North American beaver

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North American beaver
American Beaver.jpg
A male North American beaver
Status TNC G5.svg
Secure  (NatureServe) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Castoridae
Genus: Castor
Species:
C. canadensis
Binomial name
Castor canadensis
Kuhl, 1820 [3]
Subspecies [4] [5] [6] [7] [8]
List
    • C. c. acadicus Bailey and Doutt, 1942 [9]
    • C. c. baileyi Nelson, 1927 [10]
    • C. c. belugae Taylor, 1916 [11] :  429–433 
      Cook Inlet beaver
    • C. c. caecator Bangs (1913:513) [12]
      Newfoundland beaver
    • C. c. canadensis Kuhl 1820 [3]
      Canadian beaver
    • C. c. carolinensis Rhoads 1898 [13] : 420–421 
      Carolina beaver
    • C. c. concisor Warren and Hall, 1939 [14]
    • C. c. duchesnei Durrant and Crane, 1948 [15]
    • C. c. frondator Mearns, 1897 [16]
      Sonora beaver
    • C. c. idoneus Jewett and Hall, 1940 [17]
    • C. c. labradorensis Bailey and Doutt, 1942 [9]
    • C. c. leucodonta Gray, 1869 [18]
      Pacific beaver
    • C. c. mexicanus Bailey, 1913 [19]
      Rio Grande beaver
    • C. c. michiganensis Bailey 1913 [19]
      Woods beaver
    • C. c. missouriensis Bailey 1919 [20]
      Missouri River beaver
    • C. c. pacificus Rhoads 1892 [13] : 422–423 
      Washington beaver
    • C. c. pallidus Durrant and Crane, 1948 [15]
    • C. c. phaeus Heller, 1909 [21]
      Admiralty beaver
    • C. c. repentinus Goldman, 1932 [22]
    • C. c. rostralis Durrant and Crane, 1948 [15]
    • C. c. sagittatus Benson, 1933 [23]
    • C. c. shastensis (Taylor, 1916) [11] :  433–436 
      Shasta beaver
    • C. c. subauratus (Taylor, 1912) [24] [25]
      California golden beaver
    • C. c. taylori Davis, 1939 [26]
    • C. c. texensis Bailey, 1905 [27]
      Texas beaver
American beaver map.png
Distribution of the North American beaver (dark green – native, light green – introduced)
Synonyms

Castor fiber canadensis

The North American beaver (Castor canadensis) is one of two extant beaver species, along with the Eurasian beaver (Castor fiber). [4] It is native to North America and has been introduced in South America (Patagonia) and Europe (primarily Finland and Karelia). The North American beaver is one of the official national wildlife of Canada symbols and is the official state mammal of Oregon and New York. [28] North American beavers are widespread across the continental United States, Canada, southern Alaska, and some parts of northern Mexico.

Contents

In Canada and the United States, the North American beaver is often referred to simply as "beaver", although this can cause some confusion because another distantly related rodent, Aplodontia rufa , is often called the "mountain beaver". Other vernacular names, including American beaver [4] and Canadian beaver, [29] distinguish this species from the other extant beaver species, Castor fiber , which is native to Eurasia.

Taxonomy

Evolution

The first fossil records of beaver are 10 to 12 million years old in Germany, and they are thought to have migrated to North America across the Bering Strait. The oldest fossil record of beavers in North America are of two beaver teeth near Dayville, Oregon, and are 7 million years old. [30]

Subspecies

At one time, 25 subspecies of beavers were identified in North America, with distinctions based primarily on slight morphological differences and geographical isolation at the time of discovery. However, modern techniques generally use genetics rather than morphology to distinguish between subspecies, and currently the Integrated Taxonomic Information System (which provides authoritative [31] taxonomic information on plants, animals, fungi, and microbes of North America and the world) does not recognize any subspecies of C. canadensis, though a definitive genetic analysis has not been performed. Such an analysis would be complicated by the fact that substantial genetic mixing of populations has occurred because of the numerous reintroduction efforts intended to help the species recover following extirpation from many regions.

The most widespread (formerly recognized) subspecies, which perhaps are now best thought of as populations with some distinct physical characteristics, are C. c. acadicus (New England beaver), C. c. canadensis (Canadian beaver), C. c. carolinensis (Carolina beaver), and C. c. missouriensis (Missouri River beaver). [32] The Canadian beaver originally inhabited almost all of the forested area of Canada, [33] and because of its more valued fur, was often selected for reintroductions elsewhere. The Carolina beaver is found in the southeastern United States; the Missouri River beaver, as its name suggests, is found in the Missouri River and its tributaries; and C. c. acadicus is found throughout the New England area in the northeastern United States.

