is uncommon.<ref name=Pelagic/>

Adult beavers mate with their partners, though partner replacement appears to be common. A beaver that loses its partner will wait for another one to come by. [[Estrus]] cycles begin in late December and peak in mid-January. Females may have two to four estrus cycles per season, each lasting 12–24 hours. The pair typically mate in the water and to a lesser extent in the lodge, for half a minute to three minutes.{{sfn|Müller-Schwarze|Sun|2003|pp=80, 85}}

Up to four young, or kits, are born in spring and summer, after a three or four-month [[gestation]].<ref name="Pelagic" />{{sfn|Müller-Schwarze|Sun|2003|p=80}} Newborn beavers are [[precocial]] with a full fur coat, and can open their eyes within days of birth.<ref name="JohnHopkins" /><ref name="Pelagic" /> Their mother is the primary caretaker, while their father maintains the territory.<ref name="MacDonald" /> Older siblings from a previous litter also play a role.{{sfn|Müller-Schwarze|Sun|2003|pp=32–33}}

After they are born, the kits spend their first one to two months in the lodge. Kits suckle for as long as three months, but can eat solid food within their second week and rely on their parents and older siblings to bring it to them. Eventually, beaver kits explore outside the lodge and forage on their own, but may follow an older relative and hold onto their backs.<ref name="Pelagic" /> After their first year, young beavers help their families with construction.<ref name="MacDonald" /> Beavers sexually mature around 1.5–3 years.<ref name="JohnHopkins" /> They become independent at two years old, but remain with their parents for an extra year or more during times of food shortage, high population density, or drought.{{sfn|Müller-Schwarze|Sun|2003|pp=332–333, 100–101}}<ref>{{cite journal|last1=Mayer|first1=M|last2=Zedrosser|first2=A|last3=Rosell|first3=F|year=2017|title=When to leave: the timing of natal dispersal in a large, monogamous rodent, the Eurasian beaver|journal=Animal Behaviour|volume=123|pages=375–382|doi=10.1016/j.anbehav.2016.11.020|s2cid=53183887}}</ref>

===Territories and spacing===
[[File:Castor fiber vistulanus2.jpg|thumb|left|alt=A beaver on a water bank|[[Eurasian beaver]] near its dam.]]
Beavers typically disperse from their parental colonies during the spring or when the winter snow melts. They often travel less than {{convert|5|km|mi|0|abbr=on}}, but long-distance dispersals are not uncommon when previous colonizers have already exploited local resources. Beavers are able to travel greater distances when free-flowing water is available. Individuals may meet their mates during the dispersal stage, and the pair travel together. It may take them weeks or months to reach their final destination; longer distances may require several years.{{sfn|Müller-Schwarze|Sun|2003|pp=101–103}}<ref>{{cite journal|last1=McNew|first1=L. B.|last2=Woolf|first2=A.|year=2005|title=Dispersal and Survival of Juvenile Beavers (''Castor canadensis'') in Southern Illinois|journal=The American Midland Naturalist|volume=154|issue=1|pages=217–228|doi=10.1674/0003-0031(2005)154[0217:DASOJB]2.0.CO;2|jstor=3566630|s2cid=86432359 }}</ref> Beavers establish and defend [[Territory (animal)|territories]] along the banks of their ponds, which may be {{convert|1|–|7|km|1|abbr=on}} in length.<ref>{{cite journal|last1=Graf|first1=P. M.|last2=Mayer|first2=M.|last3=Zedrosser|first3=A.|last4=Hackländer|first4=K.|last5=Rosell|first5=F.|year=2016|title=Territory size and age explain movement patterns in the Eurasian beaver|journal=Mammalian Biology – Zeitschrift für Säugetierkunde|volume=81|issue=6|pages=587–594|doi=10.1016/j.mambio.2016.07.046|bibcode=2016MamBi..81..587G }}</ref>

