Beaver

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Beaver
Temporal range: 24–0  Ma
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Late Miocene  – Recent
American Beaver.jpg
North American beaver (Castor canadensis)
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Castoridae
Subfamily: Castorinae
Genus:Castor
Linnaeus, 1758
Species

C. fiber – Eurasian beaver
C. canadensis – North American beaver
C. californicus

Contents

The beaver (genus Castor) is a large, primarily nocturnal, semiaquatic rodent. Castor includes two extant species, the North American beaver (Castor canadensis) (native to North America) and Eurasian beaver ( Castor fiber ) (Eurasia). [1] Beavers are known for building dams, canals, and lodges (homes). They are the second-largest rodent in the world (after the capybara). Their colonies create one or more dams to provide still, deep water to protect against predators, and to float food and building material. The North American beaver population was once more than 60 million, but as of 1988 was 6–12 million. This population decline is the result of extensive hunting for fur, for glands used as medicine and perfume, and because the beavers' harvesting of trees and flooding of waterways may interfere with other land uses. [2]

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

Rodent Diverse order of mammals

Rodents are mammals of the order Rodentia, which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents ; they are found in vast numbers on all continents except Antarctica. They are the most diversified mammalian order and live in a variety of terrestrial habitats, including human-made environments.

North American beaver species of mammal

The North American beaver is one of two extant beaver species. It is native to North America and introduced to Patagonia in South America and some European countries. In the United States and Canada, the species is often referred to simply as "beaver", though this causes some confusion because another distantly related rodent, Aplodontia rufa, is often called the "mountain beaver". Other vernacular names, including American beaver and Canadian beaver, distinguish this species from the other extant beaver species, Castor fiber, which is native to Eurasia. The North American beaver is an official animal symbol of Canada and is the official state mammal of Oregon.

General

Beavers, along with pocket gophers and kangaroo rats, are castorimorph rodents, a suborder of rodents mostly restricted to North America. Although just two closely related species exist today, beavers have a long fossil history in the Northern Hemisphere beginning in the Eocene, and many species of giant beaver existed until quite recently, such as Trogontherium in Europe, and Castoroides in North America.

Heteromyidae family of mammals

Heteromyidae is a family of rodents consisting of kangaroo rats, kangaroo mice, pocket mice and spiny pocket mice. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the genus Heteromys are also found in forests and their range extends down as far as northern South America. They feed mostly on seeds and other plant parts, which they carry in their fur-lined cheek pouches to their burrows.

Castorimorpha suborder of mammals

Castorimorpha is the suborder of rodents containing the beavers, the pocket gophers, and the kangaroo rats and kangaroo mice.

The Eocene Epoch, lasting from 56 to 33.9 million years ago, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the Grande Coupure or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are slightly uncertain.

A beaver using its teeth to cut down a tree American Beaver, tree cutting.jpg
A beaver using its teeth to cut down a tree

Beavers are known for their natural trait of building dams on rivers and streams, and building their homes (known as "lodges") in the resulting pond. Beavers also build canals to float building materials that are difficult to haul over land. [3] [4] They use powerful front teeth to cut trees and other plants that they use both for building and for food. In the absence of existing ponds, beavers must construct dams before building their lodges. First they place vertical poles, then fill between the poles with a crisscross of horizontally placed branches. They fill in the gaps between the branches with a combination of weeds and mud until the dam impounds sufficient water to surround the lodge.

They are known for their alarm signal: when startled or frightened, a swimming beaver will rapidly dive while forcefully slapping the water with its broad tail, audible over great distances above and below water. This serves as a warning to beavers in the area. Once a beaver has sounded the alarm, nearby beavers will dive and may not reemerge for some time. Beavers are slow on land, but are good swimmers, and can stay under water for as long as 15 minutes.

Beavers do not hibernate, but store sticks and logs in a pile in their ponds, eating the underbark. Some of the pile is generally above water and accumulates snow in the winter. This insulation of snow often keeps the water from freezing in and around the food pile, providing a location where beavers can breathe when outside their lodge.

The fore foot, hind foot, and tail of a beaver. The hind feet of beavers are webbed. Picture Natural History - No 40 41 42 - Beaver feet and tail.png
The fore foot, hind foot, and tail of a beaver. The hind feet of beavers are webbed.

