Litter consists of waste products that have been disposed improperly, without consent, in an inappropriate location. Litter can also be used as a verb. To litter means to throw (often man-made) objects onto the ground and leave them as opposed to disposing of them properly.
Larger hazardous items such as tires, appliances, electronics and large industrial containers are often dumped in isolated locations, such as National Forests and other public land.
It is a human impact on the environment and is a serious environmental issue in many countries. Litter can exist in the environment for long periods of time before degrading and be transported large distances into the world's oceans. Litter can affect quality of life.
Cigarette butts are the most littered item in the world, with 4.5 trillion discarded annually. Cigarette butts can take up to five years to completely break down. Statistics in 2003 showed metal/aluminum drink cans as the least littered item.
Throughout human history, people have disposed of unwanted materials without fear of retribution, onto streets, roadsides, in small local dumps or often in remote locations. Prior to reforms within cities in the mid-to-late 19th century, sanitation was not a government priority. The growing piles of waste led to the spread of disease.
To address the growing amount of waste generated in the United States, the Solid Waste Disposal Act of 1965 was enacted. In 1976 the Federal government amended the Solid Waste Disposal Act, creating the Resource Conservation and Recovery Act (RCRA), which requires a “cradle to grave” approach to the proper handling of potentially hazardous materials. RCRA gives authority to the Environmental Protection Agency (EPA) to regulate and enforce proper hazardous waste disposal. Many countries now have laws that require that household hazardous waste be deposited in a special location rather than sent to landfills with regular refuse. Household hazardous waste includes paints and solvents, chemicals, light bulbs, fluorescent lights, spray cans, and yard products such as fertilizers, pesticides, herbicides and insecticides. Additionally, medical waste generated at home is considered a hazardous waste and must be disposed of properly.
In addition to intentional littering, almost half of litter on U.S. roadways is now a result of accidental or unintentional litter, usually debris that falls off of improperly secured trash, recycling collection vehicles and pickup trucks. Population levels, traffic density and proximity to waste disposal sites are factors known to correlate with higher litter rates. Government neglect, the inability of governments to remove litter in a timely manner, is also a reason why humans are tempted to litter.
Illegally dumped hazardous waste may be affected by the costs associated with dropping materials at designated sites; some facilities charge a fee for depositing hazardous material. Access to nearby facilities that accept hazardous waste may deter use. Additionally, ignorance of the laws that regulate the proper disposal of hazardous waste may have an impact on proper disposal.
According to a study by the Dutch organization VROM, 80 percent of the people claim that "everybody leaves a piece of paper, tin or something, on the street behind". Young people from 12 to 24 years cause more litter than the average (Dutch or Belgian) person. Eighteen percent of people who regularly cause litter were 50 years of age or older. However, a 2010 survey of littering in Maine, New Hampshire and Vermont in the United States, placed litterers aged 55 and over at less than five percent. The same observational study estimated the overall average of litterers to be 78 percent male. Nevertheless, automobile drivers and recreationalists, smokers and youth are specific target groups within many campaigns conducted to keep countries free of litter.][ In 1999, research by Keep America Beautiful found that 75% of Americans admitted to littering the last five years, yet 99% of the same individuals admitted they enjoyed a clean environment.
Negligent or lenient law enforcement contributes to littering behavior.][ Other causes are inconvenience, entitlement and economic conditions.][ A survey of dumping in Pennsylvania found that the largest number of illegal dumps were in townships without municipal trash hauling. The same report also cites unavailability of curbside trash and recycling service, shortage of enforcement, and habit as possible causes. The presence of litter invites more littering.
The two-stage process model of littering behavior describes the different ways in which people litter. The model was proposed by Chris Sibley and James Liu and differentiates between two types of littering: active and passive.
The theory has implications for understanding the different types of litter reduction interventions that will most effectively reduce littering in a given environment. The theory states that, all things being equal, passive littering will be more resistant to change because of two psychological processes: 1. diffusion of responsibility that increases as the latency between when an individual places litter in the environment and when they vacate the territory, and 2. forgetting, which is also more likely to occur at longer delays between when an individual places litter in the environment and when they vacate the territory.