Beavers mark their territories by constructing scent mounds made of mud and vegetation, scented with castoreum.{{sfn|Runtz|2015|p=128}} Those with many territorial neighbors create more scent mounds. Scent marking increases in spring, during the dispersal of yearlings, to deter interlopers.<ref name="Rosell 1997">{{cite journal | last1=Rosell | first1=Frank | last2=Nolet | first2=Bart A. | year=1997 | title=Factors Affecting Scent-Marking Behavior in Eurasian Beaver (''Castor fiber'') | journal=[[Journal of Chemical Ecology]] | volume=23 | issue=3 | pages=673–689 | doi=10.1023/B:JOEC.0000006403.74674.8a | bibcode=1997JCEco..23..673R | hdl=11250/2438031 | s2cid=31782872 | hdl-access=free }}</ref> Beavers are generally intolerant of intruders and fights may result in deep bites to the sides, rump, and tail.<ref name=Pelagic/> They exhibit a behavior known as the "[[dear enemy effect]]"; a territory-holder will investigate and become familiar with the scents of its neighbors and react more aggressively to the scents of strangers passing by.<ref name="Bjorkoyli 2002">{{cite journal|last1=Bjorkoyli|first1=Tore|last2=Rosell|first2=Frank|year=2002|title=A Test of the Dear Enemy Phenomenon in the Eurasian Beaver|journal=[[Animal Behaviour (journal)|Animal Behaviour]]|volume=63|issue=6|pages=1073–1078|doi=10.1006/anbe.2002.3010|hdl=11250/2437993|s2cid=53160345|hdl-access=free}}</ref> Beavers are also more tolerant of individuals that are their kin. They recognize them by using their keen sense of smell to detect differences in the composition of anal gland secretions. Anal gland secretion profiles are more similar among relatives than unrelated individuals.<ref name= "Lixing 1998">{{cite journal | last1=Sun | first1=Lixing | last2=Muller-Schwarze | first2=Dietland | year=1998 | title=Anal Gland Secretion Codes for Relatedness in the Beaver, ''Castor canadensis'' | journal=[[Ethology (journal)|Ethology]] | volume=104 | issue=11| pages=917–927 | doi=10.1111/j.1439-0310.1998.tb00041.x| bibcode=1998Ethol.104..917S }}</ref><ref>{{cite journal|last1=Sun | first1=Lixing | last2=Muller-Schwarze | first2=Dietland |year=1997|title=Sibling recognition in the beaver: A field test for phenotype matching|journal=Animal Behaviour|volume=54|issue=3|pages=493–502|doi=10.1006/anbe.1996.0440| pmid=9299035 | s2cid=33128765 }}</ref>

===Communication===
Beavers within a family greet each other with whines. Kits will attract the attention of adults with mews, squeaks, and cries. Defensive beavers produce a hissing growl and gnash their teeth.<ref name=Pelagic/> Tail slaps, which involve an animal hitting the water surface with its tail, serve as alarm signals warning other beavers of a potential threat. An adult's tail slap is more successful in alerting others, who will escape into the lodge or deeper water. Juveniles have not yet learned the proper use of a tail slap, and hence are normally ignored.{{sfn|Runtz|2015|pp=55–57}}{{sfn|Müller-Schwarze|Sun|2003|pp=48–49}} Eurasian beavers have been recorded using a territorial "stick display", which involves individuals holding up a stick and bouncing in shallow water.{{sfn|Runtz|2015|p=133}}