Beavers have webbed hind-feet, and a broad, scaly tail. They have poor eyesight, but keen senses of hearing, smell, and touch. A beaver's teeth grow continuously so they will not be worn down by chewing on wood. [5] Their four incisors are composed of hard orange enamel on the front and a softer dentin on the back. The chisel-like ends of incisors are maintained by their self-sharpening wear pattern. The enamel in a beaver's incisors contains iron and is more resistant to acid than enamel in the teeth of other mammals. [6]

Webbed foot animal feet with non-pathogenic interdigital webbing

The webbed foot is a specialized limb present in a variety of vertebrates to aid in locomotion. This adaptation is primarily found in semi-aquatic species, and has convergently evolved many times across vertebrate taxa. It likely arose from mutations in developmental genes that normally cause tissue between the digits to apoptose. These mutations were beneficial to many semi-aquatic animals because the increased surface area from the webbing allowed for more swimming propulsion and swimming efficiency, especially in surface swimmers. The webbed foot also has enabled other novel behaviors like escape responses and mating behaviors.

Dentin one of the four major components of teeth

Dentin or dentine is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By volume, 45% of dentin consists of the mineral hydroxylapatite, 33% is organic material, and 22% is water. Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel. Dentin rates approximately 3 on the Mohs scale of mineral hardness. There are two main characteristics which distinguish dentin from enamel: firstly, dentin forms throughout life; secondly, dentin is sensitive.

Beavers continue to grow throughout their lives. Adult specimens weighing over 25 kg (55 lb) are not uncommon. Females are as large as or larger than males of the same age, which is uncommon among mammals. Beavers live up to 24 years of age in the wild.

Mammal Animals with milk-producing glands

Mammals are vertebrate animals constituting the class Mammalia, and characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, from which they diverged in the late Triassic, 201–227 million years ago. There are around 5,450 species of mammals. The largest orders are the rodents, bats and Soricomorpha. The next three are the Primates, the Cetartiodactyla, and the Carnivora.

Etymology

The English word "beaver" comes from the Old English word beofor or befer (recorded earlier as bebr), which in turn sprang from the Proto-Germanic root *bebruz. Cognates in other Germanic languages include the Old Saxon bibar, the Old Norse bjorr, the Middle Dutch and Dutch bever, the Low German bever, the Old High German bibar and the Modern German Biber. The Proto-Germanic word in turn came from the Proto-Indo-European (PIE) word *bhebhrus, a reduplication of the PIE root *bher-, meaning "brown" or "bright", whose own descendants now include the Lithuanian bebras and the Czech bobr, as well as the Germanic forms. [7]

Old English, or Anglo-Saxon, is the earliest historical form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers probably in the mid-5th century, and the first Old English literary works date from the mid-7th century. After the Norman conquest of 1066, English was replaced, for a time, as the language of the upper classes by Anglo-Norman, a relative of French. This is regarded as marking the end of the Old English era, as during this period the English language was heavily influenced by Anglo-Norman, developing into a phase known now as Middle English.

Proto-Germanic language Ancestor of the Germanic languages

Proto-Germanic is the reconstructed proto-language of the Germanic branch of the Indo-European languages.

Cognate word that has a common etymological origin

In linguistics, cognates are words that have a common etymological origin. Cognates are often inherited from a shared parent language, but they may also involve borrowings from some other language. For example, the English words dish and desk and the German word Tisch ("table") are cognates because they all come from Latin discus, which relates to their flat surfaces. Cognates may have evolved similar, different or even opposite meanings, but in most cases there are some similar sounds or letters in the words, in some cases appearing to be dissimilar. Some words sound similar, but do not come from the same root; these are called false cognates, while some are truly cognate but differ in meaning; these are called false friends.

Species

Skulls of a Eurasian beaver and a North American beaver. Castor fiber vs. Castor canadensis skulls.jpg
Skulls of a Eurasian beaver and a North American beaver.

