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123-562: The brown rat ( Rattus norvegicus ), also known as the common rat , street rat , sewer rat , wharf rat , Hanover rat , Norway rat and Norwegian rat , is a widespread species of common rat . One of the largest muroids , it is a brown or grey rodent with a body length of up to 28 cm (11 in) long, and a tail slightly shorter than that. It weighs between 140 and 500 g (4.9 and 17.6 oz). Thought to have originated in northern China and neighbouring areas, this rodent has now spread to all continents except Antarctica , and

246-457: A mischief . The common species are opportunistic survivors and often live with and near humans ; therefore, they are known as commensals . They may cause substantial food losses, especially in developing countries. However, the widely distributed and problematic commensal species of rats are a minority in this diverse genus. Many species of rats are island endemics , some of which have become endangered due to habitat loss or competition with

369-582: A clinical setting, this management is offered by otologists and audiologists . Hearing loss is associated with Alzheimer's disease and dementia with a greater degree of hearing loss tied to a higher risk. There is also an association between type 2 diabetes and hearing loss . Hearing threshold and the ability to localize sound sources are reduced underwater in humans, but not in aquatic animals, including whales, seals, and fish which have ears adapted to process water-borne sound. Not all sounds are normally audible to all animals. Each species has

492-509: A deterrent simply by their presence. Rats have the ability to swim up sewer pipes into toilets. Rats will infest any area that provides shelter and easy access to sources of food and water, including under sinks, near garbage, and inside walls or cabinets. Rats can serve as zoonotic vectors for certain pathogens and thus spread disease, such as bubonic plague , Lassa fever , leptospirosis , and Hantavirus infection. Researchers studying New York City wastewater have also cited rats as

615-402: A distinct "chirping", has been likened to laughter , and is interpreted as an expectation of something rewarding. Like most rat vocalizations, the chirping is too high in pitch for humans to hear without special equipment. Bat detectors are often used by pet owners for this purpose. In research studies, the chirping is associated with positive emotional feelings, and social bonding occurs with

738-617: A dozen diseases directly linked to rats. Most urban areas battle rat infestations. A 2015 study by the American Housing Survey (AHS) found that eighteen percent of homes in Philadelphia showed evidence of rodents. Boston , New York City , and Washington, D.C. , also demonstrated significant rodent infestations. Indeed, rats in New York City are famous for their size and prevalence. The urban legend that

861-497: A measure as employing an anechoic chamber , which absorbs nearly all sound. Another means is the use of devices such as earplugs , which are inserted into the ear canal to block noise, or earmuffs , objects designed to cover a person's ears entirely. The loss of hearing, when it is caused by neural loss, cannot presently be cured. Instead, its effects can be mitigated by the use of audioprosthetic devices, i.e. hearing assistive devices such as hearing aids and cochlear implants . In

984-464: A mental ability previously only found in humans and some other primates, but further analysis suggested they may have been following simple operant conditioning principles. Brown rats are capable of producing ultrasonic vocalizations. As pups, young rats use different types of ultrasonic cries to elicit and direct maternal search behavior, as well as to regulate their mother's movements in the nest. Although pups produce ultrasounds around any other rats at

1107-534: A minimum. The effectiveness has been aided by a similar but newer program in Saskatchewan which prevents rats from even reaching the Alberta border. Alberta still employs an armed rat patrol to control rats along Alberta's borders. About ten single rats are found and killed per year, and occasionally a large localized infestation has to be dug out with heavy machinery, but the number of permanent rat infestations

1230-667: A modern myth, the rat flood in India occurs every fifty years, as armies of bamboo rats descend upon rural areas and devour everything in their path. Rats have long been held up as the chief villain in the spread of the Bubonic Plague ; however, recent studies show that rats alone could not account for the rapid spread of the disease through Europe in the Middle Ages . Still, the Centers for Disease Control does list nearly

1353-445: A new area, they quickly reproduce to take advantage of the new food supply. In particular, they prey on the eggs and young of forest birds, which on isolated islands often have no other predators and thus have no fear of predators . Some experts believe that rats are to blame for between forty percent and sixty percent of all seabird and reptile extinctions, with ninety percent of those occurring on islands. Thus man has indirectly caused

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1476-581: A number of pathogens, which can result in disease, including Weil's disease , rat bite fever , cryptosporidiosis , viral hemorrhagic fever , Q fever and hantavirus pulmonary syndrome . In the United Kingdom, brown rats are an important reservoir for Coxiella burnetii , the bacterium that causes Q fever, with seroprevalence for the bacteria found to be as high as 53% in some wild populations. Rat Rats are various medium-sized, long-tailed rodents . Species of rats are found throughout

1599-603: A popular choice due to their high intelligence, ingenuity, aggressiveness , and adaptability . Their psychology seems in many ways similar to that of humans. Inspired by B.F. Skinner ’s famous box which dispensed food pellets when rats pushed a lever, photographer Augustin Lignier gave two rats periodic, unpredictable rewards for pressing a button. He likened their repeated button-pressing behaviors to people’s fascinations with digital and social media. Early studies found evidence both for and against measurable intelligence using

1722-462: A province in 1905. Black rats cannot survive in its climate at all, and brown rats must live near people and in their structures to survive the winters. There are numerous predators in Canada's vast natural areas which will eat non-native rats, so it took until 1950 for invading rats to make their way over land from Eastern Canada. Immediately upon their arrival at the eastern border with Saskatchewan ,

1845-556: A quick temper and wastefulness. People born in a year of the rat are said to get along well with "monkeys" and "dragons", and to get along poorly with "horses". In Indian tradition, rats are seen as the vehicle of Ganesha , and a rat's statue is always found in a temple of Ganesh. In the northwestern Indian city of Deshnoke , the rats at the Karni Mata Temple are held to be destined for reincarnation as Sadhus ( Hindu holy men). The attending priests feed milk and grain to