==Interactions with humans==
[[File:Grey owl feeding beaver a jelly roll.jpg|right|thumb|[[Grey Owl]] feeding his beaver.|alt=Black and white photo of a man feeding a beaver]]
Beavers sometimes come into conflict with humans over land use; individual beavers may be labeled as "nuisance beavers". Beavers can damage crops, timber stocks, roads, ditches, gardens, and pastures via gnawing, eating, digging, and flooding.<ref name=JohnHopkins/> They occasionally [[Beaver attack|attack]] humans and domestic pets, particularly when infected with [[rabies]], in defense of their territory, or when they feel threatened.<ref name="LSM-2016">{{cite news |last1=Андреев |first1=Александр |last2=Eng.LSM.lv |title=Diabolical beaver holds Daugavpils in its thrall |url=https://eng.lsm.lv/article/society/society/diabolical-beaver-holds-daugavpils-in-its-thrall.a179291/ |access-date=29 October 2022 |work=eng.lsm.lv |publisher=[[Public Broadcasting of Latvia]] |date=21 April 2016 |archive-date=October 30, 2022 |archive-url=https://web.archive.org/web/20221030161519/https://eng.lsm.lv/article/society/society/diabolical-beaver-holds-daugavpils-in-its-thrall.a179291/ |url-status=live }}</ref> Some of these attacks have been fatal, including at least one human death.<ref name="guardian">{{cite web|date=May 29, 2013|title=Beaver kills man in Belarus|url=https://www.theguardian.com/world/2013/may/29/beaver-kills-man-belarus|url-status=live|archive-url=https://web.archive.org/web/20201108130526/http://www.theguardian.com/world/2013/may/29/beaver-kills-man-belarus|archive-date=November 8, 2020|access-date=November 11, 2020|work=[[The Guardian]]|agency=Associated Press}}</ref><ref name="huget">{{cite news|author=Huget, Jennifer LaRue|date=September 6, 2012|title=Beavers and rabies|newspaper=[[The Washington Post]]|url=https://www.washingtonpost.com/blogs/the-checkup/post/beavers-and-rabies-whats-up-with-that/2012/09/06/5a0f2f12-f86a-11e1-a93b-7185e3f88849_blog.html|url-status=live|access-date=October 20, 2020|archive-url=https://web.archive.org/web/20201023024353/https://www.washingtonpost.com/blogs/the-checkup/post/beavers-and-rabies-whats-up-with-that/2012/09/06/5a0f2f12-f86a-11e1-a93b-7185e3f88849_blog.html|archive-date=October 23, 2020}}</ref><ref>{{cite news|url=http://www.adn.com/article/20110611/beavers-get-tough-defending-their-turf|title=Beavers get tough defending their turf|author=Shinohara, Rosemary|date=June 11, 2011|work=[[Alaska Dispatch News]]|access-date=October 20, 2020|archive-date=July 11, 2024|archive-url=https://web.archive.org/web/20240711080833/https://www.adn.com/alaska-news/article/beavers-get-tough-defending-their-turf/2011/06/12/|url-status=live}}</ref> Beavers can spread [[giardiasis]] ('beaver fever') by infecting surface waters,<ref name="beaverfever">{{cite journal|last1=Tsui|first1=C. K-M.|last2=Miller|first2=R.|last3=Uyaguari-Diaz|first3=M.|last4=Tang|first4=P.|last5=Chauve|first5=C.|last6=Hsiao|first6=W.|last7=Isaac-Renton|first7=J.|last8=Prystajecky|first8=N.|year=2018|title=Beaver Fever: Whole-Genome Characterization of Waterborne Outbreak and Sporadic Isolates To Study the Zoonotic Transmission of Giardiasis|journal= mSphere|volume=3|issue=2|article-number=e00090-18 |doi=10.1128/mSphere.00090-18|doi-access=free|pmid= 29695621|pmc= 5917422}}</ref> though outbreaks are more commonly caused by human activity.{{sfn|Müller-Schwarze|Sun|2003|p=121}}

[[Flow devices]], like [[beaver pipes]], are used to manage beaver flooding, while fencing and hardware cloth protect trees and shrubs from beaver damage. If necessary, hand tools, heavy equipment, or explosives are used to remove dams.<ref>{{cite journal |title=Best Management Solutions for Beaver Problems |author=Callahan, M. |journal=Association of Massachusetts Wetland Scientists |date=April 2005 |pages=12–14|url=https://www.beaversolutions.com/wp-content/uploads/2018/04/amwx-Apr-05.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.beaversolutions.com/wp-content/uploads/2018/04/amwx-Apr-05.pdf |archive-date=2022-10-09 |url-status=live}}</ref><ref>{{cite web|title=Beaver Damage Management|url=http://agrilife.org/txwildlifeservices/files/2016/07/fs_beaver.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://agrilife.org/txwildlifeservices/files/2016/07/fs_beaver.pdf |archive-date=2022-10-09 |url-status=live|date=January 2011|website=US Department of Agriculture|access-date=December 23, 2020}}</ref> Hunting, [[trapping]], and relocation may be permitted as forms of population control and for removal of individuals.<ref name=JohnHopkins/> The governments of Argentina and Chile have authorized the trapping of invasive beavers in hopes of eliminating them.<ref name=nature/> The ecological importance of beavers has led to cities like [[Seattle]] designing their parks and [[Urban green space|green spaces]] to accommodate the animals.<ref name="Bailey">{{cite journal|last1=Bailey|first1=D. R.|last2=Dittbrenner|first2=B. J.|last3=Yocom|first3=K. P.|year=2018|title=Reintegrating the North American beaver (''Castor canadensis'') in the urban landscape|journal=WIREs Water|volume=6|issue=1|article-number=e1323|doi=10.1002/wat2.1323|s2cid=85513383|url=https://www.martinezbeavers.org/wordpress/wp-content/uploads/2018/10/Reintegrating_the_North_American_beaver-002-1.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.martinezbeavers.org/wordpress/wp-content/uploads/2018/10/Reintegrating_the_North_American_beaver-002-1.pdf |archive-date=2022-10-09 |url-status=live}}</ref> The [[Martinez beavers]] became famous in the mid-2000s for their role in improving the ecosystem of [[Alhambra Creek]] in [[Martinez, California]].<ref>{{cite book|author=L. Riley|first=Ann|title=Restoring Neighborhood Streams – Planning, Design, and Construction|publisher=Island Press|year=2016|isbn=978-1-61091-740-7|location=Washington, DC|pages=177–178}}</ref>