The North American and Eurasian beavers are the only extant members of the family Castoridae, contained within the monotypic genus, Castor. Genetic research has shown the modern European and North American beaver populations to be distinct species and that hybridization is unlikely. Although superficially similar to each other, there are several important differences between the two species. Eurasian beavers tend to be slightly larger, with larger, less rounded heads, longer, narrower muzzles, thinner, shorter and lighter underfur, narrower, less oval-shaped tails and shorter shin bones, making them less capable of bipedal locomotion than the North American species. Eurasian beavers have longer nasal bones than their North American cousins, with the widest point being at the end of the snout for the former, and in the middle for the latter. The nasal opening for the Eurasian species is triangular, unlike that of the North American race, which is square. The foramen magnum is rounded in the Eurasian beaver and triangular in the North American. The anal glands of the Eurasian beaver are larger and thin-walled with a large internal volume compared to that of the North American species. The guard hairs of the Eurasian beaver have a longer hollow medulla at their tips. Fur colour is also different. Overall, 66% of Eurasian beavers have pale brown or beige fur, 20% have reddish brown, nearly 8% are brown and only 4% have blackish coats. In North American beavers, 50% have pale brown fur, 25% are reddish brown, 20% are brown and 6% are blackish. [8]

The two species are not genetically compatible. North American beavers have 40 chromosomes, while Eurasian beavers have 48. 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 a single stillborn kit. These factors make interspecific breeding unlikely in areas where the two species' ranges overlap. [8]

Eurasian beaver

A Eurasian beaver feeding. Castor fiber eating in Eskilstuna, Sweden.jpg
A Eurasian beaver feeding.

The Eurasian beaver (Castor fiber) was hunted nearly to extinction in Europe, both for fur and for castoreum , a secretion from its scent gland believed to have medicinal properties. However, the beaver is now being re-introduced throughout Europe. Several thousand live on the Elbe and the Rhône and in parts of Scandinavia. A thriving community lives in northeast Poland, and the Eurasian beaver also returned to the Morava River banks in Slovakia and the Czech Republic. They have been reintroduced in Scotland (Knapdale), [9] Bavaria, Austria, Netherlands, Serbia (Zasavica bog), Denmark (West Jutland) and Bulgaria and are spreading to new locations. The beaver became extinct in Great Britain in the sixteenth century: Giraldus Cambrensis reported in 1188 (Itinerarium ii.iii) that it was to be found only in the Teifi in Wales and in one river in Scotland, though his observations are clearly second hand. In 2001, Kent Wildlife Trust successfully introduced a family of beavers at Ham Fen, the last remaining ancient fenland in the county close to the town of Sandwich; these are now established and are breeding. In October 2005, six Eurasian beavers were reintroduced to Britain in Lower Mill Estate in Gloucestershire; in July 2007 a colony of four Eurasian beavers was established at Martin Mere in Lancashire, [10] and a small population of probably Eurasian beavers is being monitored in Devon. [11] A trial re-introduction occurred in Scotland in May 2009. Feasibility studies for a reintroduction to Wales are at an advanced stage and a preliminary study for a reintroduction of beavers to the wild in England has recently been published. [12] [13]

North American beaver

A North American beaver shortly after leaving the water. Castor canadensis1.jpg
A North American beaver shortly after leaving the water.

The North American beaver (Castor canadensis), also called the Canadian beaver (which is also the name of a subspecies), American beaver, or simply beaver in North America, is native to Canada, much of the United States and the states of Sonora and Chihuahua in northern Mexico. [14] [15] [16] This species was introduced to the Argentine and Chilean Tierra del Fuego, as well as Finland, France, Poland and Russia. [17] [18]

The North American beavers prefer the (inner) bark of aspen and poplar but will also take birch, maple, willow, alder, black cherry, red oak, beech, ash, hornbeam and occasionally pine and spruce. [19] They will also eat cattails, water lilies and other aquatic vegetation, especially in the early spring (and contrary to widespread belief, [20] they do not eat fish).

These animals are often trapped for their fur. During the early 19th century, trapping eliminated this animal from large portions of its original range. Beaver furs were used to make clothing and top-hats. Much of the early exploration of North America was driven by the quest for this animal's fur. [21] [22] [23] Native peoples and early settlers also ate this animal's meat. The Federal Lacey Act was passed by the US Fish and Wildlife Service in 1900 which forbade any take of wildlife or plants in violation of Indian, State or foreign law. [24] Through trap and transfer and habitat conservation, beavers made a nearly complete recovery by the 1940s.The current beaver population has been estimated to be 10 to 15 million; one estimate claims there may have been at one time as many as 90 million. [25]

Habitat

A beaver dam at the edge of a stream. Beavers generally live in the riparian zone, an area between the land and a river or stream. Beaver Dam.jpg
A beaver dam at the edge of a stream. Beavers generally live in the riparian zone, an area between the land and a river or stream.