Description

North American beaver skeleton (Museum of Osteology) Beaver skeleton.jpg
North American beaver skeleton (Museum of Osteology)
Lithograph of a Canadian beaver, 1819. Canadian Beaver - Castor du Canada.jpg
Lithograph of a Canadian beaver, 1819.

The beaver is the largest rodent in North America and competes with its Eurasian counterpart, the European beaver, for being the third-largest in the world, both following the South American capybara and lesser capybara. The European species is slightly larger on average but the American has a larger known maximum size. Adults usually weigh from 11 to 32 kg (24 to 71 lb), with 20 kg (44 lb) being typical. In New York, the average weight of adult male beavers was 18.9 kg (42 lb), while non-native females in Finland averaged 18.1 kg (40 lb). However, adults of both sexes averaged 16.8 kg (37 lb) in Ohio. [34] [35] [36] The species seems to conform to Bergmann's rule, as northern animals appear to be larger. In the Northwest Territory, adults weighed a median of 20.5 kg (45 lb). [37] The American beaver is slightly smaller in average body mass than the Eurasian species. [35] The head-and-body length of adult North American beavers is 74–90 cm (29–35 in), with the tail adding a further 20–35 cm (7.9–13.8 in). Very old individuals can exceptionally exceed normal sizes, weighing more than 40 kg (88 lb) or even as much as 50 kg (110 lb) (higher than the maximum known for the Eurasian beaver). [38] [39] [40] [41]

Like the capybara, the beaver is semiaquatic. The beaver has many traits suited to this lifestyle. It has a large, flat, paddle-shaped tail and large, webbed hind feet. The unwebbed front paws are smaller, with claws. The forepaws are highly dextrous, and are used both for digging, and to fold individual leaves into their mouth and to rotate small, pencil-sized stems as they gnaw off bark. [42] The eyes are covered by a nictitating membrane which allows the beaver to see under water. The nostrils and ears are sealed while submerged. Their lips can be closed behind their front teeth so that they can continue to gnaw underwater. [43] A thick layer of fat under its skin insulates the beaver from its coldwater environment.

The beaver's fur consists of long, coarse outer hairs and short, fine inner hairs (see Double coat). The fur has a range of colors, but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur. There is also another set of oil glands producing unique chemical identifiers in the form of waxy esters and fatty acids. [42] The lush, workable fur was made into a number of products, most notably hats. Demand for furs for hats drove beavers nearly to the point of extinction, and the North American species was saved principally by a sudden change in style.

The beaver possesses continuously (or constantly) growing incisors, and is a hindgut fermenter whose cecum, populated by symbiotic bacteria, helps to digest plant-based material. These traits are not unique to beavers, and are in fact present among all rodents. [44] Nonetheless, the beaver is remarkably specialized for the efficient digestion of its lignocellulose-heavy diet. [45]

Brain anatomy of the beaver is not particularly specialized for its semiaquatic life history. The brain masses of a beaver weighing 11.7 and 17 kg are 41 and 45 g respectively. C. canadensis has an encephalization quotient of 0.9 compared to other rodents; this is intermediate between similar terrestrial rodents and arboreal squirrels, and higher than similar aquatic terrestrial rodents, the muskrats and nutria. The cerebrum is well developed, and the neocortex comparatively large. Larger areas of the beaver's somatosensory cortex are dedicated to the processing of stimuli from the lips and the hands, more so than the tail and whiskers, which play a relatively minor role. The visual area of the brain is smaller than the gray squirrel. [43]

Distribution

Before their near-extirpation by trapping in North America, beavers were practically ubiquitous and lived from south of the arctic tundra to the deserts of northern Mexico, and from the Atlantic to the Pacific Oceans. [46] [47] [48] They are widely distributed in boreal and temperate ecoregions, where populations are rebounding from historic over-exploitation. Recently, beaver have been observed colonizing arctic tundra, likely as a result of climate-induced increases in riparian shrubs. [49] [50] [51]

Physician naturalist Edgar Alexander Mearns' 1907 report of beaver on the Sonora River may be the earliest report on the southernmost range of this North American aquatic mammal. [52] However, beavers have also been reported both historically and contemporarily in Mexico on the Colorado River, Bavispe River, and San Bernardino River in the Mexican states of Sonora and Chihuahua. [53] [54] [55]

Behavior

Beaver lodge, Ontario, Canada Biberburg.jpg
Beaver lodge, Ontario, Canada
Beaver dam, northern California, USA BeaverDam 8409.jpg
Beaver dam, northern California, USA
Beavers use rocks for their dams when mud and branches are less available as seen on Bear Creek, a tributary to the Truckee River, in Alpine Meadows, California. Rock Beaver Dam on Bear Creek, Jan. 2011 Guzzi.jpg
Beavers use rocks for their dams when mud and branches are less available as seen on Bear Creek, a tributary to the Truckee River, in Alpine Meadows, California.