Zoos have displayed beavers since at least the 19th century, though not commonly. In captivity, beavers have been used for entertainment, fur harvesting, and for reintroduction into the wild. Captive beavers require access to water, substrate for digging, and artificial shelters.<ref>{{cite journal|last1=Campbell-Palmer|first1=R.|last2=Rosell|first2=F.|year=2015|title=Captive Care and Welfare Considerations for Beavers|journal=Zoo Biology|volume=34|issue=2|pages=101–109|doi=10.1002/zoo.21200|pmid=25653085|doi-access=free|hdl=11250/2437934|hdl-access=free}}</ref> [[Grey Owl|Archibald Stansfeld "Grey Owl" Belaney]] pioneered beaver conservation in the early 20th century. Belaney wrote several books, and was first to professionally film beavers in their environment. In 1931, he moved to a log cabin in [[Prince Albert National Park]], where he was the "caretaker of park animals" and raised a beaver pair and their four offspring.{{sfn|Backhouse|2015|pp=64, 68–71}} [[Dorothy Burney Richards]], inspired by Belaney, lived with beavers in her home at [[Beaversprite]].<ref name="bio">{{Cite journal |date=2001 |title=Dorothy B(urney) Richards |url=https://go.gale.com/ps/retrieve.do?tabID=Biographies&resultListType=RESULT_LIST&searchResultsType=MultiTab&hitCount=1&searchType=PersonSearchForm&currentPosition=1&docId=GALE%7CH1000082590&docType=Biography&sort=Relevance&contentSegment=ZXAM-MOD1&prodId=BIC&pageNum=1&contentSet=GALE%7CH1000082590&searchId=R3&userGroupName=wikipedia&inPS=true |publisher=Gale |journal=Gale Literature: Contemporary Authors |access-date=2022-04-17 |archive-date=2022-04-18 |archive-url=https://web.archive.org/web/20220418222747/https://galeapps.gale.com/apps/auth?userGroupName=wikipedia&origURL=https%3A%2F%2Fgo.gale.com%2Fps%2Fretrieve.do%3FtabID%3DBiographies%26resultListType%3DRESULT_LIST%26searchResultsType%3DMultiTab%26hitCount%3D1%26searchType%3DPersonSearchForm%26currentPosition%3D1%26docId%3DGALE%257CH1000082590%26docType%3DBiography%26sort%3DRelevance%26contentSegment%3DZXAM-MOD1%26prodId%3DBIC%26pageNum%3D1%26contentSet%3DGALE%257CH1000082590%26searchId%3DR3%26userGroupName%3Dwikipedia%26inPS%3Dtrue&prodId=BIC |url-status=live }}</ref>

===Commercial use===
{{multiple image
| width             = 220
| direction         = vertical
| image1            = Beaverbollocks.jpg
| alt1              = see caption
| caption1          = Depiction of a beaver hunt from a medieval [[bestiary]] with the beaver depicted as biting off its testicles.
| image2            = BeaverPelt (5118396762).jpg
| alt2              = A beaver pelt
| caption2          = Beaver pelts were the driving force of the [[North American fur trade]].
}}