1968-438: A range of normal hearing for both amplitude and frequency . Many animals use sound to communicate with each other, and hearing in these species is particularly important for survival and reproduction. In species that use sound as a primary means of communication, hearing is typically most acute for the range of pitches produced in calls and speech. Frequencies capable of being heard by humans are called audio or sonic. The range

2091-473: A serious threat to many of New Zealand's native wildlife . Rat eradication programmes within New Zealand have led to rat-free zones on offshore islands and even on fenced "ecological islands" on the mainland. Before an eradication effort was launched in 2001, the sub-Antarctic Campbell Island had the highest population density of brown rats in the world. Similar to other rodents , brown rats may carry

2214-415: A space next to their closest friend, also explained in the name; allo-grooming, so-called to distinguish it from self-grooming; and nosing, where a rat gently pushes with its nose at another rat near the neck. Rats are known to burrow extensively, both in the wild and in captivity, if given access to a suitable substrate . Rats generally begin a new burrow adjacent to an object or structure, as this provides

2337-410: A state of proprioceptive balance in its environment. Further mechanobiological investigations of the constituent tendons in the tail of the rat have identified multiple factors that influence how the organism navigates its environment with this structure. A particular example is that of a study in which the morphology of these tendons is explicated in detail. Namely, cell viability tests of tendons of

2460-441: A sturdy "roof" for the section of the burrow nearest to the ground's surface. Burrows usually develop to eventually include multiple levels of tunnels, as well as a secondary entrance. Older male rats will generally not burrow, while young males and females will burrow vigorously. Burrows provide rats with shelter and food storage, as well as safe, thermo-regulated nest sites. Rats use their burrows to escape from perceived threats in

2583-653: A successful trial on the smaller Hawea Island nearby. In January 2015, an international "Rat Team" set sail from the Falkland Islands for the British Overseas Territory of South Georgia and the South Sandwich Islands on board a ship carrying three helicopters and 100 tons of rat poison with the objective of "reclaiming the island for its seabirds". Rats have wiped out more than 90% of the seabirds on South Georgia, and

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2706-656: A terrible scattering of light within its vision. Brown rats are dichromats which perceive colors rather like a human with red-green colorblindness , and their colour saturation may be quite faint. Their blue perception, however, also has UV receptors, allowing them to see ultraviolet lights that humans and some other species cannot. The brown rat is nocturnal and is a good swimmer, both on the surface and underwater, and has been observed climbing slim round metal poles several feet in order to reach garden bird feeders. Brown rats dig well, and often excavate extensive burrow systems. A 2007 study found brown rats to possess metacognition ,

2829-415: A thermoregulation function that follows from its anatomical construction. This particular tail morphology is evident across the family Muridae, in contrast to the bushier tails of Sciuridae , the squirrel family. The tail is hairless and thin skinned but highly vascularized, thus allowing for efficient countercurrent heat exchange with the environment. The high muscular and connective tissue densities of

2952-428: A unique defense mechanism known as degloving in which the outer layer of the integument can be detached in order to facilitate the animal's escape from a predator. This evolutionary selective pressure has persisted despite a multitude of pathologies that can manifest upon shedding part of the tail and exposing more interior elements to the environment. Paramount among these are bacterial and viral infection, as

3075-456: A visit to the vet. The noise is best described as either a quick clicking or 'burring' sound, varying from animal to animal. Vigorous bruxing can be accompanied by boggling, where the eyes of the rat rapidly bulge and retract due to movement of the lower jaw muscles behind the eye socket. In addition, they commonly squeak along a range of tones from high, abrupt pain squeaks to soft, persistent 'singing' sounds during confrontations. The brown rat

3198-590: A year. In 1769, they were observed in Tórshavn on the southern part of Streymoy , and a decade later, in the villages in the northern part of this island. From here, they crossed the strait and occupied Eysturoy during the years 1776 to 1779. In 1779, they reached Vagar . Whether the rats dispersed from the already established population in Suðuroy, or they were brought to the Faroe Islands with other ships

3321-434: Is tonotopic , so that each frequency has a characteristic place of resonance along it. Characteristic frequencies are high at the basal entrance to the cochlea, and low at the apex. Basilar membrane motion causes depolarization of the hair cells , specialized auditory receptors located within the organ of Corti. While the hair cells do not produce action potentials themselves, they release neurotransmitter at synapses with

3444-472: Is 822 g (29 oz) and they can reach a maximum length of 48.5 cm (19 in). Brown rats have acute hearing , are sensitive to ultrasound , and possess a very highly developed olfactory sense . Their average heart rate is 300 to 400 beats per minute, with a respiratory rate of around 100 per minute. The vision of a pigmented rat is poor, around 20/600, while a non-pigmented (albino) with no melanin in its eyes has both around 20/1200 vision and

3567-481: Is a major agricultural area, Alberta is far from any seaport and only a portion of its eastern boundary with Saskatchewan provides a favorable entry route for rats. Brown rats cannot survive in the wild boreal forest to the north, the Rocky Mountains to the west, nor can they safely cross the semiarid High Plains of Montana to the south. The first brown rat did not reach Alberta until 1950, and in 1951,

3690-507: Is a true omnivore and consumes almost anything, but cereals form a substantial part of its diet. The most-liked foods of brown rats include scrambled eggs , raw carrots, and cooked corn kernels. The least-liked foods are raw beets, peaches and raw celery. Foraging behavior is often population-specific, and varies by environment and food source. Brown rats living near a hatchery in West Virginia catch fingerling fish. Some colonies along

3813-479: Is an additional important part of rat socialization. Huddling, an extreme form of herding and like chattering or "bruxing" is often used to communicate that they are feeling threatened and not to come near. The common rat has been more successful at inhabiting and building communities on 6 continents and are the only species to have occupied more land than humans. During the wintry months, rats will huddle into piles – usually cheek-to-cheek – to control humidity and keep

