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61-744: 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 capybaras , weighing up to 50 kg (110 lb). They have stout bodies with large heads, long chisel-like incisors , brown or gray fur , hand-like front feet, 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

122-667: A generalist diet. During the spring and summer, they mainly feed on herbaceous plant material such as leaves, roots, herbs, ferns, grasses, sedges , water lilies , water shields , rushes , and cattails . During the fall and winter, they eat more bark and cambium of woody plants; tree and shrub species consumed include aspen , birch , oak , dogwood , willow and alder . 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, while others suggest beavers principally forage based on stem size. Beavers may cache their food for

183-470: A 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. Beavers typically select flat landscapes with diverse vegetation close to the water. North American beavers prefer trees being 60 m (200 ft) or less from

244-415: 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 touch and hearing. Touch is more advanced in the lips and hands than the whiskers and tail. Vision in

305-411: A primate with traits that would represent anything in between humans and the other great apes . If the concept of an ape-man were based on neontology, then our phenotype would resemble Bigfoot . Since the concept was based on paleontology, the idea of an ape-man could possibly be represented by the fossil hominids. Neontology studies extant (living) taxa and recently extinct taxa, but declaring

366-651: 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. Castoroides is estimated to have had a length of 1.9–2.2 m (6.2–7.2 ft) and a weight of 90–125 kg (198–276 lb). Fossils of one genus in Castoroidinae, Dipoides , have been found near piles of chewed wood, though Dipoides appears to have been an inferior woodcutter compared to Castor . Researchers suggest that modern beavers and Castoroidinae shared

427-446: A "prohibited new organism" preventing them from being introduced into the country. 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

488-528: A bark-eating 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. The genus Castor likely originated in Eurasia . The earliest fossil remains appear to be C. neglectus , found in Germany and dated 12–10 mya. Mitochondrial DNA studies place

549-465: 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 blood vessel system which allows the animal to lose heat in warm temperatures and retain heat in cold temperatures. The beaver's sex organs are inside

610-673: A dam, beavers stack up relatively long and thick logs between banks and in opposite directions. 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 20 cm (7.9 in) to 3 m (9.8 ft) and can stretch from 0.3 m (1 ft 0 in) 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. Beavers make two types of lodges: bank lodges and open-water lodges. Bank lodges are burrows dug along

671-1009: A height of 2 m (6 ft 7 in) and an above-water diameter of 6 m (20 ft). 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. They 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. 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 1 m (3 ft 3 in) wide, 0.5 m (1 ft 8 in) deep, and over 0.5 km (0.31 mi) long. It has been hypothesized that beavers' canals are not only transportation routes but an extension of their " central place " around

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732-460: 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. Compared to many other rodents, a beaver's brain has

793-422: 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. In the early Miocene (about 24 mya), castorids evolved

854-463: A number of freshwater habitats , such as rivers, streams, lakes and ponds. They are herbivorous , consuming tree bark , aquatic plants , grasses and sedges . Beavers build dams and lodges using tree branches, vegetation, rocks and mud; they chew down trees for building material. Dams restrict water flow, and lodges serve as shelters. Their infrastructure creates wetlands used by many other species, and because of their effect on other organisms in

915-459: A pond for them to live in, and for lodges, which act as shelters and refuges from predators and the elements. Without such material, beavers dig burrows into a bank to live. Dam construction begins in late summer or early fall, and they repair them whenever needed. Beavers can cut down trees up to 15 cm (5.9 in) wide in less than 50 minutes. Thicker trees, at 25 cm (9.8 in) wide or more, may not fall for hours. When chewing down

976-861: A role. 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. After their first year, young beavers help their families with construction. Beavers sexually mature around 1.5–3 years. 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. Semiaquatic In biology , being semi-aquatic refers to various macro organisms that live regularly in both aquatic and terrestrial environments . When referring to animals ,

1037-531: A taxon to be definitively extinct is difficult. Taxa that have previously been declared extinct may reappear over time. Species that were once considered extinct and then reappear unscathed are characterized by the term "the Lazarus effect", or are also called a Lazarus species . For example, a study determined that 36% of supposed mammalian extinction had been proven, while the other 64% had insufficient evidence to be declared extinct or had been rediscovered. Currently,

