Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout 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 the world.[1]
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+1⁄2oz) in the wild.[2]
The term rat is also used in the names of other small mammals that are not true rats. Examples include the North American pack rats (aka wood rats[3]) and a number of species loosely called kangaroo rats.[3] Rats such as the bandicoot rat (Bandicota bengalensis) are murine rodents related to true rats but are not members of the genus Rattus.[4][5]
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 a mischief.[6]
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.[7] 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 the brown, black, or Polynesian rat.[8]
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.[11]
The black and brown rats diverged from other Old World rats in the forests of Asia during the beginning of the Pleistocene.[12]
Rat tails
A closeup of a rat tail
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,[13] minor proprioception, and a nocifensive-mediated degloving response.[14] Rodent tails—particularly in rat models—have been implicated with 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 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.[15] 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 the subject of investigation.[citation needed]
Microscopic cross section of Rattus rattus tail, delineating tendon bundles, vasculature, and vertebral canal.
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.[16] This observation was attributed to the higher proportion of vascularity in 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.[citation needed]
On the other hand, 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.[17] 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 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.[18] Namely, cell viability tests of tendons of 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.[citation needed]
The characteristic tail of murids also displays 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.[19] Paramount among these are bacterial and viral infection, as 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.[citation needed]
Specially bred rats have been kept as pets at least since the late 19th century. Pet rats are typically variants of 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.[20] Pet rats do not pose any more of a risk of zoonotic diseases than pets such as cats or dogs.[21] 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 the dumbo rat, a popular pet choice due to their low, saucer-shaped ears.[22] A breeding standard exists for rat fanciers wishing to breed and show their rat at a rat show.[23]
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.[24] Over the years, rats have been used in many experimental studies, adding to our understanding of genetics, diseases, the effects of drugs, and other topics that have provided a great benefit for the health and wellbeing of humankind.[25]
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.[26] 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 the aortic branches.[26] Aortic arches studied in rats exhibit abnormalities similar to those of humans, including altered pulmonary arteries and double or absent aortic arches.[27] 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.[28]
The rat's larynx has been used in experimentations that involve inhalation toxicity, allograft rejection, and irradiation responses. One experiment described four features of 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 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 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.[29]
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 the work of John B. Calhoun on behavioral sink).[30][31] A 2007 study found rats to possess metacognition, a mental ability previously only documented in humans and some primates.[32][33]
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 the publication of the rat genome sequence,[34] 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.[35]
When it comes to conducting tests related to intelligence, learning, and drug abuse, rats are a popular choice due to their high intelligence, ingenuity, aggressiveness, and adaptability. Their psychology seems in many ways similar to that of humans.[36] 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.[37]
General intelligence
Early studies found evidence both for and against measurable intelligence using the "g factor" in rats.[38][39] Part of the difficulty of understanding animal cognition, generally, is determining what to measure.[40] One aspect of intelligence is the ability to learn, which can be measured using a maze like the T-maze.[40] 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 was heritable in some way.[40]
Rats have long been considered deadly pests. Once considered 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.[43] Rats have long been held up as the chief villain in the spread of the Bubonic Plague;[44] however, recent studies show that rats alone could not account for the rapid spread of the disease through Europe in the Middle Ages.[45] Still, the Centers for Disease Control does list nearly a dozen diseases[46] 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.[47] Indeed, rats in New York City are famous for their size and prevalence. The urban legend that 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.[48] New York has specific regulations for eradicating rats; multifamily residences and commercial businesses must use a specially trained and licensed rat catcher.[49]
Chicago 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.[50] 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 a deterrent simply by their presence.[51]
Rats have the ability to swim up sewer pipes into toilets.[52][53] 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.[54]
In the spread of disease
Rats can serve as zoonotic vectors for certain pathogens and thus spread disease, such as bubonic plague, Lassa fever, leptospirosis, and Hantavirus infection.[55] Researchers studying New York City wastewater have also cited rats as 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.[56]
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,[57] where the condition is known as rat mite dermatitis.[58]
As invasive species
Rat-catching, 1823, by Edwin Landseer, engraving, published by Hurst, Robinson & Co.
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.[59] 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.[60] The similar species Rattus norvegicus, the brown rat or wharf rat, has also been carried worldwide by ships in recent centuries.[61]
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 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.[62] 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 the extinction of many species by accidentally introducing rats to new areas.[63]
Rat-free areas
Rat trapped in a cage
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, is subject to special measures and regularly monitored for rat invasions.[64]
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 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".[70] That would be true if it were not for the rat control program in Alberta (see below).
The Canadian province of Alberta 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.[71]
Alberta was settled by Europeans relatively late in North American history and only became 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.[72] Immediately upon their arrival at the eastern border with Saskatchewan, 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 (400mi) long and 30 kilometres (20mi) wide along the eastern border[further explanation needed] 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 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.[73]
Forceful government control measures, strong public support and enthusiastic citizen participation continue to keep rat infestations to a minimum.[74] 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 is zero.[75]
In culture
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).[76]
Chinese zodiac pendant with 5 rats climbing ruyi, bat at top of pendantTwo mice, Vietnam Museum of Ethnology - HanoiChuột rước đèn (The mouse carries the lamp), Vietnamese Đông Hồ painting
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, 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".
Indigenous rats are allowed to run freely throughout the Karni Mata Temple.
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 the rats, of which the pilgrims also partake.