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3936-405: Is an airtight membrane, and when sound waves arrive there, they cause it to vibrate following the waveform of the sound. Cerumen (ear wax) is produced by ceruminous and sebaceous glands in the skin of the human ear canal, protecting the ear canal and tympanic membrane from physical damage and microbial invasion. The middle ear consists of a small air-filled chamber that is located medial to

4059-609: Is estimated that brown rat populations will see an increase. In tropical and desert regions, brown rat occurrence tends to be limited to human-modified habitats. Contiguous rat-free areas in the world include the continent of Antarctica, the Arctic , some isolated islands, the Canadian province of Alberta , and certain conservation areas in New Zealand. Most of Australia apart from the eastern and south-eastern coastal areas does not have reports of substantial rat occurrences. Antarctica

4182-409: Is estimated, with predators and interspecies conflict as major causes. When lactating, female rats display a 24-hour rhythm of maternal behavior, and will usually spend more time attending to smaller litters than large ones. Brown rats live in large, hierarchical groups, either in burrows or subsurface places, such as sewers and cellars. When food is in short supply, the rats lower in social order are

4305-469: Is lower. It is difficult to determine the extent of their home range because they do not utilize a whole area but rather use regular runways to get from one location to another. There is great debate over the size of the population of rats in New York City , with estimates from almost 100 million rats to as few as 250,000. Experts suggest that New York is a particularly attractive place for rats because of its aging infrastructure and high poverty rates. In 2023,

4428-470: Is much safer to use near humans and other large animals than arsenic. By 1960, the number of rat infestations in Alberta had dropped to below 200 per year. In 2002, the province finally recorded its first year with zero rat infestations, and from 2002 to 2007 there were only two infestations found. After an infestation of rats in the Medicine Hat landfill was found in 2012, the province's rat-free status

4551-462: Is not directly coupled with frequency range. Georg Von Békésy in 1929 identifying sound source directions suggested humans can resolve timing differences of 10μs or less. In 1976 Jan Nordmark's research indicated inter-aural resolution better than 2μs. Milind Kuncher's 2007 research resolved time misalignment to under 10μs. Even though they do not have ears, invertebrates have developed other structures and systems to decode vibrations traveling through

4674-466: Is notable for being the largest inhabited area on Earth which is free of true rats due to very aggressive government rat control policies. It has large numbers of native pack rats , also called bushy-tailed wood rats, but they are forest-dwelling vegetarians which are much less destructive than true rats. Alberta was settled by Europeans relatively late in North American history and only became

4797-479: Is punishable by a penalty of up to C$ 5,000 or up to 60 days in jail. The adjacent and similarly landlocked province of Saskatchewan initiated a rat control program in 1972, and has managed to reduce the number of rats in the province substantially, although they have not been eliminated. The Saskatchewan rat control program has considerably reduced the number of rats trying to enter Alberta. First arriving before 1800 (perhaps on James Cook's vessels), brown rats pose

4920-647: Is restricted, she can extend pregnancy by over two weeks, and give birth to litters of normal number and weight. Males can ejaculate multiple times in a row, and this increases the likelihood of pregnancy as well as decreases the number of stillborns. Multiple ejaculation also means that males can mate with multiple females, and they exhibit more ejaculatory series when there are several oestrous females present. Males also copulate at shorter intervals than females. In group mating, females often switch partners. Dominant males have higher mating success and also provide females with more ejaculate, and females are more likely to use

5043-424: Is subject to special measures and regularly monitored for rat invasions. As part of island restoration , some islands' rat populations have been eradicated to protect or restore the ecology . Hawadax Island, Alaska was declared rat free after 229 years and Campbell Island, New Zealand after almost 200 years. Breaksea Island in New Zealand was declared rat free in 1988 after an eradication campaign based on

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5166-687: Is the dominant rat in Europe and much of North America. With rare exceptions, the brown rat lives wherever humans live, particularly in urban areas. Selective breeding of the brown rat has produced the fancy rat (rats kept as pets), as well as the laboratory rat (rats used as model organisms in biological research). Both fancy rats and laboratory rats are of the domesticated subspecies Rattus norvegicus domestica . Studies of wild rats in New York City have shown that populations living in different neighborhoods can evolve distinct genomic profiles over time, by slowly accruing different traits. The brown rat

5289-416: Is the largest rat-free populated area in the world. Rat invasions of Alberta were stopped and rats were eliminated by very aggressive government rat control measures, starting during the 1950s. The only Rattus species that is capable of surviving the climate of Alberta is the brown rat, which can only survive in the prairie region of the province, and even then must overwinter in buildings. Although it

5412-430: Is the use of devices designed to prevent noise-induced hearing loss (NIHL), a type of post-lingual hearing impairment . The various means used to prevent hearing loss generally focus on reducing the levels of noise to which people are exposed. One way this is done is through environmental modifications such as acoustic quieting , which may be achieved with as basic a measure as lining a room with curtains , or as complex

5535-494: Is typically considered to be between 20 Hz and 20,000 Hz. Frequencies higher than audio are referred to as ultrasonic , while frequencies below audio are referred to as infrasonic . Some bats use ultrasound for echolocation while in flight. Dogs are able to hear ultrasound, which is the principle of 'silent' dog whistles . Snakes sense infrasound through their jaws, and baleen whales , giraffes , dolphins and elephants use it for communication. Some fish have

5658-501: Is uninhabitable by rats. The Arctic has extremely cold winters that rats cannot survive outdoors, and the human population density is extremely low, making it difficult for rats to travel from one habitation to another, although they have arrived in many coastal areas by ship. When the occasional rat infestation is found and eliminated, the rats are unable to re-infest it from an adjacent one. Isolated islands are also able to eliminate rat populations because of low human population density and

5781-412: Is unknown. The Northern islands were invaded by the brown rat more than 100 years later, after Norwegians built and operated a whaling station in the village of Hvannasund on Borðoy from 1898 to 1920. From there, the brown rat spread to the neighbouring islands of Viðoy and Kunoy . A recent genomic analysis reveals three independent introductions of the invasive brown rat to the Faroe Islands. Today