Litter can remain either visible for extended periods of time before it eventually biodegrades, with some items made of condensed glass, styrofoam or plastic possibly remaining in the environment for over a million years.
About 18 percent of litter, usually traveling through stormwater systems, ends up in local streams, rivers, and waterways. Uncollected litter can accrete and flow into streams, local bays and estuaries. Litter in the ocean either washes up on beaches or collects in Ocean gyres such as the Great Pacific Garbage Patch. About 80 percent of marine debris comes from land-based sources.
Some litter that is collected can be recycled, however degraded litter cannot be recycled and eventually degrades to sludge, often toxic. The majority of litter that is collected goes to landfills.
Litter can harm humans and the environment in different ways.
Hazardous materials contained within litter and illegally dumped rubbish can leach into water sources, contaminate soil and pollute the air.
Tires are the most often dumped hazardous waste. In 2007 the United States generated 262 million scrap tires. Thirty-eight states have laws that ban whole tires being deposited in landfills. Many of these discarded tires end up illegally dumped on public lands. Tires can become a breeding ground for insect vectors which can transmit disease to humans. Mosquitoes, which breed in stagnant water, can transmit West Nile Virus and Malaria. Rodents nest in accumulated tires and can transmit diseases such as Hantavirus
When tires are burned they can smolder for long periods of time emitting hundreds of chemical and compounds that pollute the air causing respiratory illnesses. Additionally the residue left behind can harm the soil and leach into groundwater.
Visual pollution is a major effect of litter.
Open containers such as paper cups or beverage cans can hold rainwater, providing breeding locations for mosquitoes. In addition, a spark has the potential to hit a piece of litter like a paper bag which could start a fire.
Litter can be hazardous. Debris falling from vehicles is an increasing cause of automobile accidents. Over 800 Americans are killed each year in debris/litter-attributed motor vehicle collisions. Discarded dangerous goods, sharps waste and pathogens resulting from litter can cause accidental harm to humans.
Litter also carries substantial cost to the economy. Cleaning up litter in the U.S. costs hundreds of dollars per ton, about ten times more than the cost of trash disposal, for a cost totaling about $11 billion per year.
Animals may get trapped or poisoned with litter in their habitats. Cigarette butts and filters are a threat to wildlife and have been found in the stomachs of fish, birds and whales, who have mistaken them for food. Also animals can get trapped in the rubbish and be in serious discomfort. For example, the plastic used to hold beverage cans together can get wrapped around animals' necks and cause them to suffocate as they grow. Other instances where animals could be harmed by litter include broken glass lacerating the paws of dogs, cats, and other small mammals, fishing net being caught around the neck of a seal, etc.
Organic litter in large amounts can cause water pollution and lead to algal blooms. Cigarettes could also start fires if they are not put out and then discarded in the environment.
Litter is an environmental issue in many countries around the world. While countries in the developing world lack the resources to deal with the issue, consumer based economies in the western world are capable of generating larger quantities of litter per capita due to a higher consumption of disposable products.
Public waste containers or street bins are provided by local authorities to be used as a convenient place for the disposal and collection of litter. Increasingly both general waste and recycling options are provided. Local councils pick the waste up and take it to refuse or recycling. However there are issues with this approach. If the bins are not regularly emptied, then overfilling of bins occurs and can increase litter indirectly. Some local authorities will only take responsibility for rubbish that is placed in the bins, which means that litter remains a problem. People may blame a lack of well-placed bins for their littering. Hazardous materials may be incorrectly disposed of in the bins and they can encourage dumpster diving.
Volunteers, sometimes alone or coordinated through organisations will pick up litter and dispose of it. Clean up events may be organised where participants will sometimes comb an area in a line to ensure that no litter is missed. In North America, Adopt a Highway programs are popular, where companies and organizations commit to cleaning stretches of road. Increasingly, geocaching is used (see Cache In Trash Out). In Kiwayu, a Kenyan island, some of the collected litter (flip-flops) is used for making art, which is then sold (see FlipFlop Recycling Company).
Picking up litter can be hazardous. Hazards can include exposure to dangerous goods, sharps waste and pathogens. As a result, safety equipment is sometimes worn and tools such as litter grabbers (extendable arms) are used.