The primary habitat of the beaver is the riparian zone, inclusive of stream bed. The actions of beavers for hundreds of thousands of years [26] in the Northern Hemisphere have kept these watery systems healthy and in good repair. However, some beavers inhabit the intertidal zone in river estuaries, building dams to trap high tides in a beaver pond for similar purposes. [27] [28]

The beaver works as a keystone species in an ecosystem by creating wetlands that are used by many other species. Next to humans, no other extant animal appears to do more to shape its landscape. [29] Beavers potentially even affect climate change. [30]

Beavers fell trees for several reasons. They fell large mature trees, usually in strategic locations, to form the basis of a dam, but European beavers tend to use small diameter (<10 cm) trees for this purpose. Beavers fell small trees, especially young second-growth trees, for food.

Broadleaved trees re-grow as a coppice, providing easy-to-reach stems and leaves for food in subsequent years. Ponds created by beavers can also kill some tree species by drowning, but this creates standing dead wood, which is very important for a wide range of animals and plants. [31]

Dams

Beaver dam enlargement
Beaver dam - geograph.org.uk - 1452003.jpg
September 2009
Beaver dam - four months on - geograph.org.uk - 1623430.jpg
December 2009
Images of a beaver dam over a four month period. Beavers are able to enlarge their dams quickly.

Beaver dams are created as a protection against predators, such as coyotes, wolves and bears, and to provide easy access to food during winter. Beavers always work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth. Because of this, destroying a beaver dam without removing the beavers is difficult, especially if the dam is downstream of an active lodge. Beavers can rebuild such primary dams overnight, though they may not defend secondary dams as vigorously. Beavers may create a series of dams along a river.

Lodges

The ponds created by well-maintained dams help isolate the beavers' homes, which are called lodges. These are created from severed branches and mud. The beavers cover their lodges late each autumn with fresh mud, which freezes when frosts arrive. The mud becomes almost as hard as stone, thereby preventing wolves and wolverines from penetrating the lodge.

This diagram depicts the parts of a beaver lodge. A. vent, B. feeding chamber, C. nesting chamber, D. entrance BeaverLodgeDiagram.svg
This diagram depicts the parts of a beaver lodge. A. vent, B. feeding chamber, C. nesting chamber, D. entrance

The lodge has underwater entrances, which makes entry nearly impossible for any other animal, although muskrats have been seen living inside beaver lodges with the beavers who made them. [32] Only a small amount of the lodge is actually used as a living area. Beavers dig out their dens with underwater entrances after they finish building the dams and lodge structures. There are typically two dens within the lodge, one for drying off after exiting the water and another, drier one, in which the family lives.

Beaver lodges are constructed with the same materials as the dams, with little order or regularity of structure. They seldom house more than four adults and six to eight juveniles. Some larger lodges have one or more partitions, but these are only posts of the main building left by the builders to support the roof. Usually, the dens have no connection with each other except by water.

When the ice breaks up in spring, beavers usually leave their lodges and roam until just before autumn, when they return to their old lodges and gather their winter stock of wood. They seldom begin to repair the lodges until the frost sets in, and rarely finish the outer coating until the cold becomes severe. When they erect a new lodge, they fell the wood early in summer but seldom begin building until nearly the end of August. [33]

Water quality and beavers

A beaver dam at Mill Creek. Beaver dams are able to remove sediment, and pollutants from waterways. Lundy Canyon Beaver Dam.jpg
A beaver dam at Mill Creek. Beaver dams are able to remove sediment, and pollutants from waterways.

Beaver ponds, and the wetlands that succeed them, remove sediments and pollutants from waterways, including total suspended solids, total nitrogen, phosphates, carbon and silicates. [34] [35]

The term "beaver fever" is a misnomer coined by the American press in the 1970s, following findings that the parasite Giardia lamblia , which causes Giardiasis, is carried by beavers. However, further research has shown that many animals and birds carry this parasite, and the major source of water contamination is other humans. [36] [37] [38] Norway has many beavers but has not historically had giardia, and New Zealand has giardia but no beaver. Recent concerns point to domestic animals as a significant vector of giardia, with young calves in dairy herds testing as high as 100% positive for giardia. [39] In addition, fecal coliform and streptococci bacteria excreted into streams by grazing cattle have been shown to be reduced by beaver ponds, where the bacteria are trapped in bottom sediments. [40]

Urban beavers in North America

Wire mesh fences installed around trees in High Park, Toronto. Cities in Canada occasionally use mesh fences to prevent beaver damage. Beaver fences High Park.jpg
Wire mesh fences installed around trees in High Park, Toronto. Cities in Canada occasionally use mesh fences to prevent beaver damage.