5904-421: Is usually brown or dark grey, while the underparts are lighter grey or brown. The brown rat is a rather large murid and can weigh twice as much as a black rat ( Rattus rattus ) and many times more than a house mouse ( Mus musculus ). The head and body length ranges from 15 to 28 cm (5.9 to 11.0 in) while the tail ranges in length from 10.5 to 24 cm (4.1 to 9.4 in), therefore being shorter than

6027-621: Is zero. Ancient Romans did not generally differentiate between rats and mice, instead referring to the former as mus maximus (big mouse) and the latter as mus minimus (little mouse). On the Isle of Man , there is a taboo against the word " rat ". The rat (sometimes referred to as a mouse) is the first of the twelve animals of the Chinese zodiac . People born in this year are expected to possess qualities associated with rats, including creativity, intelligence, honesty, generosity, ambition,

6150-510: The "g factor" in rats. Part of the difficulty of understanding animal cognition , generally, is determining what to measure. One aspect of intelligence is the ability to learn, which can be measured using a maze like the T-maze . Experiments done in the 1920s showed that some rats performed better than others in maze tests, and if these rats were selectively bred, their offspring also performed better, suggesting that in rats an ability to learn

6273-566: The aortic branches . Aortic arches studied in rats exhibit abnormalities similar to those of humans, including altered pulmonary arteries and double or absent aortic arches. Despite existing anatomical analogy in the inthrathoracic position of the heart itself, the murine model of the heart and its structures remains a valuable tool for studies of human cardiovascular conditions. The rat's larynx has been used in experimentations that involve inhalation toxicity, allograft rejection, and irradiation responses. One experiment described four features of

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6396-593: The black rat , his mention of a large percentage of albino specimens—not uncommon among wild populations of brown rats—adds credibility to this conclusion. Reliable reports dating to the 18th century document the presence of the brown rat in Ireland in 1722, England in 1730, France in 1735, Germany in 1750, and Spain in 1800, becoming widespread during the Industrial Revolution . It did not reach North America until around 1750–1755. As it spread from Asia,

6519-407: The brain (primarily in the temporal lobe ). Like touch , audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation . There are three main components of the human auditory system : the outer ear, the middle ear, and the inner ear. The outer ear includes the pinna , the visible part of the ear, as well as

6642-415: The brown rat or wharf rat , has also been carried worldwide by ships in recent centuries. The ship or wharf rat has contributed to the extinction of many species of wildlife, including birds, small mammals, reptiles, invertebrates, and plants, especially on islands. True rats are omnivorous , capable of eating a wide range of plant and animal foods, and have a very high birth rate . When introduced to

6765-416: The ear canal , which terminates at the eardrum , also called the tympanic membrane. The pinna serves to focus sound waves through the ear canal toward the eardrum. Because of the asymmetrical character of the outer ear of most mammals, sound is filtered differently on its way into the ear depending on the location of its origin. This gives these animals the ability to localize sound vertically . The eardrum

6888-411: The inferior colliculus in the midbrain tectum . The inferior colliculus integrates auditory input with limited input from other parts of the brain and is involved in subconscious reflexes such as the auditory startle response . The inferior colliculus in turn projects to the medial geniculate nucleus , a part of the thalamus where sound information is relayed to the primary auditory cortex in

7011-464: The misnomer . Berkenhout gave the brown rat the binomial name Rattus norvegicus , believing it had migrated to England from Norwegian ships in 1728. By the early to the middle part of the 19th century, British academics believed that the brown rat was not native to Norway, hypothesizing (incorrectly) that it may have come from Ireland, Gibraltar or across the English Channel with William

7134-1101: The temporal lobe . Sound is believed to first become consciously experienced at the primary auditory cortex . Around the primary auditory cortex lies Wernickes area , a cortical area involved in interpreting sounds that is necessary to understand spoken words. Disturbances (such as stroke or trauma ) at any of these levels can cause hearing problems, especially if the disturbance is bilateral . In some instances it can also lead to auditory hallucinations or more complex difficulties in perceiving sound. Hearing can be measured by behavioral tests using an audiometer . Electrophysiological tests of hearing can provide accurate measurements of hearing thresholds even in unconscious subjects. Such tests include auditory brainstem evoked potentials (ABR), otoacoustic emissions (OAE) and electrocochleography (ECochG). Technical advances in these tests have allowed hearing screening for infants to become widespread. Hearing can be measured by mobile applications which includes audiological hearing test function or hearing aid application . These applications allow

7257-520: The Alberta government implemented an extremely aggressive rat control program to stop them from advancing further. A systematic detection and eradication system was used throughout a control zone about 600 kilometres (400 mi) long and 30 kilometres (20 mi) wide along the eastern border to eliminate rat infestations before the rats could spread further into the province. Shotguns, bulldozers, high explosives, poison gas, and incendiaries were used to destroy rats. Numerous farm buildings were destroyed in

7380-526: The Conqueror . As early as 1850, however, a new hypothesis of the rat's origins was beginning to develop. The British novelist Charles Dickens acknowledged this in his weekly journal, All the Year Round, writing: It is frequently called, in books and otherwise, the 'Norway rat', and it is said to have been imported into this country in a ship-load of timber from Norway. Against this hypothesis stands

7503-647: The Faroe Islands may be among the lowest recorded worldwide. Hawadax Island (formerly known as Rat Island) in Alaska is thought to have been the first island in the Aleutians to be invaded by Norway rats (the Brown rat) when a Japanese ship went aground in the 1780s. They had a devastating effect on the native bird life. An eradication program was started in 2007 and the island was declared rat-free in June 2009. Alberta

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7626-411: The North American pack rats (aka wood rats ) and a number of species loosely called kangaroo rats . Rats such as the bandicoot rat ( Bandicota bengalensis ) are murine rodents related to true rats but are not members of the genus Rattus . Male rats are called bucks ; unmated females, does , pregnant or parent females, dams ; and infants, kittens or pups . A group of rats is referred to as

