46 Rats use their burrows to escape from perceived threats in the surrounding environment; for example, rats will retreat to their burrows following a sudden, loud noise or while fleeing an intruder. 49 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. Distribution and habitat edit possibly originating from the plains of Asia, northern China and Mongolia, 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. 53 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 15511558. 54 Though Gesner's description could apply to 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. 55 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, 55 becoming widespread during the Industrial revolution. 56 It did not reach North America until around 17501755.
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45 system sparknotes Huddling is an additional important part of rat socialization. Huddling is often supposed to have a heat-conserving function. Nestling rats especially depend on heat from their mother, since they cannot regulate their own temperature. Huddling is an extreme form of herding. Other forms of interaction include: crawling under, which is literally the act of crawling underneath one another; walking over, 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. 44 Burrowing edit rats are known to burrow extensively, both in the wild and in captivity, if given access to a suitable substrate. 46 Rats generally begin a new burrow adjacent to an object or structure, as this provides a sturdy "roof" for the section of the burrow nearest to the ground's surface. 47 Burrows usually develop to eventually include multiple levels of tunnels, as well as a secondary entrance. 46 Older male rats will generally not burrow, while young males and females will burrow vigorously. 46 48 Burrows provide rats with shelter and food storage, as well as safe, thermo-regulated nest sites.
41 Rats are said to establish an order of thesis hierarchy, so one rat will be dominant over another one. 42 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 the others' back ends. 43 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. 44 This applies to both groups of males and females. However, rats are territorial animals, meaning that they usually act aggressively or scared of strange rats. Rats will fluff up their hair, hiss, squeal, and move their tails around when defending their territory. 45 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.
36 Multiple ejaculation also means that males essay can mate with multiple females, and they exhibit more ejaculatory series when there are several oestrous females present. 37 Males also copulate at shorter intervals than females. 37 In group mating, females often switch partners. 38 Dominant males have higher mating success and also provide females with more ejaculate, and females are more likely to use the sperm of dominant males for fertilization. 38 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. 39 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. 40 Social behavior edit rats commonly groom each other and sleep together.
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. 34 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 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. Citation needed females are capable of becoming pregnant immediately after giving birth, and can nurse one litter while pregnant with another. 35 Females are able to produce and raise two healthy litters of normal size and weight without significantly changing their own food intake. 35 However, when food is restricted, females can extend pregnancy by over two weeks, and give birth to litters of normal number and weight. 35 Mating behaviors edit males can ejaculate multiple times in a row, and this increases the likelihood of pregnancy as well as decreases the number of stillborns.
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Diet edit The brown rat is a true omnivore and will consume almost anything, but cereals form a substantial part of its diet. Brown rat eating sunflower seeds Martin Schein, founder of the swift Animal Behavior Society in 1964, studied the diet of brown rats and came to the conclusion that the most-liked foods of brown rats include scrambled eggs, macaroni and cheese, raw carrots, and cooked corn kernels. According to Schein, the least-liked foods were raw beets, peaches, and raw celery. 27 Foraging behavior is often population-specific, and varies by environment and food source. 2 Brown rats living near a hatchery in West Virginia catch fingerling fish. 28 Some colonies along the banks of the po river in Italy will dive for mollusks, 29 30 a practice demonstrating social learning among members of this species. 31 Rats on the island of Norderoog in the north sea stalk and kill sparrows and ducks.
32 Reproduction and life cycle edit 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 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. As a result, the population can grow from 2 to 15 000 in a year. 33 The maximum life span is three years, although most barely manage one. A yearly mortality rate of 95 is estimated, with predators and interspecies conflict as major causes.
The vocalization, described as a distinct "chirping has been likened to laughter, and is interpreted as an expectation of something rewarding. 25 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 the tickler, resulting in the rats becoming conditioned to seek the tickling. However, as the rats age, the tendency to chirp appears to decline.
26 Rat chirp also can be used for mosquito control. Citation needed Other ultrasonic vocalizations, including a lower-frequency 'boom' or 'whoom' noise can be produced by bucks in a calm state, when grooming or settling down to sleep. Citation needed audible communication edit 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 a visit to the vet. The noise is best described as either a quick clicking or 'burring' sound, varying from animal to animal. In addition, they commonly squeak along a range of tones from high, abrupt pain squeaks to soft, persistent 'singing' sounds during confrontations.
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Brown rats dig well, and often excavate extensive burrow systems. A 2007 study found brown rats to possess metacognition, a mental ability previously only found in humans and some primates, 16 but further analysis suggested they may have been following simple operant conditioning principles. 17 Communication edit Brown rats are owl capable of producing ultrasonic legs vocalizations. As pups, young rats use different types of ultrasonic cries to elicit and direct maternal search behavior, 18 as well as to regulate their mother's movements in the nest. 19 Although pups will produce ultrasounds around any other rats at 7 days old, by 14 days old they significantly reduce ultrasound production around male rats as a defensive response. 20 Adult rats will emit ultrasonic vocalizations in response to predators or perceived danger; 21 the frequency and duration of such cries depends on the sex and reproductive status of the rat. 22 23 The female rat will also emit ultrasonic vocalizations during mating. 24 Chirping edit rats may also emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, before receiving morphine, or mating, and when tickled.
In fact, it is common for breeding wild brown rats to weigh (sometimes considerably) less than 300 g (11 oz). 13 14 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) initial with no melanin in its eyes has both around 20/1200 vision and a terrible scattering of light within its vision. Brown rats are dichromates 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 some species cannot. 15 biology and behavior edit Brown rat skull 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.
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 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." 6 Academics began to prefer. 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." 7 Though the assumptions surrounding this species' origins were not yet the same as modern ones. 8 Description edit comparison of the physique of a black rat ( Rattus rattus ) with a brown rat ( Rattus norvegicus ) The fur is coarse and 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 (5.9.0 in) while the tail ranges in length from.5 to 24 cm (4.1.4 in therefore being shorter than the head and body. Adult weight ranges from 140 to 500 g (4.9.6 oz). Exceptionally large individuals can reportedly reach 900 to 1,000 g (32 to 35 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.
Europe and much of, north America, making it by at least this particular definition the most successful statement mammal on the planet alongside humans. 2, with rare exceptions, the brown rat lives wherever humans live, particularly in urban areas. Selective breeding of, rattus norvegicus has produced the laboratory rat, a model organism in biological research, as well as pet rats. Contents Naming and etymology edit Originally called the "Hanover rat" by people wishing to link problems in 18th century England with the house of Hanover, 3 it is not known for certain why the brown rat is named Rattus norvegicus (Norwegian rat as it did. 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 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 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 the conqueror. 4 As early as 1850, however, a new hypothesis of the rat's origins was beginning to develop.
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"Rattus norvegicus" and "Sewer Rat" redirect here. For the album, see. For the roller coaster, see. Sewer Rat (roller coaster). The brown rat rattus norvegicus also known as the common rat, street rat, sewer rat, hanover rat, norway rat, norwegian rat, parisian rat or wharf rat, is father's one of the best known and most common rats. One of the largest muroids, it is a brown or grey rodent with a head and body length of up to 28 cm (11 in) long, and a slightly shorter tail. It weighs between 140 and 500 g (4.9 and.6 oz). Thought to have originated in northern. China, this rodent has now spread to all continents except, antarctica, and is the dominant rat.