Beaver populations in Canadian cities have seen a resurgence in numbers in the decades since the decline of the fur trade. [42] [43] [44] In 2016, approximately 200 beavers live within the city limits of Calgary, while an estimated 100 beavers live in Winnipeg. [45] In the same year, it was estimated that several dozen beavers live within the city limits of Vancouver. [45] Toronto does not keep count of its local beaver population, [45] although an estimate from 2001 places its local beaver population at several hundred. [44]

Several cities in the United States have seen the reintroduction of beavers within their city limits. Beavers were trapped to near extirpation and had not been seen in New York City since the early 1800s. [46] After 200 years, a beaver has returned to New York City, making its home along the Bronx River. [47] In Chicago, several beavers have returned and made a home near the Lincoln Park's North Pond. The "Lincoln Park beaver" has not been as well received by the Chicago Park District and the Lincoln Park Conservancy, which was concerned over damage to trees in the area. In March 2009, they hired an exterminator to remove a beaver family using live traps, and accidentally killed the mother when she got caught in a snare and drowned. [48]

Outside San Francisco, in downtown Martinez, California, a male and female beaver arrived in Alhambra Creek in 2006. [49] The Martinez beavers built a dam 30 feet wide and at one time six feet high, and chewed through half the willows and other creekside landscaping the city planted as part of its $9.7 million 1999 flood-improvement project. When the city council wanted to remove the beavers because of fears of flooding, local residents organized to protect them, forming an organization called "Worth a Dam". [50]

As an 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 from northern Manitoba in Canada to the island of Tierra Del Fuego in southern Chile and Argentina, for commercial fur production. However, the project failed and the beavers, ten pairs, were released into the wild. Having no natural predators in their new environment, they quickly spread throughout the island, and to other islands in the region, reaching a number of 100,000 individuals within just 50 years. They are now considered a serious invasive species in the region, due to their massive destruction of forest trees, and efforts are being made for their eradication. [51] The drastically different ecosystem has led to substantial environmental damage, as the ponds created by the beavers have no ecological purpose (wetlands do not form there as they do in the beavers' native territory) and there are no native, large predators.[ citation needed ] They have also been found to cross salt water to islands northward; a possible encroachment on the mainland has naturalists highly concerned.

In contrast, areas with introduced beaver were associated with increased populations of native puye fish (Galaxias maculatus), whereas the exotic brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss) had negative effects on native stream fishes in the Cape Horn Biosphere Reserve, Chile. [52]

Beavers are classed as a "prohibited new organism" under New Zealand's Hazardous Substances and New Organisms Act 1996, preventing them from legally being imported into the country. [53]

Social behavior

Family life

A pair of beavers. Beavers are monogamous, with a beaver's social organization consisting of a pair of adults, and its offspring. Beaver 2.jpg
A pair of beavers. Beavers are monogamous, with a beaver's social organization consisting of a pair of adults, and its offspring.

The basic units of beaver social organization are families consisting of an adult male and adult female in a monogamous pair and their kits and yearlings. [54] Beaver families can have as many as ten members in addition to the monogamous pair. Groups this size or close to this size build more lodges to live in while smaller families usually need only one. [54] However, large families in the Northern Hemisphere have been recorded living in one lodge. Beaver pairs mate for life; however, if a beaver's mate dies, it will partner with another one. Extra-pair copulations also occur. [54] In addition to being monogamous, both the male and female take part in raising offspring. They also both mark and defend the territory and build and repair the dam and lodge. [54] When young are born, they spend their first month in the lodge and their mother is the primary caretaker while their father maintains the territory. In the time after they leave the lodge for the first time, yearlings will help their parents build food caches in the fall and repair dams and lodges. Still, adults do the majority of the work and young beavers help their parents for reasons based on natural selection rather than kin selection. They are dependent on them for food and for learning life skills. [54] Young beavers spend most of their time playing but also copy their parents' behavior. However, while copying behavior helps imprint life skills in young beavers, it is not necessarily immediately beneficial for parents as the young beaver do not perform the tasks as well as the parents. [54]

A beaver family, with the centre pair grooming one another. Beaver family upper Los Gatos Creek 2008 Mercury Freedom.jpg
A beaver family, with the centre pair grooming one another.