7749-508: The United Kingdom, some figures show that the rat population has been rising, with estimations that 81 million rats reside in the UK Those figures would mean that there are 1.3 rats per person in the country. High rat populations in the UK are often attributed to the mild climate, which allow them higher survival rates during the winter. With the increase in global temperature and glacier retreat, it

7872-406: The ability to hear more sensitively due to a well-developed, bony connection between the ear and their swim bladder. This "aid to the deaf" for fishes appears in some species such as carp and herring . Human perception of audio signal time separation has been measured to less than 10 microseconds (10μs). This does not mean that frequencies above 100 kHz are audible, but that time discrimination

7995-581: The age of 7 days, by 14 days old they significantly reduce ultrasound production around male rats as a defensive response. Adult rats will emit ultrasonic vocalizations in response to predators or perceived danger; the frequency and duration of such cries depends on the sex and reproductive status of the rat. The female rat also emit ultrasonic vocalizations during mating. Rats may also emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, before receiving morphine , or mating, and when tickled. The vocalization, described as

8118-432: The air warm as a heat-conserving function. Just like elderly rats are commonly groomed and nursed by their companions, nestling rats especially depend on heat from their mother, since they cannot regulate their own temperature. Other forms of interaction include: crawling under, which is literally the act of crawling underneath one another (this is common when the rat is feeling ill and helps them breathe); walking over to find

8241-567: The air, or “sound”. Charles Henry Turner was the first scientist to formally show this phenomenon through rigorously controlled experiments in ants. Turner ruled out the detection of ground vibration and suggested that other insects likely have auditory systems as well. Many insects detect sound through the way air vibrations deflect hairs along their body. Some insects have even developed specialized hairs tuned to detecting particular frequencies, such as certain caterpillar species that have evolved hair with properties such that it resonates most with

8364-677: The banks of the Po River in Italy dive for mollusks , a practice demonstrating social learning among members of this species. Rats on the island of Norderoog in the North Sea stalk and kill sparrows and ducks. Also preyed upon by brown rats are chicks, mice and small lizards. Examination of a wild brown rat stomachs in Germany revealed 4,000 food items, most of which were plants, although studies have shown that brown rats prefer meat when given

8487-465: The brown rat generally displaced the black rat in areas where humans lived. In addition to being larger and more aggressive, the change from wooden structures and thatched roofs to bricked and tiled buildings favored the burrowing brown rats over the arboreal black rats. In addition, brown rats eat a wider variety of foods, and are more resistant to weather extremes. In the absence of humans, brown rats prefer damp environments, such as river banks. However,

8610-449: The brown rat is found on seven of the eighteen Faroese islands, and is common in and around human habitations as well as in the wild. Although the brown rat is now common on all of the largest Faroese islands, only sparse information on the population is available in the literature. An investigation for infection with the spirochaete Leptospira interrogans did not find any infected animals, suggesting that Leptospira prevalence rates on

8733-613: The brown rat spread to other parts of the world sometime in the Middle Ages. The question of when brown rats became commensal with humans remains unsettled, but as a species, they have spread and established themselves along routes of human migration and now live almost everywhere humans are. The brown rat may have been present in Europe as early as 1553, a conclusion drawn from an illustration and description by Swiss naturalist Conrad Gesner in his book Historiae animalium , published 1551–1558. Though Gesner's description could apply to

8856-470: The brown, black, or Polynesian rat . Wild rodents, including rats, can carry many different zoonotic pathogens, such as Leptospira , Toxoplasma gondii , and Campylobacter . The Black Death is traditionally believed to have been caused by the microorganism Yersinia pestis , carried by the tropical rat flea ( Xenopsylla cheopis ), which preyed on black rats living in European cities during

8979-426: The city appointed Kathleen Corradi as the first Rat Czar , a position created to address the city's rat population. The position focuses on instituting policies measures to curb the population such as garbage regulation and additional rat trapping . In addition to sewers, rats are very comfortable living in alleyways and residential buildings, as there is usually a large and continuous food source in those areas. In

9102-621: The condition is known as rat mite dermatitis . When introduced into locations where rats previously did not exist, they can wreak an enormous degree of environmental degradation . Rattus rattus , the black rat , is considered to be one of the world's worst invasive species. Also known as the ship rat , it has been carried worldwide as a stowaway on seagoing vessels for millennia and has usually accompanied men to any new area visited or settled by human beings by sea. Rats first got to countries such as America and Australia by stowing away on ships. The similar species Rattus norvegicus ,

9225-414: The costs to the landowner or municipality. In the first year of the rat control program, 64 t (71 short tons) of arsenic trioxide were spread throughout 8,000 buildings on farms along the Saskatchewan border. However, in 1953 the much safer and more effective rodenticide warfarin was introduced to replace arsenic. Warfarin is an anticoagulant that was approved as a drug for human use in 1954 and

9348-537: The dumbo rat, a popular pet choice due to their low, saucer-shaped ears. A breeding standard exists for rat fanciers wishing to breed and show their rat at a rat show. In 1895, Clark University in Worcester, Massachusetts , established a population of domestic albino brown rats to study the effects of diet and for other physiological studies. Over the years, rats have been used in many experimental studies, adding to our understanding of genetics , diseases ,

9471-487: The eardrum. Within this chamber are the three smallest bones in the body, known collectively as the ossicles which include the malleus, incus, and stapes (also known as the hammer, anvil, and stirrup, respectively). They aid in the transmission of the vibrations from the eardrum into the inner ear, the cochlea . The purpose of the middle ear ossicles is to overcome the impedance mismatch between air waves and cochlear waves, by providing impedance matching . Also located in