Beavers have been hunted, trapped, and exploited for their fur, meat, and castoreum. Since the animals typically stayed in one place, trappers could easily find them and could kill entire families in a lodge.{{sfn|Poliquin|2015|p=89}} Many pre-modern people mistakenly thought that castoreum was produced by the testicles or that the castor sacs of the beaver were its testicles, and females were [[hermaphrodite]]s. [[Aesop's Fables]] describes beavers chewing off their testicles to preserve themselves from hunters, which is impossible because a beaver's testicles are internal. This myth persisted for centuries, and was corrected by French physician [[Guillaume Rondelet]] in the 1500s.{{sfn|Backhouse|2015|p=98}}{{sfn|Poliquin|2015|pp=55, 58–62, 65}} Beavers have historically been hunted and captured using [[Deadfall trap|deadfalls]], [[Snare trap|snares]], nets, bows and arrows, spears, clubs, firearms, and leg-hold traps. Castoreum was used to lure the animals.<ref name=CIPNE/>{{sfn|Müller-Schwarze|Sun|2003|pp=150–151}}

Castoreum was used for a variety of medical purposes; [[Pliny the Elder]] promoted it as a treatment for stomach problems, flatulence, seizures, [[sciatica]], [[vertigo]], and [[epilepsy]]. He stated it could stop hiccups when mixed with vinegar, toothaches if mixed with oil (by administering into the ear opening on the same side as the tooth), and could be used as an [[antivenom]]. The substance has traditionally been prescribed to treat [[hysteria]] in women, which was believed to have been caused by a "toxic" womb.{{sfn|Poliquin|2015|pp=74, 76}} Castoreum's properties have been credited to the accumulation of [[salicylic acid]] from willow and aspen trees in the beaver's diet, and has a physiological effect comparable to [[aspirin]].<ref name="MacDonald"/>{{sfn|Backhouse|2015|pp=97–98}} Today, the medical use of castoreum has declined and is limited mainly to [[homeopathy]].<ref name="MacDonald"/> The substance is also used as an ingredient in perfumes and [[tincture]]s, and as a flavouring in food and drinks.<ref name="MacDonald"/>{{sfn|Poliquin|2015|p=74}}

Various [[Indigenous peoples of the Americas|Native American]] groups have historically hunted beavers for food,<ref name="CIPNE">{{cite web |last1=Kuhnlein |first1=H. V. |author-link=Harriet V. Kuhnlein |last2=Humphries |first2=M. H. |title=Beaver |url=http://traditionalanimalfoods.org/mammals/furbearers/page.aspx?id=6142 |access-date=December 20, 2020 |website=Centre for Indigenous Peoples' Nutrition and Environment |archive-date=October 3, 2020 |archive-url=https://web.archive.org/web/20201003121130/http://traditionalanimalfoods.org/mammals/furbearers/page.aspx?id=6142 |url-status=live }}</ref> they preferred its meat more than other [[red meats]] because of its higher calorie and fat content, and the animals remained plump in winter when they were most hunted. The bones were used to make tools.{{sfn|Backhouse|2015|p=56}}<ref name=CIPNE/> In medieval Europe, the Catholic Church considered the beaver to be part mammal and part fish, and allowed followers to eat the scaly, fishlike tail on meatless Fridays during [[Lent]]. Beaver tails were thus highly prized in Europe; they were described by French naturalist [[Pierre Belon]] as tasting like a "nicely dressed eel".{{sfn|Poliquin|2015|p=24}}