Beavers are active mainly at night. They are excellent swimmers and may remain submerged up to 15 minutes. More vulnerable on land, they tend to remain in the water as much as possible. [56] They use their flat, scaly tail both to signal danger by slapping the surface of the water and as a location for fat storage.

They construct their homes, or "lodges", out of sticks, twigs, rocks, and mud in lakes, streams, and tidal river deltas. [57] These lodges may be surrounded by water, or touching land, including burrows dug into river banks. Beavers are well known for building dams across streams and constructing their lodges in the artificial ponds which form. When building in a pond, the beavers first make a pile of sticks and then eat out one or more underwater entrances and two platforms above the water surface inside the pile. The first is used for drying off. Towards winter, the lodge is often plastered with mud which, when it freezes, has the consistency of concrete. A small air hole is left in the top of the lodge.

Dam-building

The purpose of the dam is to create a deepwater refuge enabling the beaver to escape from predators. When deep water is already present in lakes, rivers, or larger streams, the beaver may dwell in a bank burrow and bank lodge with an underwater entrance. The beaver dam is constructed using branches from trees the beavers cut down, as well as rocks, grass, and mud. Where naturally-occurring woody material is limiting, beavers may build their dams largely of rocks. [58] The inner bark, twigs, shoots, and leaves of such trees are also an important part of the beaver's diet. [59] The trees are cut down using their strong incisor teeth. Their front paws are used for digging and carrying and placing materials. The sound of running water dictates when and where a beaver builds its dam. Besides providing a safe home for the beaver, beaver ponds also provide habitat for waterfowl, fish, and other aquatic animals. Their dams help reduce soil erosion and can help reduce flooding. However, beaver dams are not permanent and depend on the beavers' continued presence for their maintenance. Beavers generally concentrate on building and repairing dams in the fall in preparation for the coming winter. In northern areas, they often do not repair breaches in the dam made by otters, and sometimes breach the dam themselves and lower the water level in the pond to create more breathing space under the ice or get easier access to trees below the dam. In a 1988 study in Alberta, Canada, no beavers repaired "sites of water loss" during the winter. Of 178 sites of water loss, beavers repaired 78 when water was opened, and did not repair 68. The rest were partially repaired. [60]

Beavers are best known for their dam-building. They maintain their pond-habitat by reacting quickly to the sound of running water, and damming it up with tree branches and mud. Early ecologists believed that this dam-building was an amazing feat of architectural planning, indicative of the beaver's high intellect. This theory was tested when a recording of running water was played in a field near a beaver pond. Although it was on dry land, the beaver covered the tape player with branches and mud. [61] The largest beaver dam is 2,790 ft (850 m) in length—more than half a mile long—and was discovered via satellite imagery in 2007. [62] It is located on the southern edge of Wood Buffalo National Park in northern Alberta and is more than twice the width of the Hoover Dam which spans 1,244 ft (379 m). [63] [64]

C. c. canadensis, feeding in winter Beaver in Winter, Gatineau Park.jpg
C. c. canadensis, feeding in winter

Normally, the purpose of the dam is to provide water around their lodges that is deep enough that it does not freeze solid in winter. The dams also flood areas of surrounding forest, giving the beaver safe access to an important food supply, which is the leaves, buds, and inner bark of growing trees. In colder climates where their pond freezes over, beavers also build a food cache from this food resource. [42] To form the cache, beavers collect food in late fall in the form of tree branches, storing them under water (usually by sticking the sharp chewed base of the branches into the mud on the pond bottom), where they can be accessed through the winter. Often, the pile of food branches projects above the pond and collects snow. This insulates the water below it and keeps the pond open at that location. [65] The frozen combination of branches and ice is known as a cap, sealing the food cache. Beavers often maintain an underwater entrance to their dam, and they can access their food cache from their lodge by swimming under the ice. In warmer climes, a winter food store is less common. [42]

Muskrats have been thought to steal food from beaver lodges, but seemingly cooperative relationships exist, with beavers allowing muskrats to reside in their lodge if they gather fresh reeds. [66]

Canals

Another component to the beaver's habitat is the canal. Canals are used to float logs to a pond, and dams may also be used to maintain the water levels in these canals. Several land trails can extend from the canals. [67] Despite being widespread in some beaver-inhabited areas, beaver canals and their environmental effects are much less studied than beaver dams. Beaver primarily develop canals to increase accessibility of river resources, facilitate transport of acquired resources, and to decrease the risk of predation. Beaver canals can be over 0.5 km in length. [68] Beavers build canals by pushing through soil and vegetation using their forelimbs.