9594-493: The effects of drugs , and other topics that have provided a great benefit for the health and wellbeing of humankind. The aortic arches of the rat are among the most commonly studied in murine models due to marked anatomical homology to the human cardiovascular system . Both rat and human aortic arches exhibit subsequent branching of the brachiocephalic trunk , left common carotid artery , and left subclavian artery , as well as geometrically similar, nonplanar curvature in

9717-410: The entering sound waves. The inner ear consists of the cochlea , which is a spiral-shaped, fluid-filled tube. It is divided lengthwise by the organ of Corti , which is the main organ of mechanical to neural transduction . Inside the organ of Corti is the basilar membrane , a structure that vibrates when waves from the middle ear propagate through the cochlear fluid – endolymph . The basilar membrane

9840-427: The epidemic outbreaks of the Middle Ages ; these rats were used as transport hosts. Another zoonotic disease linked to the rat is foot-and-mouth disease . Rats become sexually mature at age 6 weeks, but reach social maturity at about 5 to 6 months of age. The average lifespan of rats varies by species, but many only live about a year due to predation. The black and brown rats diverged from other Old World rats in

9963-676: The extinction of many species by accidentally introducing rats to new areas. Rats are found in nearly all areas of Earth which are inhabited by human beings. The only rat-free continent is Antarctica , which is too cold for rat survival outdoors, and its lack of human habitation does not provide buildings to shelter them from the weather. However, rats have been introduced to many of the islands near Antarctica, and because of their destructive effect on native flora and fauna, efforts to eradicate them are ongoing. In particular, Bird Island (just off rat-infested South Georgia Island ), where breeding seabirds could be badly affected if rats were introduced,

10086-556: The fact that when the brown rat had become common in this country, it was unknown in Norway, although there was a small animal like a rat, but really a lemming , which made its home there. Academics began to prefer this etymology of the brown rat towards the end of the 19th century, as seen in the 1895 text Natural History by American scholar Alfred Henry Miles : The brown rat is the species common in England, and best known throughout

10209-418: The fibers of the auditory nerve , which does produce action potentials. In this way, the patterns of oscillations on the basilar membrane are converted to spatiotemporal patterns of firings which transmit information about the sound to the brainstem . The sound information from the cochlea travels via the auditory nerve to the cochlear nucleus in the brainstem . From there, the signals are projected to

10332-461: The first to die. If a large fraction of a rat population is exterminated, the remaining rats will increase their reproductive rate, and quickly restore the old population level. The female is capable of becoming pregnant immediately after giving birth, and can nurse one litter while pregnant with another. She is able to produce and raise two healthy litters of normal size and weight without significantly changing her own food intake. However, when food

10455-467: The forests of Asia during the beginning of the Pleistocene . The characteristic long tail of most rodents is a feature that has been extensively studied in various rat species models, which suggest three primary functions of this structure: thermoregulation , minor proprioception , and a nocifensive -mediated degloving response. Rodent tails—particularly in rat models—have been implicated with

10578-411: The geographic distance from other rat populations. Many parts of the world have been populated by rats secondarily, where rats are now important invasive species that compete with and threaten local fauna. For instance, Norway rats reached North America between 1750 and 1775 and even in the early 20th century, from 1925 to 1927, 50% of ships entering the port of New York were rat infested. The brown rat

10701-451: The great majority are now linked to man-made environments, such as sewage systems. It is often said that there are as many rats in cities as people, but this varies from area to area depending on climate, living conditions, etc. Brown rats in cities tend not to wander extensively, often staying within 20 m (66 ft) of their nest if a suitable concentrated food supply is available, but they will range more widely where food availability

10824-488: The head and body. Adult weight ranges from 140 to 500 g (4.9 to 17.6 oz). Large individuals can reach 800 g (28 oz) but are not expected outside of domestic specimens. Stories of rats attaining sizes as big as cats are exaggerations, or misidentifications of larger rodents, such as the coypu and muskrat . It is common for breeding wild brown rats to weigh (sometimes considerably) less than 300 g (11 oz). The heaviest live Rattus norvegicus on record

10947-423: The high density of vascular tissue within the tail becomes exposed upon avulsion or similar injury to the structure. The degloving response is a nocifensive response, meaning that it occurs when the animal is subjected to acute pain , such as when a predator snatches the organism by the tail. Specially bred rats have been kept as pets at least since the late 19th century. Pet rats are typically variants of

11070-536: The midbelly. In addition, the medial thyroarytenoid muscle were focused at the midbelly while the lateral thyroarytenoid muscle MEPs were focused at the anterior third of the belly. The fourth and final feature that was cleared up was how the MEPs were distributed in the thyroarytenoid muscle. Laboratory rats have also proved valuable in psychological studies of learning and other mental processes (Barnett 2002), as well as to understand group behavior and overcrowding (with

11193-417: The middle ear are the stapedius muscle and tensor tympani muscle , which protect the hearing mechanism through a stiffening reflex. The stapes transmits sound waves to the inner ear through the oval window , a flexible membrane separating the air-filled middle ear from the fluid-filled inner ear. The round window , another flexible membrane, allows for the smooth displacement of the inner ear fluid caused by

11316-445: The option. In metropolitan areas, they survive mainly on discarded human food and anything else that can be eaten without negative consequences. The brown rat can breed throughout the year if conditions are suitable, with a female producing up to five litters a year. The gestation period is only 21 days, and litters can number up to 14, although seven is common. They reach sexual maturity in about five weeks. Under ideal conditions (for

11439-496: The order Rodentia, but stereotypical rats are found in the genus Rattus . Other rat genera include Neotoma (pack rats), Bandicota (bandicoot rats) and Dipodomys (kangaroo rats). Rats are typically distinguished from mice by their size. Usually the common name of a large muroid rodent will include the word "rat", while a smaller muroid's name will include "mouse". The common terms rat and mouse are not taxonomically specific. There are 56 known species of rats in