Container deposit legislation can be aimed at both reducing littering and also encouraging picking up through local recycling programs that offer incentives, particularly for aluminium cans, glass bottles and plastic bottles. In New York, an expanded bottle bill that included plastic water bottles increased recycling rates and generated 120 million dollars in revenue to the state General Fund from unclaimed deposits in 2010.
Litter traps can be used to capture litter as it exits stormwater drains into waterways. However, litter traps are only effective for large or floating items of litter and must be maintained.
Increasingly, there have been efforts to use technology to monitor areas prone to dumping. In Japan, a study used Geographic Information Systems (GIS) to map areas of dumping based on site characteristics.
Some countries and local authorities have introduced legislation to address the problem.
Actions resulting in fines can include on-the-spot fines for individuals administered by authorised officers in public or on public transport or littering from a vehicle, in which the vehicle owner is fined - reported by either responsible officer or third party, sometimes online.
Specific legislation exists in the following countries:
A number of organisations exist with the aim of raising awareness and run campaigns including clean up events. Clean Up the World is a worldwide campaign.
In the United States there are a number of organisations running anti-litter campaigns. Keep America Beautiful was founded in 1953. At least 38 states have high profile, government-recognized slogan campaigns, including Don't Mess with Texas; Let's Pick It Up New York; Don't Trash California; Take Pride in Florida; Keep Iowa Beautiful.
In Australia, Clean Up Australia Day is supported by many major Australian companies, firms and volunteers alike. Anti-litter organisations include Keep Australia Beautiful founded in 1963 that created the popular “Do the Right Thing” campaign and its Tidy Towns competition became well known being a very competitive expression of civic pride.
Keep Britain Tidy is a British campaign run by the Keep Britain Tidy environmental charity, which is part funded by the U.K. government.
C. fiber – Eurasian beaver
C. canadensis – North American beaver
The beaver (genus Castor) is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American beaver (Castor canadensis) (native to North America) and Eurasian beaver (Castor fiber) (Eurasia). 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 due to extensive hunting for fur, for glands used as medicine and perfume, and because their harvesting of trees and flooding of waterways may interfere with other land uses.
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. 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 are herbivores, and prefer the wood of quaking aspen, cottonwood, willow, alder, birch, maple and cherry trees. They also eat sedges, pondweed, and water lilies.
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.
Fossil remains of beavers are found in the peat and other superficial deposits of Britain and the continent of Europe; while in the Pleistocene formations of Britain and Siberia, remains of a giant extinct beaver have been found, Trogontherium cuvieri, representing a genus by itself.
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 that they will not be worn down by chewing on wood. 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.
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.
The word beaver (plural beaver or beavers) is descended from the Proto-Indo-European name of the animal, cf. Sanskrit babhru's, brown, Lat. fiber, Ger. Biber, Russ. bobr; the root bhru has given "brown", and, through Romanic, "bronze" and "burnish". It is probable that beaver in English is either borrowed from the Old French bièvre or both came directly from the Celtic *befros. Castor supplanted bièvre in the course of the twelfth century in France.
They are the only extant members of the family Castoridae, which contains a single genus, Castor. Genetic research has shown the European and North American beaver populations to be distinct species and that hybridization is unlikely. Beavers are closely related to squirrels (Sciuridae), agreeing in certain structural peculiarities of the lower jaw and skull. In the Sciuridae the two main bones (tibia and fibula) of the lower half of the leg are quite separate, the tail is round and hairy, and the habitats are arboreal and terrestrial. In the beavers or Castoridae these bones are in close contact at their lower ends, the tail is depressed, expanded and scaly, and their habitats are aquatic.
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 breed. Finally, 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.
The two species are not genetically compatible. North American beavers have 40 chromosomes, while Eurasian 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.
The Eurasian beaver (Castor fiber) was nearly hunted to extinction in Europe, both for fur and for castoreum, a secretion of its scent gland believed to have medicinal properties. However, the beaver is now being re-introduced throughout Europe. Several thousand live on the Elbe, the Rhone 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), 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, and 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.