It has been hypothesized that beavers' canals are not only transportation routes to extend foraging, but also an extension of their "central place" around the lodge and/or food cache. A 2012 study of beavers' mark on the landscape found that cut stumps were negatively related to distance from beaver canals, but not to the central body of water. This finding suggested that beavers may consider the canals to be part of their "central place" as far as foraging activity is concerned. [69]

Social behavior

A group of Canadian beavers and their dam on a river. The Beaver Beavers and their habitations.jpg
A group of Canadian beavers and their dam on a river.

Communication is highly developed in beaver, including scent marking, vocalization, and tail slapping. Beaver deposit castoreum on piles of debris and mud called scent mounds, which are usually placed on or near lodges, dams, and trails less than a meter from water. Over 100 of such mounds can be constructed within one territory. [42] Beaver colonies with close neighbors constructed more "scent mounds" than did isolated colonies, and the number of scent mounds at each active lodge is correlated with the distance to the nearest occupied lodge. [70]

Although seven vocal sounds have been described for beaver, most zoologists recognize only three: a whine, hiss, and growl. Vocalizations and tail slapping may be used to beg for food, signal to family members to warn of predators, or to drive away or elicit a response from predators.

Beavers usually mate for life, forming familial colonies. Beaver "kits" are born precocious and with a developed coat. The young beaver "kits" typically remain with their parents up to two years. Kits express some adult behaviors, but require a long period in the family to develop their dam construction skills, and other abilities required for independent life. [42]

Diet

Beavers are herbivorous generalists with sophisticated foraging preferences. Beavers consume a mix of herbaceous and woody plants, which varies considerably in both composition and species diversity by region and season. [42] They prefer aspen and other poplars, but also take birch, maple, willow, alder, black cherry, red oak, beech, ash, hornbeam, and occasionally pine and spruce. [65] They also eat cattails, water lilies, and other aquatic vegetation, especially in the early spring. Contrary to widespread belief, they do not eat fish. [71]

Beavers select food based on taste, coarse physical shape, and odor. Beavers feed on wood, bark, cambium, [72] branches, twigs, roots, buds, [72] leaves, stems, sprouts, and in some cases, the sap and storax of pine and sweetgum. [42]

When herbaceous plants are actively growing, they make up much of the beaver's diet. In the winter, beavers switch to woody plants and the food they have stored over the winter. The protein to calorie ratio of a beaver's diet is 40 mg/calorie in summer and 8 mg/calorie for the rest of the year. In northern latitudes, the water lilies Nymphaea and Nuphar are the most important herbaceous component. The rhizomes are stored in the food cache and remain actively growing. [42]

Willow is an important protein source and is likely to be available for the longest period of time in a beaver's habitat especially in the far north. When available, aspen and poplar are preferred over willow. Conifers are also cut or gnawed by beavers, and used for food and/or building material.

Beavers do not necessarily use the same trees as construction material and as food. Inedible material is more likely to be used as the cap of a beaver family's food cache, the upper part which is frozen in the ice, while the cache itself is composed of edible, high quality branches, which remain unfrozen and accessible. [42]

Beavers avoid red maple, which can be the only tree left standing at the edges of some beaver ponds. [42] [73]

The beaver's gut microbiome is complex and specialized for a wood-heavy diet, sharing a number of similarities with other mammalian herbivores. However the microbial community in the beaver shows less taxonomic diversity than the "typical" mammalian gut. The major operational taxonomic units (OTU) are Bacteroidota and Bacillota. [45]

Predators

Brooklyn Museum - American Beaver - John J. Audubon Brooklyn Museum - American Beaver - John J. Audubon.jpg
Brooklyn Museum – American Beaver – John J. Audubon

Common natural predators include coyotes, wolves, and mountain lions. [74] American black bears may also prey on beavers if the opportunity arises, often by smashing their paws into the beavers' lodges. [75] [76] [77] Perhaps due to differing habitat preferences, grizzly bears were not known to hunt beavers in Denali National Park, Alaska. [78] Less significant predators include wolverines, which may attack a rare beaver of up to adult size, and Canada lynx, bobcats, and foxes (predators of kits or very sick or injured animals, rather than full-grown beavers due to their increasingly smaller size). American alligators, which only minimally co-exist in the wild with beavers, also seldom threaten them. Both golden eagles (Aquila chrysaetos) and bald eagles (Haliaeetus leucocephalus) may on occasion prey on a beaver, most likely only small kits. [79] Despite repeated claims, no evidence shows that North American river otters are typically predators of beavers but anecdotally may take a rare beaver kit. [80]