Older offspring, which are around two years old, may also live in families and help their parents. In addition to helping build food caches and repairing the dam, two-year-olds will also help in feeding, grooming and guarding younger offspring. [54] Beavers also practice alloparental care, in which an older sibling may take over the parenting duties if the original parents die or are otherwise separated from them. This behavior is common and is seen in many other animal species, such as the elephant and fathead minnow. [55] While these helping two-year-olds help increase the chance of survival for younger offspring, they are not essential for the family, and two-year-olds stay and help their families only if there is a shortage of resources in times of food shortage, high population density, or drought. [54] When beavers leave their natal territories, they usually do not settle far. [56] Beavers can recognize their kin by detecting differences in anal gland secretion composition using their keen sense of smell. [57] Related beavers share more features in their anal gland secretion profile than unrelated beavers. [57] Being able to recognize kin is important for beaver social behavior, and it causes more tolerant behavior among neighboring beavers. [56]

Territories and spacing

A beaver atop its dam. AmericanBeaver.JPG
A beaver atop its dam.

Beavers maintain and defend territories, which are areas for feeding, nesting and mating. [54] They invest much energy in their territories, building their dams and becoming familiar with the area. [58] Beavers mark their territories by constructing scent mounts made of mud, debris and castoreum, [59] a urine based substance excreted through the beavers castor sacs between the pelvis and base of the tail. [58] These scent mounts are established on the border of the territory. [59] Once a beaver detects another scent in its territory, finding the intruder takes priority, even over food. [59] Because they invest so much energy in their territories, beavers are intolerant of intruders and the holder of the territory is more likely to escalate an aggressive encounter. [58] These encounters are often violent. To avoid such situations, a beaver marks its territory with as many scent mounds as possible, signaling to intruders that the territory holder has enough energy to maintain its territory and is thus able to put up a good defense. As such, territories with more scent mounts are avoided more often than ones with fewer mounts. [58] Scent marking increases in August during the dispersal of yearlings, in an attempt to prevent them from intruding on territories. [58] Beavers also exhibit a behavior known as the "dear enemy effect". A territory-holding beaver will investigate and become familiar with the scents of its neighbors. [56] As such they respond less aggressively to intrusions by their territorial neighbours than those made by non-territorial floaters or "strangers". [56]

Occurrences of beaver aggression, however, have been reported. In April 2013, an angler, near Minkovichi in the Brest region of Belarus, died after being bitten twice on the leg by a wild Eurasian beaver. [60]

Commercial uses

Depiction of a beaver hunt from a medieval bestiary. Beaver testicles has historically been an item of trade, for use in traditional medicine. Beaverbollocks.jpg
Depiction of a beaver hunt from a medieval bestiary. Beaver testicles has historically been an item of trade, for use in traditional medicine.

Both beaver testicles and castoreum, a bitter-tasting secretion with a slightly fetid odor contained in the castor sacs of male or female beaver, have been articles of trade for use in traditional medicine. Yupik medicine used dried beaver testicles like willow bark to relieve pain. Dried beaver testicles were also used as contraception. [61] Beaver testicles were used as medicine in Iraq and Iran during the tenth to nineteenth century. [62] Aesop's Fables describes beavers chewing off their testicles to preserve themselves from hunters, which is not possible because the beaver's testicles are inside its body. This belief, also recorded by Pliny the Elder, persisted in medieval bestiaries. [63]

European beavers ( Castor fiber ) were eventually hunted nearly to extinction in part for the production of castoreum, which was used as an analgesic, anti-inflammatory, and antipyretic. Castoreum was described in the 1911 British Pharmaceutical Codex for use in dysmenorrhea and hysterical conditions (i.e. pertaining to the womb), for raising blood pressure and increasing cardiac output. The activity of castoreum has been credited to the accumulation of salicin from willow trees in the beaver's diet, which is transformed to salicylic acid and has an action very similar to aspirin. [64] Castoreum continues to be used in perfume production. [65]

Castoreum can be used as an enhancer of vanilla, strawberry and raspberry flavorings. It is sometimes added to frozen dairy, gelatins, candy, and fruit beverages. Due to the difficulty and expense in obtaining castoreum, it is very rarely used in common food products. [65] [66]

Much of the early European exploration and trade of Canada was based on the quest for beaver. [67] The most valuable part of a beaver is its inner fur whose many minute barbs make it excellent for felting, especially for hats. In Canada a "made beaver" or castor gras that a native had worn or slept on was more valuable than a fresh skin since this tended to wear off the outer guard hairs.[ citation needed ]

Trapping

A beaver pelt. Beaver pelts was the driving force of the North American fur trade. BeaverPelt (5118396762).jpg
A beaver pelt. Beaver pelts was the driving force of the North American fur trade.