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 parts of northern Mexico. The chief feature distinguishing C. canadensis from C. fiber is the form of the nasal bones of the skull. This species was introduced to the Argentine and Chilean Tierra del Fuego, as well as Finland, France, Poland and Russia.
The North American beaver's preferred food is the water-lily (genus Nuphar), which bears a resemblance to a cabbage-stalk, and grows at the bottom of lakes and rivers. Beavers also gnaw the bark of birch, poplar, and willow trees; but during the summer a more varied herbage, with the addition of berries, is consumed. These animals are often trapped for their fur. During the early 19th century, trapping eliminated this animal from large portions of its original range. However, through trap and transfer and habitat conservation it made a nearly complete recovery by the 1940s. 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. Native peoples and early settlers also ate this animal's meat. The current beaver population has been estimated to be 10 to 15 million; one estimate claims that there may at one time have been as many as 90 million.
The habitat of the beaver is the riparian zone, inclusive of stream bed. The actions of beavers for hundreds of thousands of years][ in the Northern Hemisphere have kept these watery systems healthy and in good repair, although a human observing all the downed trees might think that the beavers were doing just the opposite.
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. Beavers potentially even impact climate change.
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.][
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.)
The ponds created by well-maintained dams help isolate the beavers' homes, their lodges, which are created from severed branches and mud. The beavers cover their lodges late every autumn with fresh mud, which freezes when the frost sets in. The mud becomes almost as hard as stone, and neither wolves nor wolverines can penetrate it.
The lodge has underwater entrances to make entry nearly impossible for any other animal (however, muskrats have been seen living inside beaver lodges with the beavers who made them). A very small amount of the lodge is actually used as a living area. Contrary to popular belief, beavers actually 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 where the family actually lives.
Beaver houses are formed of the same materials as the dams, with little order or regularity of structure, and seldom contain more than four adult and six or eight young beavers. Some of the larger houses have one or more partitions, but these are only posts of the main building left by the builders to support the roof, for the apartments usually have no communication with each other except by water.
When the ice breaks up in spring beavers always leave their embankments and rove about until just before fall, when they return to their old habitations and lay in their winter stock of wood. They seldom begin to repair the houses until the frost sets in, and never finish the outer coating until the cold becomes severe. When they erect a new habitation they fell the wood early in summer, but seldom begin building until nearly the end of August.
Beaver lodge, approx. 20-foot (6.1 m) diameter. Ontario, Canada
Illustration of lodge
Beaver ponds, and the wetlands that succeed them, remove sediments and pollutants from waterways, including total suspended solids, total nitrogen, phosphates, carbon and silicates.
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 by other humans. Norway has many beaver 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. 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.
After 200 years, a beaver has returned to New York City, making its home along the Bronx River, having spent time living at the Bronx Zoo as well as the Botanical Gardens. Beavers were trapped to near extirpation and had not been seen in New York City since the early 1800s. The return of "Jose", named after Representative Jose Serrano from the Bronx, is seen as evidence that efforts to restore the river have been successful. "Jose Serrano" has been sighted below the East Tremont bridge at Drew Gardens as recently as June 2009.
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. Relocation costs $4,000–$4,500 per animal. Scott Garrow, District Wildlife Biologist with the Illinois Department of Natural Resources, opined that relocating the beavers may be "a waste of time", as there are records of beaver recolonizing North Pond in Lincoln Park in 1994, 2003, 2004, 2008 and 2009. As of fall 2009 a new beaver lodge has appeared on North Pond's northwest bank.
Outside San Francisco, in downtown Martinez, California, a male and female beaver arrived in Alhambra Creek in 2006. The Martinez beavers built a dam 30 feet wide and at one time 6 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". Resolution included installing a pipe through the beaver dam so that the pond's water level could not become excessive. Now protected, the beaver have transformed Alhambra Creek from a trickle into multiple dams and beaver ponds, which in turn, led to the return of steelhead trout and North American river otter in 2008, and mink in 2009. The Martinez beavers probably originated from the Sacramento-San Joaquin River Delta which once held the largest concentration of beaver in North America.