Reproduction

North American beavers have one litter per year, coming into estrus for only 12 to 24 hours, between late December and May but peaking in January. Unlike most other rodents, beaver pairs are monogamous, staying together for multiple breeding seasons. Gestation averages 128 days and they have a range of three to six kits per litter (usually 4-5). [81] Most beavers do not reproduce until they are three years of age, but about 20% of two-year-old females reproduce. [82]

Differences from European beaver

Skulls of a European (left) and North American (right) beaver. Castor fiber vs. Castor canadensis skulls.jpg
Skulls of a European (left) and North American (right) beaver.

Although North American beavers are superficially similar to the European beaver (Castor fiber), several important differences exist between the two species. North American beavers tend to be slightly smaller, with smaller, more rounded heads; shorter, wider muzzles; thicker, longer, and darker underfur; wider, more oval-shaped tails; and longer shin bones, allowing them a greater range of bipedal locomotion than the European species. North American beavers have shorter nasal bones than their European relatives, with the widest point being at the middle of the snout for the former, and in the tip for the latter. The nasal opening for the North American species is square, unlike that of the European species, which is triangular. The foramen magnum is triangular in the North American beaver, and rounded in the European. The anal glands of the North American beaver are smaller and thick-walled with a small internal volume compared to that of the European species. Finally, the guard hairs of the North American beaver have a shorter hollow medulla at their tips. Fur color is also different. Overall, 50% of North American beavers have pale brown fur, 25% are reddish brown, 20% are brown, and 6% are blackish, while in European beavers, 66% have pale brown or beige fur, 20% are reddish brown, nearly 8% are brown, and only 4% have blackish coats. [83]

The two species are not genetically compatible. North American beavers have 40 chromosomes, while European beavers have 48. Also, more than 27 attempts were made in Russia to hybridize the two species, with one breeding between a male North American beaver and a female European resulting in one stillborn kit. These factors make interspecific breeding unlikely in areas where the two species' ranges overlap. [83]

Ecology

Taxidermied North American beaver at the Milwaukee Public Museum Milwaukee Public Museum March 2023 78 (Wisconsin Mammals--Beaver Pond, Northern Wisconsin Woodlands).jpg
Taxidermied North American beaver at the Milwaukee Public Museum

The beaver was trapped out and almost extirpated in North America because its fur and castoreum were highly sought after. [47] The beaver furs were used to make clothing and beaver hats. In the United States, extensive trapping began in the early 17th century, with more than 10,000 beaver per year taken for the fur trade in Connecticut and Massachusetts between 1620 and 1630. [84] From 1630 to 1640, around 80,000 beavers were taken annually from the Hudson River and western New York. [85] From 1670 onwards, the Hudson's Bay Company sent two or three trading ships into the bay every year to take furs to England from Canada. Archaeological and historical evidence suggests that beaver ponds created "moth-hole like" habitats in the deciduous forest that dominated eastern North America. This nonforest habitat attracted both Native American and early colonial hunters to the abundant fish, waterfowl, and large game attracted to the riparian clearings created by these aquatic mammals. The first colonial farmers were also attracted to the fertile, flat bottomlands created by the accumulated silt and organic matter in beaver ponds. [86]

As eastern beaver populations were depleted, English, French, and American trappers pushed west. Much of the westward expansion and exploration of North America was driven by the quest for this animal's fur. Before the 1849 California Gold Rush, an earlier, 19th-century California Fur Rush drove the earliest American settlement in that state. During the roughly 30 years (1806–1838) of the era of the mountain man, the West from Missouri to California and from Canada to Mexico was thoroughly explored and the beaver was brought to the brink of extinction.

With protection in the late 19th and early 20th centuries, the current beaver population has rebounded to an estimated 10 to 15 million; this is a fraction of the originally estimated 100 to 200 million North American beavers before the days of the fur trade. [87] [88]

A wire mesh fence installed around a tree trunk in Toronto. Wire mesh fences are used in an attempt to prevent beavers' damage. Beavers Ain't Chopping That Tree Down (4340897705).jpg
A wire mesh fence installed around a tree trunk in Toronto. Wire mesh fences are used in an attempt to prevent beavers' damage.