Beavers have been trapped for millennia, and this continues to this day. [68] Beaver pelts were used for barter by Native Americans in the 17th century to gain European goods. They were then shipped back to Great Britain and France where they were made into clothing items. Widespread hunting and trapping of beavers led to their endangerment. Eventually, the fur trade declined due to decreasing demand in Europe and the takeover of trapping grounds to support the growing agriculture sector. A small resurgence in beaver trapping has occurred in some areas where there is an over-population of beaver; trapping is done when the fur is of value, and the remainder of the animal may be used as feed. In the 1976/1977 season, 500,000 beaver pelts were harvested in North America. [69]

In culture

In wider culture, the beaver is famed for its industriousness and its building skills. The English verb "to beaver" means to work hard and constantly.

Beverly or Beverley, a placename found at various locations in the English-speaking world and also commonly used as a first name, derives from Old English, combining the words befer ("beaver") and leah ("clearing").

The show Happy Tree Friends features Toothy and Handy who are beavers.

The animated Nickelodeon show The Angry Beavers features Daggett and Norbert.

The anthropomorphic Mr. and Mrs. Beaver have an important role in the plot of The Lion, the Witch and the Wardrobe , first part of C.S.Lewis' The Chronicles of Narnia.

The first Redwall book features an unnamed beaver who helps Constance the badger build a bow, the only one ever seen before the books shifted to focus on animals commonly native to the British Isles.

The 2014 American horror comedy film Zombeavers , directed by Jordan Rubin, follows a group of college students on a camping trip that are attacked by a swarm of zombie beavers.

As an emblem

National

Beaver sculpture over entrance to Canadian Parliament Building. Beaver sculpture, Centre Block.jpg
Beaver sculpture over entrance to Canadian Parliament Building.

The importance of the beaver in the development of Canada through the fur trade led to its official designation as the national animal in 1975. The animal has long been associated with Canada, appearing on the coat of arms of the Hudson's Bay Company in 1678. [70] It is depicted on the Canadian five-cent piece and was on the first pictorial postage stamp issued in the Canadian colonies in 1849 (the so-called "Three-Penny Beaver"). As a national symbol, the beaver was chosen to be the mascot of the 1976 Summer Olympics held in Montreal with the name "Amik" ("beaver" in Ojibwe). The beaver is also the symbol of many units and organizations within the Canadian Forces, such as on the cap badges of the Royal 22e Régiment, the Calgary Highlanders, the Royal Westminster Regiment and the Canadian Military Engineers. Toronto Police Services, London Police Service, Canadian Pacific Railway Police Service and Canadian Pacific Railway bear the beaver on their crest or coat of arms.

Others

A beaver is used in the logo for Parks Canada, a federal agency of Canada. Parks Parcs Canada beaver logo.jpg
A beaver is used in the logo for Parks Canada, a federal agency of Canada.

Others who have used the beaver in their company or organizational symbol or as their mascot include:

In dietary law

In the 17th century, based on a question raised by the Bishop of Quebec, the Roman Catholic Church ruled that beavers are fish (beaver flesh was a part of the Yuko [72] indigenous peoples' diet, prior to the Europeans' arrival [73] ) for purposes of dietary law. Therefore, the general prohibition on the consumption of meat on Fridays did not apply to beaver meat. [74] [75] [76] The legal basis for the decision probably rests with the Summa Theologica of Thomas Aquinas, which bases animal classification as much on habit as anatomy. [77] This is similar to the Church's classification of other semi-aquatic rodents, such as the capybara and muskrat. [78] [79]

Related Research Articles

Castoridae Family of mammals

The family Castoridae contains the two living species of beavers and their fossil relatives. This was once a highly diverse group of rodents, but is now restricted to a single genus, Castor.