In Aurora, Colorado, at the Star-K Ranch Park, two active beaver dams and one inactive beaver dam may be seen, with a beaver burrow in the north banks of the Sand Creek along the active beaver pond.
Beaver lodge re-appears in Chicago's North Pond, December 2009|right
Mink returns to Beaver Pond near San Francisco, 2009
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. 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.][ They have also been found to cross saltwater 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 impacts on native stream fishes in the Cape Horn Biosphere Reserve, Chile.
Beavers are classed as a "prohibited new organism" under New Zealand's Hazardous Substances and New Organisms Act 1996, preventing it from being imported into the country.
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. 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. 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. 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. 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. 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.
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. 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 only stay and help their families if there is a shortage of resources in times of food shortage, high population density, or drought. When beavers leave their natal territories, they usually do not settle far. Beavers can recognize their kin by detecting differences in anal gland secretion composition using their keen sense of smell. Related beavers share more features in their anal gland secretion profile than unrelated beavers. Being able to recognize kin is important for beaver social behavior and it causes more tolerant behavior among neighboring beavers.
Beavers maintain and defend territories, which are areas for feeding, nesting and mating. They invest much energy in their territories, building their dams and becoming familiar with the area. Beavers mark their territories by constructing scent mounts made of mud, debris and castoreum, a urine based substance excreted through the beavers castor sacs between the pelvis and base of the tail. These scent mounts are established on the border of the territory. Once a beaver detects another scent in its territory, finding the intruder takes priority, even over food. 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. 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. Scent marking increases in August during the dispersal of yearlings, in an attempt to prevent them from intruding on territories. 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. As such they respond less aggressively to intrusions by their territorial neighbours than those made by non-territorial floaters or "strangers".
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.
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 (Eskimo) medicine used dried beaver testicles like willow bark to relieve pain. Dried beaver testicles were also used as contraception. Beaver testicles were used as medicine in Iraq and Iran during the tenth to nineteenth century. Claudius Aelianus comically described beavers chewing off their testicles to preserve themselves from hunters, which is not possible because the beaver's testicles are inside its body. 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. Castoreum continues to be used in perfume production.
Much of the early European exploration and trade of Canada was based on the quest for beaver. The most valuable part of the 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 an Indian had worn or slept on was more valuable than a fresh skin since this tended to wear off the outer guard hairs.
Beavers have been trapped for millennia, and this continues to this day. 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.
In wider culture, the beaver is famed for its industriousness. The English verb "to beaver" means to work hard and constantly.
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. 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 RégimenteRoyal 22 and the Canadian Military Engineers. Toronto Police Services, London Police Service, Canadian Pacific Railway Police Service and Canadian Pacific Railway crest bears the beaver on their crest or coat of arms.
Others who have used the beaver in their company or organizational symbol or as their mascot include:
In the 17th century, based on a question raised by the Bishop of Quebec, the Roman Catholic Church ruled that the beaver was a fish (beaver flesh was a part of the indigenous peoples' diet, prior to the Europeans' arrival) for purposes of dietary law. Therefore, the general prohibition on the consumption of meat on Fridays during Lent did not apply to beaver meat. 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. This is similar to the Church's classification of the capybara, another semi-aquatic rodent.
In computability theory, a busy beaver (from the colloquial expression for "industrious person") is a Turing machine that attains the maximum "operational busyness" (such as measured by the number of steps performed, or the number of nonblank symbols finally on the tape) among all the Turing machines in a certain class.
Weaning is the process of gradually introducing a mammal infant to what will be its adult diet and withdrawing the supply of its mother's milk.
The process takes place only in mammals, as only mammals produce milk. The infant is considered to be fully weaned once it no longer receives any breast milk (or bottled substitute).
How and when to wean a human infant is a subject of much controversy. The American Academy of Pediatrics recommends feeding a baby only breast milk for the first 6 months of its life, and continuing breastfeeding until the child is at least one year old and for as long after that as the mother and child both wish to continue. However many mothers find breastfeeding challenging, especially in modern times when many mothers have to return to work relatively soon after the birth of their child.