11562-722: The others' back ends. If living space becomes limited, rats may turn to aggressive behavior, which may result in the death of some animals, reducing the burden over the living space. Rats, like most mammals, also form family groups of a mother and her young. This applies to both groups of males and females. However, rats are territorial animals, meaning that they usually act aggressively towards or scared of strange rats. Rats will fluff up their hair, hiss, squeal, and move their tails around when defending their territory. Rats will chase each other, groom each other, sleep in group nests, wrestle with each other, have dominance squabbles, communicate, and play in various other ways with each other. Huddling

11685-478: The potential source of "cryptic" SARS-CoV-2 lineages, due to unknown viral RNA fragments in sewage matching mutations previously shown to make SARS-CoV-2 more adept at rodent-based transmission. Rats are also associated with human dermatitis because they are frequently infested with blood feeding rodent mites such as the tropical rat mite ( Ornithonyssus bacoti ) and spiny rat mite ( Laelaps echidnina ), which will opportunistically bite and feed on humans, where

11808-427: The process. Initially, tons of arsenic trioxide were spread around thousands of farm yards to poison rats, but soon after the program commenced the rodenticide and medical drug warfarin was introduced, which is much safer for people and more effective at killing rats than arsenic. Forceful government control measures, strong public support and enthusiastic citizen participation continue to keep rat infestations to

11931-399: The province launched a rat-control program that included shooting, poisoning, and gassing rats, and bulldozing or burning down some rat-infested buildings. The effort was backed by legislation that required every person and every municipality to destroy and prevent the establishment of designated pests. If they failed, the provincial government could carry out the necessary measures and charge

12054-566: The publication of the rat genome sequence, and other advances, such as the creation of a rat SNP chip , and the production of knockout rats , the laboratory rat has become a useful genetic tool, although not as popular as mice . Entirely new breeds or "lines" of brown rats, such as the Wistar rat , have been bred for use in laboratories. Much of the genome of Rattus norvegicus has been sequenced. When it comes to conducting tests related to intelligence , learning, and drug abuse , rats are

12177-475: The rat population in Manhattan equals that of its human population was definitively refuted by Robert Sullivan in his book Rats but illustrates New Yorkers' awareness of the presence, and on occasion boldness and cleverness, of the rodents. New York has specific regulations for eradicating rats; multifamily residences and commercial businesses must use a specially trained and licensed rat catcher . Chicago

12300-401: The rat's larynx. The first being the location and attachments of the thyroarytenoid muscle, the alar cricoarytenoid muscle, and the superior cricoarytenoid muscle, the other of the newly named muscle that ran from the arytenoid to a midline tubercle on the cricoid. The newly named muscles were not seen in the human larynx. In addition, the location and configuration of the laryngeal alar cartilage

12423-435: The rat's tail demonstrate a higher proportion of living fibroblasts that produce the collagen for these fibers. As in humans, these tendons contain a high density of golgi tendon organs that help the animal assess stretching of muscle in situ and adjust accordingly by relaying the information to higher cortical areas associated with balance, proprioception, and movement. The characteristic tail of murids also displays

12546-429: The rat), this means that the population of females could increase by a factor of three and a half (half a litter of 7) in 8 weeks (5 weeks for sexual maturity and 3 weeks of gestation), corresponding to a population growing by a factor of 10 in just 15 weeks. As a result, the population can grow from 2 to 15,000 in a year. The maximum life span is three years, although most barely manage one. A yearly mortality rate of 95%

12669-463: The rats, of which the pilgrims also partake. Hearing (sense) Sound may be heard through solid , liquid , or gaseous matter. It is one of the traditional five senses . Partial or total inability to hear is called hearing loss . In humans and other vertebrates, hearing is performed primarily by the auditory system : mechanical waves , known as vibrations, are detected by the ear and transduced into nerve impulses that are perceived by

12792-483: The sound of buzzing wasps, thus warning them of the presence of natural enemies. Some insects possess a tympanal organ . These are "eardrums", that cover air filled chambers on the legs. Similar to the hearing process with vertebrates, the eardrums react to sonar waves. Receptors that are placed on the inside translate the oscillation into electric signals and send them to the brain. Several groups of flying insects that are preyed upon by echolocating bats can perceive

12915-623: The species brown rat , but black rats and giant pouched rats are also sometimes kept. Pet rats behave differently from their wild counterparts depending on how many generations they have been kept as pets. Pet rats do not pose any more of a risk of zoonotic diseases than pets such as cats or dogs . Tamed rats are generally friendly and can be taught to perform selected behaviors. Selective breeding has brought about different color and marking varieties in rats. Genetic mutations have also created different fur types, such as rex and hairless. Congenital malformation in selective breeding have created

13038-976: The sperm of dominant males for fertilization. In mating, female rats show a clear mating preference for unknown males versus males that they have already mated with (also known as the Coolidge effect ), and will often resume copulatory behavior when introduced to a novel sexual partner. Females also prefer to mate with males who have not experienced social stress during adolescence, and can determine which males were stressed even without any observed difference in sexual performance of males experiencing stress during adolescence and not. Rats commonly groom each other and sleep together. Rats are said to establish an order of hierarchy, so one rat will be dominant over another one. Groups of rats tend to "play fight", which can involve any combination of jumping, chasing, tumbling, and "boxing". Play fighting involves rats going for each other's necks, while serious fighting involves strikes at

13161-419: The sponsors hope that once the rats are gone, it will regain its former status as home to the greatest concentration of seabirds in the world. The South Georgia Heritage Trust, which organized the mission describes it as "five times larger than any other rodent eradication attempted worldwide". That would be true if it were not for the rat control program in Alberta (see below). The Canadian province of Alberta

13284-425: The subject of investigation. Multiple studies have explored the thermoregulatory capacity of rodent tails by subjecting test organisms to varying levels of physical activity and quantifying heat conduction via the animals' tails. One study demonstrated a significant disparity in heat dissipation from a rat's tail relative to its abdomen. This observation was attributed to the higher proportion of vascularity in