These animals are considered pests in parts of their range because their dams can cause flooding, or because their habit of felling trees can pose danger to people, as in Charlotte, North Carolina's Park Road Park. [90] Because they are persistent in repairing damage to the dam, they were historically relocated or exterminated. Nonlethal methods of containing beaver-related flooding have been developed. [91] One such flow device has been used by both the Canadian and U.S. governments, called "beaver deceivers" or levelers, invented and pioneered by wildlife biologist Skip Lisle. [92]

The beaver is a keystone species, increasing biodiversity in its territory through creation of ponds and wetlands. [93] As wetlands are formed and riparian habitats enlarged, aquatic plants colonize newly available watery habitat. Insect, invertebrate, fish, mammal, and bird diversities are also expanded. [94] Effects of beaver recolonization on native and non-native species in streams where they have been historically absent, particularly dryland streams, is not well-researched. [95]

Relationship with humans

As introduced non-native species

Beaver damage on the north shore of Robalo Lake, Navarino Island, Chile Beaver damage navarino chile.JPG
Beaver damage on the north shore of Robalo Lake, Navarino Island, Chile

In the 1940s, beavers were brought to Tierra del Fuego in southern Chile and Argentina for commercial fur production and introduced near Fagnano Lake. Although the fur enterprise failed, 25 mating pairs of beavers were released into the wild. Having no natural predators in their new environment, they quickly spread throughout the main island, and to other islands in the archipelago, reaching a number of 100,000 individuals within just 50 years. Although they have been considered an invasive species, it has been more recently shown that the beaver have some beneficial ecological effects on native fish and should not be considered wholly detrimental. [96] Although the dominant Lenga beech (Nothofagus pumilio) forest can regenerate from stumps, most of the newly created beaver wetlands are being colonized by the rarer native Antarctic beech (Nothofagus antarctica). It is not known whether the shrubbier Antarctic beech will be succeeded by the originally dominant and larger Lengo beech, however, and the beaver wetlands are readily colonized by non-native plant species. [96] In contrast, areas with introduced beaver were associated with increased populations of the native catadromous puye fish (Galaxias maculatus). [97] [98] Furthermore, the beavers did not seem to have a highly beneficial impact on the exotic brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss) which have negative impacts on native stream fishes in the Cape Horn Biosphere Reserve, Chile. [98] They have also been found to cross saltwater to islands northward; and reached the Chilean mainland in the 1990s. [99] On balance, because of their landscape-wide modifications to the Fuegian environment and because biologists want to preserve the unique biota of the region, most favor their removal. [100]

North American beavers were released in Finland in 1937, before it was realized that they formed a separate species; following this, 7 beavers expanded to a population of 12,000 within 64 years. [101] Eurasian beavers had earlier been extirpated from the region, so the release was intended as a reintroduction project. [102] By 1999, it was estimated that 90% of beavers in Finland were the American species. However, the species is not always considered invasive, as in Europe it has a similar keystone effect to European beavers, which have not recolonized the area. The beaver population has been controlled by issuing hunting licenses. [103] A report in 2010 concluded that while the current population of American beavers was not problematic, as the species has larger litters than European beavers and builds somewhat larger dams, it could become a problem if its range continues expanding into Russia, but this does not seem to be taking place. [104]

In Europe, significant invasive populations of Canadian beaver are only present in Finland and Karelia, as the boundary between species has somewhat stabilized, but smaller occurrences have been detected elsewhere. [102] Ephemeral populations of C. canadensis in Germany and Poland were found from the 1950s to 1970s. Zoo escapes in 2006 created a small population of invasive C. canadensis in Luxembourg, Rhineland-Palatinate and Belgium. [101] American beavers have not been detected in Sweden, Norway, or Denmark. [104]

As food

Beaver meat is similar tasting to lean beef, but care must be taken to prevent contamination from the animal's strong castor (musk) gland. It is usually slow-cooked in a broth, and was a valuable food source to Native Americans.[ citation needed ] Early French Canadian Catholics considered beaver to be "four-legged fish" that could be eaten at Lent. [105]

Symbolism

Beaver sculpture over entrance to Canadian Parliament Building Beaver sculpture, Centre Block.jpg
Beaver sculpture over entrance to Canadian Parliament Building
Flag of Oregon (reverse) Flag of Oregon (reverse).svg
Flag of Oregon (reverse)

As one of the national symbols of Canada, [106] the North American beaver is depicted on the Canadian nickel. [106] This beaver was also featured on the first Canadian postage stamp, the Three Penny Beaver, which is considered the first postage stamp to show an animal instead of a head of state. [107] It is also the state animal of Oregon and New York of the United States, and a common school emblem for engineering schools, including the California Institute of Technology, the Massachusetts Institute of Technology, and the University of Alberta as well as the mascot for Oregon State University, Babson College, and the City College of New York. A beaver is featured prominently on the stamp and seal issued to Professional Engineers and Geoscientists by APEGA. It also appears on the back on the state flag of Oregon. The beaver also appears in the coats of arms of the Hudson's Bay Company, [108] University of Toronto, Wilfrid Laurier University, and the London School of Economics.