The American Academy of Pediatrics and the World Health Organization recommend waiting until 6 months to introduce baby food. However, many baby food companies market their "stage 1" foods to children between 4 and 6 months old with the precaution that the food is meant to be consumed in addition to breast milk or formula and is just for "practice". These practice foods are generally soft and runny. Examples include mashed fruit and vegetables. Certain foods are recommended to be avoided. The United Kingdom's NHS recommends withholding foods including those "that contain wheat, gluten, nuts, peanuts, peanut products, seeds, liver, eggs, fish, shellfish, cows’ milk and soft or unpasteurised cheese" until a baby is six months old, as they may cause food allergies or make the baby ill. However, recommendations such as these have been called into question by research that suggests early exposure to potential allergens does not increase the likelihood of allergies.
In many cultures around the world, weaning progresses with the introduction of feeding the child food that has been prechewed by the parent along with continued breastfeed, a practice known as premastication. The practice was important in human history in that it naturally gave a child a greatly improved protein source and also that prevents infant iron deficiency. The prechewing of food also allows gives thet baby long-term immunological benefits through factors in the mother's saliva. However, premasticated food from caregivers of lower socioeconomic status in areas of endemic diseases can result in passing the disease to the child.
No matter what age baby food is introduced, it is generally a very messy affair, as young children do not have the coordination to eat "neatly".][ Coordination for using utensils properly and eating with dexterity takes years to develop. Many babies begin using utensils between 10 and 14 months, but most will not be able to feed themselves well until about 2 or 3 years of age.][
At this point, the mother tries to force the infant to cease nursing, while the infant attempts to force the mother to continue. From an evolutionary perspective, weaning conflict may be considered the result of the cost of continued nursing to the mother, perhaps in terms of reduced ability to raise future offspring, exceeding the benefits to the mother in terms of increased survival of the current infant. This can come about because future offspring will be equally related to the mother as the current infant, but will share less than 100% of the current infant's genes. So, from the perspective of the mother's evolutionary fitness, it makes sense for her to cease nursing the current infant as soon as the cost to future offspring exceeds the benefit to the current infant. But, assuming the current infant shares 50% of the future offsprings' genes, from the perspective of the infant's own evolutionary fitness, it makes sense for the infant to continue nursing until the cost to future offspring exceeds twice the benefit to itself (perhaps less, depending on the number of potential future offspring). Weaning conflict has been studied for a variety of mammal species, including primates and canines.
There is significant individual and cultural variation in time of weaning.
Scientifically, one can ask various questions; some of the most straightforwardly empirical include:
As there are significant ranges and skew in these numbers (some infants are never nursed, or only nursed briefly, for instance), looking at the median (half-way mark) is more useful than looking at the average.
Considering biological measures of maturity, notably investigated by Kathy Dettwyler, yields a range of ages from 2 1/2 years to 7 years as the weaning age analogous to other primates – the "natural age of weaning". This depends on the measure, for example: weaning in non-human primates is often associated with eruption of permanent molars (humans: 5 1/2 to 6 years); comparing duration of nursing to length of pregnancy (gestation time) yields a factor of about 6 in chimpanzees and gorillas (humans: 6×9 months = 54 months = 4 1/2 years); body weight may be compared to birth weight (quadrupling of birth weight yields about 2 1/2 to 3 1/2 years for humans; 1/3 of adult weight yields 5 to 7 years for humans); and similarly for other measures.
The age at which children are normatively weaned can vary significantly between cultures, "from 6 months to 5 1/2 years".][ There is often a cultural expectation in the United States that children be weaned early.][
Other studies are possible, as in psychological factors. For example, Barbara Rogoff has noted, citing a 1953 study by Whiting & Child, that the most distressing time to wean a child is at 13–18 months. After this peak, weaning becomes progressively easier and less distressing for the child, with "older children frequently wean[ing] themselves."
In science, mice are frequently used in laboratory experiments. When breeding laboratory mice in a controlled environment, the weaning is defined as the moment when the pups are transferred out of the mothers' cage. Weaning is recommended at 3 to 4 weeks after parturition.
For pet carnivores such as dogs or cats, there are special puppy or kitten foods commercially available. Alternatively, if the pet owner feeds the parent animals home-made pet food, the young can be fed the same foods chopped into small pieces.