1098-409: A thick enamel that is colored orange or reddish-brown by iron compounds. 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. The eyes, ears and nostrils are arranged so that they can remain above water while the rest of

1159-421: 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. Beavers start building dams when they hear running water, and the sound of a leak in a dam triggers them to repair it. To build

1220-399: Is broadly agreed or certified that no members of the group are still alive. Conversely, an extinct taxon can be reclassified as extant if there are new discoveries of living species (" Lazarus species "), or if previously known extant species are reclassified as members of the taxon. Most biologists, zoologists , and botanists are in practice neontologists, and the term neontologist

1281-494: 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. The IUCN Red List of mammals lists both beaver species as least concern . The North American beaver is widespread throughout most of the United States and Canada and can be found in northern Mexico. The species

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1342-659: Is the family, which is composed of an adult male and an adult female in a monogamous pair and their offspring. Beaver families can have as many as ten members; groups about this size require multiple lodges. Mutual grooming and play fighting maintain bonds between family members, and aggression between them is uncommon. 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

1403-486: Is the source for several European placenames , including those of Beverley , Bièvres , Biberbach , Biebrich , Bibra , Bibern , Bibrka , Bobr , Bober , Bóbrka , Bjurholm , Bjurälven , and Bjurum . The genus name Castor has its origin in the Greek word κάστωρ kastōr and translates as ' beaver ' . Carl Linnaeus coined the genus name Castor in 1758 as well as the specific (species) epithet fiber for

1464-443: Is used largely by paleontologists referring to non- paleontologists . Stephen Jay Gould said of neontology: All professions maintain their parochialisms , and I trust that nonpaleontological readers will forgive our major manifestation . We are paleontologists, so we need a name to contrast ourselves with all you folks who study modern organisms in human or ecological time . You therefore become neontologists. We do recognize

1525-644: 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. The English word beaver comes from the Old English word beofor or befor and is connected to the German word biber and the Dutch word bever . The ultimate origin of the word is an Indo-European root for ' brown ' . Cognates of beaver

1586-556: The International Union for Conservation of Nature considers a taxon to be recently extinct if the extinction occurred after 1500 C.E. A recently considered extinct mammal was the Bouvier's red colobus monkey, who was considered extinct up until 2015 when it was rediscovered after 40 years with no recorded sightings. Neontology's fundamental theories rely on biological models of natural selection and speciation that connect genes,

1647-693: 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 cavities (as opposed to the square ones of the North American species), a lighter fur color, and a narrower tail. Agnotocastor coloradensis Agnotocastor praetereadens Anchitheriomys sp. [REDACTED] Castorinae (modern beavers) [REDACTED] Castoroidinae [REDACTED] Agnotocastor sp. Migmacastor procumbodens Palaeocastorinae [REDACTED] Heteromyidae (kangaroo rats and allies) [REDACTED] Geomyidae (gophers) [REDACTED] Beavers belong to

1708-621: The Scandinavian Peninsula . Beginning in 2009, beavers have been successfully reintroduced to parts of Great Britain. In 2020, the total Eurasian beaver population in Europe was estimated at over one million. Small native populations are also present in Mongolia and northwestern China; their numbers were estimated at 150 and 700, respectively, as of 2016. Under New Zealand's Hazardous Substances and New Organisms Act 1996 , beavers are classed as

1769-401: The ecosystem , beavers are considered a keystone species . Adult males and females live in 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 territories and mark them using scent mounds made of mud, debris, and castoreum —a liquid substance excreted through

1830-1026: 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 climates . 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. In a study of Wyoming streams and rivers, watercourses with beavers had 75 times as many ducks as those without. 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. Beaver-caused ice thawing in northern latitudes allows Canada geese to nest earlier. Other semi-aquatic mammals, such as water voles , muskrats , minks , and otters , will shelter in beaver lodges. Beaver modifications to streams in Poland create habitats favorable to bat species that forage at

1891-586: The Eurasian species. German zoologist Heinrich Kuhl coined C. canadensis in 1820, many scientists considered both names synonymous for one same species until the 1970s, when 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. Twenty-five subspecies have been classified for C. canadensis , and nine have been classified for C. fiber . There are two extant species:

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1952-486: The animal warm, to help it float in water, and to protect it against predators. Guard hairs are 5–6 cm (2.0–2.4 in) long and typically reddish brown, but can range from yellowish brown to nearly black. The underfur is 2–3 cm (0.79–1.18 in) long and dark gray. Beavers molt every summer. Beavers have large skulls with powerful chewing muscles . They have four chisel-shaped incisors that continue to grow throughout their lives. The incisors are covered in

2013-555: 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. Beaver ponds have been shown to be beneficial to frog populations by protecting areas for larvae to mature in warm water. The stable waters of beaver ponds also provide ideal habitat for freshwater turtles . Beavers help waterfowl by creating increased areas of water. The widening of

2074-412: 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 . They have also been recorded to be infected with the rabies virus . Beavers need trees and shrubs to use as building material for dams , which restrict flowing water to create

2135-568: 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. Beavers can hold their breath for as long as 15 minutes but typically remain underwater for no more than five or six minutes. Dives typically last less than 30 seconds and are usually no more than 1 m (3 ft 3 in) deep. When diving, their heart rate decreases to 60 beats per minute, half its normal pace, and blood flow

2196-571: 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 by

2257-637: 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. 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 webbing between

2318-441: 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. Microorganisms in

2379-403: The caecum allow them to process around 30 percent of the cellulose they eat. 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 glands . The castor sacs secrete castoreum ,

2440-526: 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. Castor may have competed with members of Castoroidinae, which led to niche differentiation . The fossil species C. praefiber was likely an ancestor of the Eurasian beaver. C. californicus from the Early Pleistocene of North America

2501-427: The constantly changing water levels, leading to greater carbon storage . Beaver ponds, and the wetlands that succeed them, remove sediments and pollutants from waterways, and can stop the loss of important soils. These ponds can increase the productivity of freshwater ecosystems by accumulating nitrogen in sediments. Beaver activity can affect the temperature of the water; in northern latitudes, ice thaws earlier in

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2562-449: The continent to rebound to an estimated 6–12   million by the late 20th century; still far lower than the originally estimated 60–400   million North American beavers before the fur trade. The introduced population in Tierra del Fuego is estimated at 35,000–50,000 individuals as of 2016. The Eurasian beaver's range historically included much of Eurasia, but was decimated by hunting by

2623-807: 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 river and Dnieper Basin in Belarus, and the Voronezh river in Russia. The beaver has since recolonized parts of its former range, aided by conservation policies and reintroductions . Beaver populations now range across western, central, and eastern Europe, and western Russia and

2684-810: The indigenous forest. Unlike trees in North America, many trees in South America cannot grow back after being cut down. Beaver activity impacts communities of aquatic invertebrates . Damming typically leads to an increase of slow or motionless water species, like dragonflies , oligochaetes , snails , and mussels . This is to the detriment of rapid water species like black flies , stoneflies , and net-spinning caddisflies . 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. The presence of beavers can increase wild salmon and trout populations, and

2745-431: The lodge and/or food cache. As they drag wood across the land, beavers leave behind trails or "slides", which they reuse when moving new material. 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. When building dams, beavers alter

2806-464: The paths of streams and rivers, allowing for the creation of extensive wetland habitats. 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. Beaver dams also lead to higher water tables in mineral soil environments and in wetlands such as peatlands . In peatlands particularly, their dams stabilize

2867-499: The population structure than paleontology does. When the scientific community accepted the synthetic theory of evolution , taxonomies became phylogenetic . As a result, information gaps arose within the fossil record of species, especially in Homo sapiens . The anthropologists who accepted the synthetic theory reject the idea of an "ape-man" because the concept had mistaken paleontology with neontology. An ape-man, in actuality, would be

2928-404: The presence of a third set of premolars (P3), a 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 snout . More 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,

2989-758: 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   million years ago ( myr ). The more basal castorids had several unique features: more complex occlusion between cheek teeth, parallel rows of upper teeth, premolars that were only slightly smaller than molars,

3050-673: The shore and covered in sticks. 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. The above-water space inside the lodge is known as the "living chamber", and a "dining area" may exist close to the water entrance. Families routinely clean out old plant material and bring in new material. 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