The beaver is also the symbol of the Royal Canadian Engineers both combat and civil.

Busy beaver is a term in theoretical computer science which refers to a terminating program of a given size that produces the most output possible.

Much of the early economy of New Netherland was based on the beaver fur trade. As such, the seal of New Netherland featured the beaver; likewise, the coats of arms of Albany, New York and New York City included the beaver.

See also

Related Research Articles

<span class="mw-page-title-main">Beaver</span> Genus of mammal

Beavers are large, semiaquatic rodents of the Northern Hemisphere. There are two existing species: the North American beaver and the Eurasian beaver. 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 a number of freshwater habitats, such as rivers, streams, lakes and ponds. They are herbivorous, consuming tree bark, aquatic plants, grasses and sedges.

<span class="mw-page-title-main">Castoridae</span> Family of mammals

Castoridae is a family of rodents that contains the two living species of beavers and their fossil relatives. A formerly diverse group, only a single genus is extant today, Castor. Two other genera of "giant beavers", Castoroides and Trogontherium, became extinct in the Late Pleistocene.

<span class="mw-page-title-main">Muskrat</span> Species of rodent

The muskrat or common muskrat is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America.

<span class="mw-page-title-main">Beaver Lake (King County, Washington)</span>

Beaver Lake is a 79-acre (0.3 km2) lake completely within the city limits of Sammamish, Washington. The Beaver Lake watershed is 1,043 acres (4.2 km2); the mean depth is 21 feet, and the maximum depth is 50 feet. Beaver Lake is actually a chain of one main and two smaller lakes, with the main lake getting the bulk of the recreation focus.

<span class="mw-page-title-main">Eurasian beaver</span> Species of beaver

The Eurasian beaver or European beaver is a species of beaver widespread across Eurasia, with a rapidly increasing population of at least 1.5 million in 2020. The Eurasian beaver was hunted to near-extinction for both its fur and castoreum, with only about 1,200 beavers in eight relict populations from France to Mongolia in the early 20th century. It has since been reintroduced into much of its former range and now lives from Western, Southern, Central and Eastern Europe, Scandinavia, Russia through China and Mongolia, with about half the population in Russia. It is listed as least concern on the IUCN Red List.

<span class="mw-page-title-main">North American river otter</span> Species of semi-aquatic mammal

The North American river otter, also known as the northern river otter and river otter, is a semiaquatic mammal that lives only on the North American continent throughout most of Canada, along the coasts of the United States and its inland waterways. An adult North American river otter can weigh between 5.0 and 14 kg. The river otter is protected and insulated by a thick, water-repellent coat of fur.

<span class="mw-page-title-main">Kickapoo River</span> River in Wisconsin, United States

The Kickapoo River is a 126-mile-long (203 km) tributary of the Wisconsin River in the state of Wisconsin, United States. It is named for the Kickapoo Indians who occupied Wisconsin before the influx of white settlers in the early 19th century.

<span class="mw-page-title-main">Castoreum</span> Fluid produced by beavers

Castoreum is a yellowish exudate from the castor sacs of mature beavers used in combination with urine to scent mark their territory.

<span class="mw-page-title-main">Sespe Creek</span> Stream in California

Sespe Creek is a stream, some 61 miles (98 km) long, in Ventura County, southern California, in the Western United States. The creek starts at Potrero Seco in the eastern Sierra Madre Mountains, and is formed by more than thirty tributary streams of the Sierra Madre and Topatopa Mountains, before it empties into the Santa Clara River in Fillmore.

<span class="mw-page-title-main">Aquatic mammal</span> Mammal that dwells partly or entirely in bodies of water

Aquatic mammals and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the European otter. They are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies greatly among species. Among freshwater taxa, the Amazonian manatee and river dolphins are completely aquatic and fully dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests, molts, and breeds on land; and the capybara and hippopotamus which are able to venture in and out of water in search of food.

<span class="mw-page-title-main">Beaver dam</span> Dam constructed by beavers

A beaver dam or beaver impoundment is a dam built by beavers; it creates a pond which protects against predators such as coyotes, wolves and bears, and holds their food during winter. These structures modify the natural environment in such a way that the overall ecosystem builds upon the change, making beavers a keystone species and ecosystem engineers. They build prolifically at night, carrying mud with their forepaws and timber between their teeth.