Wood Buffalo National Park national park in Canada

Wood Buffalo National Park is the largest National Park of Canada at 44,807 km2 (17,300 sq mi). It is located in northeastern Alberta and the southern Northwest Territories. Larger in area than Switzerland, it is the second-largest national park in the world. The park was established in 1922 to protect the world's largest herd of free roaming wood bison, currently estimated at more than 5,000. It is one of two known nesting sites of whooping cranes.

Muskrat species of mammal

The muskrat, the only species in genus Ondatra and tribe Ondatrini, is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitats. It has important effects on the ecology of wetlands, and is a resource of food and fur for humans.

Eurasian beaver Species of beaver

The Eurasian beaver or European beaver is a beaver species that was once widespread in Eurasia, but was hunted to near-extinction for both its fur and castoreum. At the turn of the 20th century, only about 1,200 beavers survived in eight relict populations in Europe and Asia. It has been reintroduced to much of its former range, and now occurs from Spain, Central Europe, Great Britain and Scandinavia to a few regions in China and Mongolia. It is listed as Least Concern on the IUCN Red List, as it recovered well in most of Europe. It is extinct in Portugal, Moldova, and Turkey.

North American river otter one of the only two species of otter in North America, along with the sea otter

The North American river otter, also known as the northern river otter or the common otter, is a semiaquatic mammal endemic to the North American continent found in and along its waterways and coasts. 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.

Kickapoo River river in the United States of America

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.

Castoreum chemical substance

Castoreum is a yellowish exudate from the castor sacs of the mature North American beaver and the European beaver.

<i>Castoroides</i> genus of mammals

Castoroides, or giant beaver, is an extinct genus of enormous beavers that lived in North America during the Pleistocene. C. leiseyorum and its northern sister species C. ohioensis, were the largest beavers to ever exist.

Trapping device to remotely catch an animal

Animal trapping, or simply trapping, is the use of a device to remotely catch an animal. Animals may be trapped for a variety of purposes, including food, the fur trade, hunting, pest control, and wildlife management.

Beaver dam dam constructed by beavers

Beaver dams or beaver impoundments are dams built by beavers to provide ponds as protection against predators such as coyotes, wolves, and bears, and to provide easy access to 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. Beavers work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth.

Martinez, California beavers

The Martinez beavers are a family of North American beavers living in Alhambra Creek in downtown Martinez, California. Best known as the longtime home of famed 19th/20th-century naturalist John Muir, Martinez has become a national example of urban stream restoration utilizing beavers as ecosystem engineers.

Alhambra Creek river in the United States of America

Alhambra Creek is a stream in Contra Costa County, in the East Bay region of the San Francisco Bay Area in northern California.

Flow device

Flow devices are man-made solutions to beaver-related flooding problems. 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 beaver populations have made a remarkable comeback in the United States and rapidly recolonize suitable habitat. In fact, a 2006 survey found that trapping as a solution to beaver problems had a 79% failure rate within two years due to resettlement by new beavers. Flow devices are relatively cost-effective, low-maintenance solutions that regulate the water level of beaver dams and keep culverts open. A 2006 study by the Virginia Department of Transportation found that for every $1 spent on flow-device installation relative to historical preventive maintenance, road repairs, and beaver population control activities, $8 was saved, for a return on investment of nearly 8:1.

Beaver in the Sierra Nevada

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.

Weister Creek stream in Vernon County, Wisconsin, United States of America

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.

Trout Creek (Truckee River tributary) river in California, United States of America

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.

Beaver eradication in Tierra del Fuego

The eradication of the North American beaver in Tierra del Fuego is being attempted by the governments of Chile and Argentina in this area at the southernmost tip of South America. The non-native species was introduced in 1946 as a potential source of commercial fur trading. When the fur trade industry was unsuccessful, however, the beavers became problematic and the governments agreed to intervene. A June 2011 NPR report stated that the beavers have caused millions of dollars in damages. According to Nature, this plan is the largest eradication project ever attempted.

Taylor Creek (Lake Tahoe) river in the United States of America

Taylor Creek is a 2.2-mile-long (3.5 km) northward-flowing stream originating in the Fallen Leaf Lake and culminating at Baldwin Beach at Lake Tahoe, about 1 mile (1.6 km) west of Camp Richardson in El Dorado County, California.

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Further reading