Beaver pelts were used to make [[Beaver hat|hat]]s; [[felting|felters]] would remove the guard hairs. The number of pelts needed depended on the type of hat, with [[Cavalier hat|Cavalier]] and [[Capotain|Puritan]] hats requiring more fur than [[top hat]]s.{{sfn|Backhouse|2015|pp=99–101}} In the late 16th century, Europeans began to [[North American fur trade|deal in North American furs]] due to the lack of taxes or tariffs on the continent and the decline of fur-bearers at home. Beaver pelts caused or contributed to the [[Beaver Wars]], [[King William's War]], and the [[French and Indian War]]; the trade made [[John Jacob Astor]] and the owners of the [[North West Company]] very wealthy. For Europeans in North America, the fur trade was a driver of the exploration and westward exploration on the continent and contact with native peoples, who traded with them.{{sfn|Poliquin|2015|pp=92–94}}<ref>{{cite book|last=Madsen|first=Axl|title=John Jacob Astor: America's First Multimillionaire|date=January 30, 2001 |pages=2, 4, 49, 226–231|publisher=Wiley |isbn=978-0-471-38503-5}}</ref><ref>{{Cite book |title=The Canadian Prairies |last=Friesen |first=Gerald |publisher=University of Toronto Press |year=1987 |isbn=0-8020-6648-8 |url=https://books.google.com/books?id=SIMHAcD8LNkC&pg=PA62 |page=62 |access-date=April 7, 2023 |archive-date=April 23, 2023 |archive-url=https://web.archive.org/web/20230423112208/https://books.google.com/books?id=SIMHAcD8LNkC&pg=PA62 |url-status=live }}</ref> The fur trade peaked between 1860 and 1870, when over 150,000 beaver pelts were purchased annually by the [[Hudson's Bay Company]] and fur companies in the United States.{{sfn|Müller-Schwarze|Sun|2003|p=98}} The contemporary global fur trade is not as profitable due to conservation, [[Fur clothing#Anti-fur campaigns|anti-fur]] and [[animal rights]] campaigns.<ref name="MacDonald"/>{{sfn|Müller-Schwarze|Sun|2003|pp=150–151}}

===In culture===

[[File:Beaver sculpture, Centre Block.jpg|thumb|left|alt=Stone sculpture of a beaver over an entrance to the Parliament Building of Canada|Beaver sculpture over entrance to the [[Canadian Parliament Buildings|Canadian Parliament Building]].]]

The beaver has been used to represent productivity, trade, tradition, masculinity, and respectability. References to the beaver's skills are reflected in everyday language. The English verb "to beaver" means working with great effort and being "as busy as a beaver"; a "beaver intellect" refers to a way of thinking that is slow and honest. Though it typically has a wholesome image, the beaver's name has been used as a [[sexual slang|sexual term]] for the human [[vulva]].{{sfn|Poliquin|2015|pp=209–210}}<ref name="Francis"/>

[[Mythologies of the indigenous peoples of the Americas|Native American myths]] emphasize the beaver's skill and industriousness. In the mythology of the [[Haida people|Haida]], beavers are descended from the Beaver-Woman, who built a dam on a stream next to their cabin while her husband was out hunting and gave birth to the first beavers. In a [[Cree]] story, the Great Beaver and its dam caused a [[Flood myth|world flood]]. Other tales involve beavers using their tree chewing skills against an enemy.{{sfn|Poliquin|2015|pp=14–15, 130–131}} Beavers have been featured as companions in some stories, including a [[Lakota people|Lakota]] tale where a young woman flees from her evil husband with the aid of her pet beaver.{{sfn|Backhouse|2015|p=75}}

Europeans have traditionally thought of beavers as fantastical animals due to their amphibious nature. They depicted them with exaggerated tusk-like teeth, dog- or pig-like bodies, fish tails, and visible testicles. French cartographer [[Nicolas de Fer]] illustrated beavers building a dam at [[Niagara Falls]], fantastically depicting them like human builders. Beavers have also appeared in literature such as [[Dante Alighieri|Dante Alighieri's]] ''[[Divine Comedy]]'' and the writings of [[Athanasius Kircher]], who wrote that on [[Noah's Ark]] the beavers were housed near a water-filled tub that was also used by [[mermaid]]s and otters.{{sfn|Poliquin|2015|pp=20–21, 28–32, 134}}