13407-405: The surrounding environment; for example, rats will retreat to their burrows following a sudden, loud noise or while fleeing an intruder. Burrowing can therefore be described as a "pre-encounter defensive behavior", as opposed to a "post-encounter defensive behavior", such as flight, freezing, or avoidance of a threatening stimulus. Possibly originating from the plains of northern China and Mongolia,

13530-471: The tail's ability to function as a proprioceptive sensor and modulator has also been investigated. As aforementioned, the tail demonstrates a high degree of muscularization and subsequent innervation that ostensibly collaborate in orienting the organism. Specifically, this is accomplished by coordinated flexion and extension of tail muscles to produce slight shifts in the organism's center of mass , orientation, etc., which ultimately assists it with achieving

13653-449: The tail, along with ample muscle attachment sites along its plentiful caudal vertebrae , facilitate specific proprioceptive senses to help orient the rodent in a three-dimensional environment. Murids have evolved a unique defense mechanism termed degloving that allows for escape from predation through the loss of the outermost integumentary layer on the tail. However, this mechanism is associated with multiple pathologies that have been

13776-411: The tail, as well as its higher surface-area-to-volume ratio , which directly relates to heat's ability to dissipate via the skin. These findings were confirmed in a separate study analyzing the relationships of heat storage and mechanical efficiency in rodents that exercise in warm environments. In this study, the tail was a focal point in measuring heat accumulation and modulation. On the other hand,

13899-411: The tickler, resulting in the rats becoming conditioned to seek the tickling. However, as the rats age, the tendency to chirp appears to decline. Brown rats also produce communicative noises capable of being heard by humans. The most commonly heard in domestic rats is bruxing, or teeth-grinding, which is most usually triggered by happiness, but can also be 'self-comforting' in stressful situations, such as

14022-498: The user to measure hearing thresholds at different frequencies ( audiogram ). Despite possible errors in measurements, hearing loss can be detected. There are several different types of hearing loss: conductive hearing loss , sensorineural hearing loss and mixed types. Recently, the term of Aural Diversity has come into greater use, to communicate hearing loss and differences in a less negatively-associated term. There are defined degrees of hearing loss: Hearing protection

14145-541: The work of John B. Calhoun on behavioral sink ). A 2007 study found rats to possess metacognition , a mental ability previously only documented in humans and some primates . Domestic rats differ from wild rats in many ways. They are calmer and less likely to bite; they can tolerate greater crowding; they breed earlier and produce more offspring; and their brains , livers , kidneys , adrenal glands , and hearts are smaller (Barnett 2002). Brown rats are often used as model organisms for scientific research. Since

14268-575: The world. The best-known rat species are the black rat ( Rattus rattus ) and the brown rat ( Rattus norvegicus ). This group, generally known as the Old World rats or true rats, originated in Asia . Rats are bigger than most Old World mice , which are their relatives, but seldom weigh over 500 grams ( 17 + 1 ⁄ 2  oz) in the wild. The term rat is also used in the names of other small mammals that are not true rats. Examples include

14391-443: The world. It is said to have travelled from Persia to England less than two hundred years ago and to have spread from thence to other countries visited by English ships. Though the assumptions surrounding this species' origins were not yet the same as modern ones, by the 20th century, it was believed among naturalists that the brown rat did not originate in Norway, rather the species came from central Asia and (likely) China. The fur

14514-461: Was declared the "rattiest city" in the US by the pest control company Orkin in 2020, for the sixth consecutive time. It's followed by Los Angeles , New York, Washington, DC, and San Francisco . To help combat the problem, a Chicago animal shelter has placed more than 1000 feral cats (sterilized and vaccinated) outside of homes and businesses since 2012, where they hunt and catch rats while also providing

14637-466: Was described. The second feature was that the way the newly named muscles appear to be familiar to those in the human larynx. The third feature was that a clear understanding of how MEPs are distributed in each of the laryngeal muscles was helpful in understanding the effects of botulinum toxin injection. The MEPs in the posterior cricoarytenoid muscle, lateral cricoarytenoid muscle, cricothyroid muscle, and superior cricoarytenoid muscle were focused mostly at

14760-571: Was first observed on the Faroe Islands in 1768. It is thought that the first individuals arrived on the southernmost island, Suðuroy , via the wreck of a Norwegian ship that had stranded on the Scottish Isle of Lewis on its way from Trondheim to Dublin . The drifting wreck, carrying brown rats, drifted northwards until it reached the village of Hvalba . Dispersion afterwards appears to have been fast, including all of Suðuroy within

14883-694: Was heritable in some way. Rat meat is a food that, while taboo in some cultures, is a dietary staple in others. Rats have been used as working animals. Tasks for working rats include the sniffing of gunpowder residue, demining , acting and animal-assisted therapy . Rats have a keen sense of smell and are easy to train. These characteristics have been employed, for example, by the Belgian non-governmental organization APOPO , which trains rats (specifically African giant pouched rats ) to detect landmines and diagnose tuberculosis through smell. Rats have long been considered deadly pests. Once considered

15006-598: Was originally called the "Hanover rat" by people wishing to link problems in 18th-century England with the House of Hanover . It is not known for certain why the brown rat is named Rattus norvegicus (Norwegian rat), as it did not originate from Norway. However, the English naturalist John Berkenhout , author of the 1769 book Outlines of the Natural History of Great Britain , is most likely responsible for popularizing

15129-688: Was questioned, but provincial government rat control specialists brought in excavating machinery, dug out, shot, and poisoned 147 rats in the landfill, and no live rats were found thereafter. In 2013, the number of rat infestations in Alberta dropped to zero again. Alberta defines an infestation as two or more rats found at the same location, since a single rat cannot reproduce. About a dozen single rats enter Alberta in an average year and are killed by provincial rat control specialists before they can reproduce. Only zoos, universities, and research institutes are allowed to keep caged rats in Alberta, and possession of unlicensed rats, including fancy rats by anyone else

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