Beaver

Jai Ganesh · Yesterday 21:53:07

Beaver

Gist

Beavers are famous for being "ecosystem engineers," known for building dams with sticks, mud, and rocks to create ponds, which reshapes landscapes, controls water flow, prevents erosion, and creates vital wetland habitats for many species. They are also known for their continuously growing, iron-rich orange teeth, paddle-like tails used for signaling and balance, thick waterproof fur, industrious nature (hence "busy as a beaver"), and for being the national symbol of Canada.

How strong is a beaver's bite?

When a beaver decides to bite it can unleash 180 pounds of pressure per square inch. To give you an idea of what that means… It takes about 160 pounds of pressure to break a human femur (the largest bone in your body). This is how they take down trees we would need chain saws for.

Summary

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 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, forming ponds, and lodges (usually built in ponds) serve as shelters. Their infrastructure creates wetlands used by many other species, and because of their effect on other organisms in the ecosystem, beavers are considered a keystone species. Adult males and females live in 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 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 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.

Details

A beaver, (genus Castor), is either of two species of amphibious rodents native to North America, Europe, and Asia. Beavers are the largest rodents in North America and Eurasia and the second largest rodents worldwide. Their bodies extend up to 80 cm (31 inches) long and generally weigh 16–30 kg (35–66 pounds); however, beavers continue to grow throughout their life, and the heaviest beavers can weigh more than 50 kg (110 pounds). The distinctive tail is scaly, flat, and paddle-shaped and measures up to 45 cm (about 18 inches) long and 13 cm (5 inches) wide. Living in streams, rivers, marshes, and ponds and on the shorelines of large lakes, beavers construct dams of branches, stones, and mud, forming ponds that often cover many hectares. Ecologists often refer to beavers as “ecosystem engineers” because of their ability to alter the landscapes in which they live.

Beavers have short legs and a stout body with a small, broad, and blunt head. Massive chisel-shaped incisor teeth have orange outer enamel because iron has replaced calcium, and this makes them stronger than most rodent incisors. Upon submergence, folds of skin (valves) close the nostrils and the stubby rounded ears, and the eyes are protected by a membrane that keeps water out (nictitating membrane). The fur-lined lips close behind the incisors, blocking water from the mouth and lungs and allowing the animal to cut, peel, and carry branches underwater. Small front feet with five clawed digits dexterously manipulate food. The hind feet are quite large, and the five digits are connected by webbing, which makes them useful as paddles for propulsion underwater. Claws of the second hind digits are split and have serrated edges used for grooming the fur.

Fur consists of a grayish to brown layer of short, fine, and dense underfur that keeps water from reaching the skin. Over this layer are long, coarse, glossy guard hairs ranging in colour from yellowish brown through reddish brown to black; underparts of the animal are paler. Both sexes possess castor glands that exude a musky secretion (castoreum), which is deposited on mud or rocks to mark territorial boundaries. Anal glands secrete oil through skin pores to hair roots. From there it is distributed with the front feet and grooming claws over the whole body to keep the fur sleek, oily, and water-repellent.

Beavers are colonial and primarily nocturnal. Their characteristically dome-shaped island lodges are built of branches plastered with mud. In marshes, lakes, and small rivers, beavers may instead construct bank lodges, and in large rivers and lakes they excavate bank dens with an underwater entrance beneath tree roots or overhanging ledges. Each lodge is occupied by an extended family group of up to eight individuals: an adult pair, young of the year (kits), and yearlings from the previous litter. Lodges are usually 3 metres (10 feet) high and 6 metres (20 feet) across the base but can be as large as 5 metres (16 feet) high and 12 metres (39 feet) wide. One or more tunnel entrances open below the water’s surface and lead into a spacious central chamber above water level; the floor is covered with vegetation. An entry tunnel leads to the nest chamber above the waterline. In winter the moist walls freeze, adding insulation and making the lodge impenetrable to predators.

Beavers often construct a dam a short distance downstream from the lodge to deter predators. The dam impedes the flow of the stream and increases the depth of the water that surrounds the lodge. Dams also create additional wetland habitat for fish and waterfowl and contain or impede the downstream movement of oil spilled into rivers. Despite the environmental services these dams provide, land owners and farmers often regard beavers as nuisance animals because beavers sometimes destroy ornamental trees, devour crops, or flood roads and fields with water impounded behind their dams.