3111-705: The term describes those that actively spend part of their daily time in water (in which case they can also be called amphibious ), or land animals that have spent at least one life stages (e.g. as eggs or larvae ) in aquatic environments. When referring to plants , the term describes land plants whose roots have adapted well to tolerate regular, prolonged submersion in water, as well as emergent and (occasionally) floating-leaved aquatic plants that are only partially immersed in water. Examples of semi-aquatic animals and plants are given below. Semi aquatic animals include: Semi aquatic plants include: Extant taxa A taxon can be classified as extinct if it

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3172-489: The toes , and the second innermost toe has a "double nail" used for grooming. Beavers can swim at 8 km/h (5.0 mph); only their webbed hind feet are used to swim, while the front feet fold under the chest. On the surface, the hind limbs thrust one after the other; while underwater, they move at the same time. Beavers are awkward on land but can move quickly when they feel threatened. They can carry objects while walking on their hind legs. The beaver's distinctive tail has

3233-725: The unbalanced and parochial nature of this dichotomous division. Neontological evolutionary biology has a temporal perspective between 100 and 1000 years. Neontology's fundamental basis relies on models of natural selection as well as speciation . Neontology's methods, when compared to evolutionary paleontology , have a greater emphasis on experiments. There are more frequent discontinuities present in paleontology than in neontology, because paleontology involves extinct taxa. Neontology has organisms actually present and available to sample and perform research on. Neontology's research method uses cladistics to examine morphologies and genetics . Neontology data has more emphasis on genetic data and

3294-508: The warmer beaver-dammed waters. Beavers may contribute to climate change . In Arctic areas, the floods they create can cause permafrost to thaw, releasing methane into the atmosphere . As wetlands are formed and riparian habitats are enlarged, aquatic plants colonize the newly available watery habitat. One study in the Adirondacks found that beaver engineering lead to an increase of more than 33 percent in herbaceous plant diversity along

3355-414: The water and to a lesser extent in the lodge, for half a minute to three minutes. Up to four young, or kits, are born in spring and summer, after a three or four-month gestation . Newborn beavers are precocial with a full fur coat, and can open their eyes within days of birth. Their mother is the primary caretaker, while their father maintains the territory. Older siblings from a previous litter also play

3416-543: The water surface and "prefer moderate vegetation clutter". Large herbivores, such as some deer species, benefit from beaver activity as they can access vegetation from fallen trees and ponds. Beavers are mainly nocturnal and crepuscular , and spend the daytime in their shelters. In northern latitudes, beaver activity is decoupled from the 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. The core of beaver social organization

3477-520: The water's edge. 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. Riparian ecosystems in arid areas appear to sustain more plant life when beaver dams are present. Beaver ponds act as a refuge for riverbank plants during wildfires , and provide them with enough moisture to resist such fires. Introduced beavers at Tierra del Fuego have been responsible for destroying

3538-545: The water, but will roam several hundred meters to find more. Beavers have also been recorded in mountainous areas. 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. Beavers have an herbivorous and

3599-526: The winter, piling wood in the deepest part of their pond where it cannot be reached by other browsers . This cache is known as a "raft"; when the top becomes frozen, it creates a "cap". 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. Beavers usually live up to 10 years. Felids , canids , and bears may prey upon them. Beavers are protected from predators when in their lodges, and prefer to stay near water. Parasites of

3660-473: Was introduced to Finland in 1937 (and then spread to northwestern Russia) and to Tierra del Fuego, Patagonia , in 1946. As of 2019, the introduced population of North American beavers in Finland has been moving closer to the habitat of the Eurasian beaver. Historically, the North American beaver was trapped and nearly extirpated because its fur was highly sought after. Protections have allowed the beaver population on

3721-644: Was similar to but larger than the extant North American beaver.' Beavers are the second-largest living rodents, after capybaras . They have a head–body length of 80–120 cm (31–47 in), with a 25–50 cm (9.8–19.7 in) tail, a shoulder height of 30–60 cm (12–24 in), and generally weigh 11–30 kg (24–66 lb), but can be as heavy as 50 kg (110 lb). Males and females are almost identical externally. Their bodies are streamlined like marine mammals and their robust build allows them to pull heavy loads. A beaver coat has 12,000–23,000 hairs/cm (77,000–148,000 hairs/in) and functions to keep

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