The beaver has long been associated with Canada, appearing on the first pictorial postage stamp issued in the [[British North America|Canadian colonies]] in 1851 as the so-called "[[Postage stamps and postal history of Canada|Three-Penny Beaver]]". It was declared the [[national animal]] in 1975. The [[Nickel (Canadian coin)|five-cent coin]], the coat of arms of the Hudson's Bay Company, and the logos for [[Parks Canada]] and [[Roots Canada]] use its image. [[Frank and Gordon]] are two fictional beavers that appeared in [[Bell Canada|Bell Canada's]] advertisements between 2005 and 2008. However, the beaver's status as a rodent has made it controversial, and it was not chosen to be on the [[Arms of Canada]] in 1921.{{sfn|Backhouse|2015|pp=5–6}}{{sfn|Runtz|2015|pp=2–4}} The beaver has commonly been used to represent Canada in [[political cartoons]], typically to signify it as a friendly but relatively weak nation.<ref name="Francis">{{cite journal|author=Francis, Margot|year=2004|title=The Strange Career of the Canadian Beaver: Anthropomorphic Discourses and Imperial History|journal=[[Journal of Historical Sociology]]|volume=17|issue=2–3|pages=209–239|doi=10.1111/j.1467-6443.2004.00231.x}}</ref> In the United States, the beaver is the [[List of U.S. state animals|state animal]] of [[New York (state)|New York]] and [[Oregon]].{{sfn|Backhouse|2015|p=6}} It is also featured on the coat of arms of the [[London School of Economics]].{{sfn|Runtz|2015|p=2}}<!-- Please do not add any more examples of beavers as mascots or symbols. These examples are mentioned in general sources about the animals. -->

==See also==
* [[Beaver drop]]

==References==

{{Reflist|30em}}

=== Sources ===
{{Refbegin}}
* {{Cite book|last=Backhouse|first=Frances|year=2015|title=Once They Were Hats: In Search of the Mighty Beaver|publisher=[[ECW Press]]|isbn=978-1-77090-755-3|url=https://books.google.com/books?id=wXkuCQAAQBAJ&q=once+they+were+hats|access-date=March 18, 2023|archive-date=April 6, 2023|archive-url=https://web.archive.org/web/20230406145536/https://books.google.com/books?id=wXkuCQAAQBAJ&q=once+they+were+hats|url-status=live}}
* {{Cite book|last1=Müller-Schwarze|first1=Dietland|last2=Sun|first2=Lixing|year=2003|title=The Beaver: Natural History of a Wetlands Engineer|url=https://books.google.com/books?id=eqIenKko3lAC&q=Beaver&pg=PP1|publisher=[[Cornell University Press]]|isbn=978-0-8014-4098-4|access-date=October 15, 2020|archive-date=July 11, 2024|archive-url=https://web.archive.org/web/20240711080832/https://books.google.com/books?id=eqIenKko3lAC&q=Beaver&pg=PP1#v=snippet&q=Beaver&f=false|url-status=live}}
* {{Cite book|last=Poliquin|first=Rachel|year=2015|title=Beaver|publisher=[[Reaktion Books]]|isbn=978-1-78023-456-4|url=https://books.google.com/books?id=DcGkCQAAQBAJ&q=beaver+reaktion|access-date=March 18, 2023|archive-date=July 11, 2024|archive-url=https://web.archive.org/web/20240711080832/https://books.google.com/books?id=DcGkCQAAQBAJ&q=beaver+reaktion#v=snippet&q=beaver%20reaktion&f=false|url-status=live}}
* {{Cite book|last=Runtz|first=Michael|year=2015|title=Dam Builders: The Natural History of Beavers and their Ponds|publisher=[[Fitzhenry & Whiteside]]|isbn=978-1-55455-324-2}}
{{Refend}}

==Further reading==
* {{Cite book|last=Goldfarb|first=Ben|year=2018|title=Eager: The Surprising, Secret Life of Beavers and Why They Matter|publisher=[[Chelsea Green Publishing]]|isbn=978-1-60358-908-6}}

==External links==
{{Wikisource|Portal:Mammals#Beaver|Beaver}}
* [https://www.beaverinstitute.org/ Beaver Institute] Charity that supports beavers
* [http://northernbushcraft.com/animalTracks/beaver/notes.htm Beaver Tracks]: How to identify beaver tracks in the wild

{{Castorimorpha|C.|state=collapsed}}
{{Taxonbar|from=Q47542}}
{{Authority control}}

[[Category:Beavers| ]]
[[Category:Fauna of the Holarctic realm]]
[[Category:Articles containing video clips]]
[[Category:Extant Miocene first appearances]]
[[Category:Animal taxa named by Carl Linnaeus]]
[[Category:Semiaquatic mammals]]