<span class="mw-page-title-main">San Pedro River (Arizona)</span> River in northern Sonora, Mexico, and southern Arizona, USA

The San Pedro River is a northward-flowing stream originating about 10 miles (16 km) south of the international border south of Sierra Vista, Arizona, in Cananea Municipality, Sonora, Mexico. The river starts at the confluence of other streams just east of Sauceda, Cananea. Within Arizona, the river flows 140 miles (230 km) north through Cochise County, Pima County, Graham County, and Pinal County to its confluence with the Gila River, at Winkelman, Arizona. It is the last major, undammed desert river in the American Southwest, and it is of major ecological importance as it hosts two-thirds of the avian diversity in the United States, including 100 species of breeding birds and almost 300 species of migrating birds.

<span class="mw-page-title-main">Flow device</span>

Flow devices are man-made solutions to beaver-related flooding problems. Flow devices are relatively cost-effective, low-maintenance solutions that regulate the water level of beaver dams and keep culverts open. Traditional solutions have involved the trapping and removal of all the beavers in an area. While this is sometimes necessary, it is typically a short-lived solution as beavers have rapidly recolonize suitable habitat.

<span class="mw-page-title-main">Beaver in the Sierra Nevada</span> Wildlife indigenous to California mountains

The North American beaver had a historic range that overlapped the Sierra Nevada in California. Before the European colonization of the Americas, beaver were distributed from the arctic tundra to the deserts of northern Mexico. The California Golden beaver subspecies was prevalent in the Sacramento and San Joaquin River watersheds, including their tributaries in the Sierra Nevada. Recent evidence indicates that beaver were native to the High Sierra until their extirpation in the nineteenth century.

<span class="mw-page-title-main">Weister Creek</span> River in Wisconsin, United States

Weister Creek is a stream, some 25 miles (40 km) long, in Vernon County in southwestern Wisconsin in the United States and is a tributary of the Kickapoo River. It lies in the Driftless Area which is characterized by hills and valleys apparently missed by the last glacial advance during the Pleistocene. Much of the lower half of Weister Creek is surrounded by wetlands and lies in the Kickapoo Valley Reserve.

<span class="mw-page-title-main">Trout Creek (Truckee River tributary)</span> River in California, United States

Trout Creek is a small tributary of the Truckee River draining about 5.1 square miles (13 km2) along the eastern crest of the Sierra Nevada. It originates east of Donner Ridge and north of Donner Lake in the Tahoe–Donner Golf Course and flows through the town of Truckee, California, to its confluence with the Truckee River in Nevada County, California, just west of Highway 267.

<span class="mw-page-title-main">Salt Creek (Little Calumet River tributary)</span> River in Indiana, United States

Salt Creek is a 24.0-mile-long (38.6 km) tributary of the East Arm Little Calumet River that begins south of Valparaiso in Porter County, Indiana and flows north until it joins the East Arm Little Calumet River just before it exits to Lake Michigan via the Port of Indiana-Burns Waterway.

<span class="mw-page-title-main">Eurasian beaver reintroduction</span> Effort in Europe to restore beaver range

The Eurasian beaver has been the successful subject of a century of official and unapproved species reintroduction programs in Europe and Asia. Beavers had been driven to the point of near extinction in Eurasia by humans trapping and hunting them for their meat, fur and castoreum. The reintroductions and conservation led in 2008, to the IUCN assessing the Eurasian beaver as being of "least concern" on its red list.

<span class="mw-page-title-main">Environmental impacts of beavers</span>

The beaver is a keystone species, increasing biodiversity in its territory through creation of ponds and wetlands. As wetlands are formed and riparian habitats enlarged, aquatic plants colonize newly available watery habitat. Insect, invertebrate, fish, mammal, and bird diversities are also expanded. Effects of beaver recolonization on native and non-native species in streams where they have been historically absent, particularly dryland streams, is not well-researched.

<span class="mw-page-title-main">Beavers in Southern Patagonia</span>

The North American beaver is an invasive species in Tierra del Fuego, at the southern end of Patagonia. Tierra del Fuego is a large island encompassing parts of Chile and Argentina, so that policies and actions to control the species have mainly been binational. The beavers were introduced to the area in 1946 in an effort by the Argentine government to establish a fur trade in the region. Since then, the beavers have spread throughout most of Tierra del Fuego and have also been seen on the Brunswick Peninsula of mainland Chile. When the fur trade failed to establish, the beavers became problematic and the two governments agreed to intervene to eradicate them.

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