During winter beavers store some fat at the base of their tail, but they maintain body temperature primarily by huddling in the insulated lodge and being less active. They leave the lodge only to feed on branches cached beneath the ice. Slow swimmers, beavers can remain submerged for up to 15 minutes and propel themselves primarily with the webbed hind feet while the front feet are held tight against the body. On land they walk or run with a waddling gait. Their diet consists of the soft cambium layer beneath bark, as well as the buds, leaves, and twigs of certain trees (willows and aspens are preferred). Pond vegetation and bankside plants are also eaten. Herbaceous vegetation is consumed mostly during summer and woody matter during winter. Shrubs, saplings, and trees are felled by beavers, cut into portable lengths, and dragged along mud slides or floated through beaver-made canals to the lodge. Edible branches are cached underwater and anchored in mud near the lodge entrance, where they are to be eaten all winter when the beavers cannot break through the ice to cut fresh branches.

Beavers are monogamous, mating between January and March in the north and November or December in the south. One litter per year of one to nine (usually four) kits is born in the spring after a gestation of 105 days. Beavers communicate by postures, vocalization, scent marking, and tail slapping. When alarmed on land, they retreat to water and warn others by slapping the surface of the water with their tails, producing a loud, startling noise. Eagles, large hawks, and most large mammalian carnivores prey on beavers.

American beavers (Castor canadensis) occur throughout forested parts of North America to northern Mexico, including the southwestern United States and northern Florida. Beavers were at the heart of the fur trade during colonial times and contributed significantly to the westward settlement and development of North America and Canada. As the animal was trapped out in the east, trappers moved progressively westward, and settlers followed. Nearly extirpated by 1900 through excessive trapping for their luxuriant coat, they have reclaimed, either by natural movement or human reintroduction, much of their former natural range, and regulated trapping continues, particularly in Canada. American beavers have been introduced into Finland, where they are flourishing; by the 21st century the geographic range of this population had expanded into the Russian republic of Karelia.

Eurasian beavers (Castor fiber) were once found throughout temperate and boreal forests of the region (including Britain) except for the Mediterranean area and Japan. By the early 20th century this range had contracted, and at the beginning of the 21st century indigenous populations survived only in the Elbe and Rhône river drainages, southern Norway, France, Mongolia, China, and parts of Russia, especially northwestern Siberia and the Altai region. Efforts to reestablish the Eurasian species began in Sweden in the early 1920s. Since that time, Eurasian beavers have been reintroduced throughout Europe, western Siberia, western China, Mongolia, the Kamchatka Peninsula, and near the Amur River in the Russian Far East.

Beavers make up the family Castoridae (suborder Sciuromorpha, order Rodentia). With no close living relatives (the mountain beaver belongs to a separate family), modern beavers are remnants of a rich evolutionary history of 24 extinct genera extending back to the Late Eocene Age of Asia and the Early Oligocene of Europe and North America. Most were terrestrial burrowers, such as Palaeocastor, which is known by fossils from Late Oligocene–Early Miocene sediments of western Nebraska and eastern Wyoming. They probably lived in upland grasslands in large colonies, excavated extensive burrow systems, and grazed on the surface, their entire lifestyle being much like that of modern prairie dogs. The largest rodent that ever lived in North America was the amphibious giant beaver (Castoroides) of the Pleistocene Epoch. Fossils indicate that it had a body length of two metres (six feet) and was about the size of a black bear.

Additional Information

Beavers are famously busy, and they turn their talents to reengineering the landscape as few other animals can. When sites are available, beavers burrow in the banks of rivers and lakes. But they also transform less suitable habitats by building dams. Felling and gnawing trees with their strong teeth and powerful jaws, they create massive log, branch, and mud structures to block streams and turn fields and forests into the large ponds that beavers love.

Beaver Lodges

Domelike beaver homes, called lodges, are also constructed of branches and mud. They are often strategically located in the middle of ponds and can only be reached by underwater entrances. These dwellings are home to extended families of monogamous parents, young kits, and the yearlings born the previous spring.

Beavers are among the largest of rodents. They are herbivores and prefer to eat leaves, bark, twigs, roots, and aquatic plants.

Aquatic Adaptations

These large rodents move with an ungainly waddle on land but are graceful in the water, where they use their large, webbed rear feet like swimming fins, and their paddle-shaped tails like rudders. These attributes allow beavers to swim at speeds of up to five miles an hour. They can remain underwater for 15 minutes without surfacing, and have a set of transparent eyelids that function much like goggles. Their fur is naturally oily and waterproof.

There are two species of beavers, which are found in the forests of North America, Europe, and Asia. These animals are active all winter, swimming and foraging in their ponds even when a layer of ice covers the surface.

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Beaver

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