European cultures
European associations with the rat are generally negative. For instance, "Rats!" is used as a substitute for various vulgar interjections in the English language. These associations do not draw, per se, from any biological or behavioral trait of the rat, but possibly from the association of rats (and fleas) with the 14th-century medieval plague called the Black Death. Rats are seen as vicious, unclean, parasitic animals that steal food and spread disease. In 1522, the rats in Autun, France were charged and put on trial for destroying crops.[78] However, some people in European cultures keep rats as pets and conversely find them to be tame, clean, intelligent, and playful.
Rats are often used in scientific experiments; animal rights activists allege the treatment of rats in this context is cruel. The term "lab rat" is used, typically in a self-effacing manner, to describe a person whose job function requires them to spend a majority of their work time engaged in bench-level research (such as postgraduate students in the sciences).
Terminology
Rats are frequently blamed for damaging food supplies and other goods, or spreading disease. Their reputation has carried into common parlance: in the English language, "rat" is often an insult or is generally used to signify an unscrupulous character; it is also used, as a synonym for the term nark, to mean an individual who works as a police informant or who has turned state's evidence. Writer/director Preston Sturges created the humorous alias "Ratskywatsky" for a soldier who seduced, impregnated, and abandoned the heroine of his 1944 film, The Miracle of Morgan's Creek. It is a term (noun and verb) in criminal slang for an informant – "to rat on someone" is to betray them by informing the authorities of a crime or misdeed they committed. Describing a person as "rat-like" usually implies he or she is unattractive and suspicious.
Among trade unions, the word "rat" is also a term for nonunion employers or breakers of union contracts, and this is why unions use inflatable rats.[79]
Depictions of rats in fiction are historically inaccurate and negative. The most common falsehood is the squeaking almost always heard in otherwise realistic portrayals (i.e. nonanthropomorphic). While the recordings may be of actual squeaking rats, the noise is uncommon – they may do so only if distressed, hurt, or annoyed. Normal vocalizations are very high-pitched, well outside the range of human hearing. Rats are also often cast in vicious and aggressive roles when in fact, their shyness helps keep them undiscovered for so long in an infested home.
Selfish helpfulness —those willing to help for a price— has also been attributed to fictional rats.[80] Templeton, from E. B. White's Charlotte's Web, repeatedly reminds the other characters that he is only involved because it means more food for him, and the cellar-rat of John Masefield's The Midnight Folk requires bribery to be of any assistance.
By contrast, the rats appearing in the Doctor Dolittle books tend to be highly positive and likeable characters, many of whom tell their remarkable life stories in the Mouse and Rat Club established by the animal-loving doctor.
Some fictional works use rats as the main characters. Notable examples include the society created by O'Brien's Mrs. Frisby and the Rats of NIMH, and others include Doctor Rat, and Rizzo the Rat from The Muppets. Pixar's 2007 animated film Ratatouille is about a rat described by Roger Ebert as "earnest... lovable, determined, [and] gifted" who lives with a Parisian garbage-boy-turned-chef.[81]
In Harry Turtledove's science fiction novel Homeward Bound, humans unintentionally introduce rats to the ecology at the home world of an alien race which previously invaded Earth and introduced some of its own fauna into its environment. A. Bertram Chandler pitted the space-bound protagonist of a long series of novels, Commodore Grimes, against giant, intelligent rats who took over several stellar systems and enslaved their human inhabitants. "The Stainless Steel Rat" is nickname of the (human) protagonist of a series of humorous science fictionnovels written by Harry Harrison.
One of the oldest and most historic stories about rats is "The Pied Piper of Hamelin", in which a rat-catcher leads away an infestation with enchanted music.[86] The piper is later refused payment, so he in turn leads away the town's children. This tale, traced to Germany around the late 13th century, has inspired adaptations in film, theatre, literature, and even opera. The subject of much research, some theories have intertwined the tale with events related to the Black Plague, in which black rats played an important role. Fictional works based on the tale that focus heavily on the rat aspect include Pratchett's The Amazing Maurice and his Educated Rodents, and Belgian graphic novel Le Bal du Rat Mort[fr] (The Ball of the Dead Rat). Furthermore, a linguistic phenomenon when a wh-expression drags with it an entire encompassing phrase to the front of the clause has been named pied-piping after "Pied Piper of Hamlin" (see also pied-piping with inversion).
The black rat, also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus Rattus, in the subfamily Murinae. It likely originated in the Indian subcontinent, but is now found worldwide.
The brown rat, 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. Thought to have originated in northern China and neighbouring areas, this rodent has now spread to all continents except Antarctica, and 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.
Rattus is a genus of muroid rodents, all typically called rats. However, the term rat can also be applied to rodent species outside of this genus.
The fancy rat is the domesticated form of Rattus norvegicus, the brown rat, and the most common species of rat kept as a pet. The name fancy rat derives from the use of the adjective fancy for a hobby, also seen in "animal fancy", a hobby involving the appreciation, promotion, or breeding of pet or domestic animals. The offspring of wild-caught specimens, having become docile after having been bred for many generations, fall under the fancy type.
Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despite the crucial roles that rodents play in nature, there are times when they need to be controlled.
The Polynesian rat, Pacific rat or little rat, or kiore, is the third most widespread species of rat in the world behind the brown rat and black rat. Contrary to its vernacular name, the Polynesian rat originated in Southeast Asia, and like its relatives has become widespread, migrating to most of Polynesia, including New Zealand, Easter Island, and Hawaii. It shares high adaptability with other rat species extending to many environments, from grasslands to forests. It is also closely associated with humans, who provide easy access to food. It has become a major pest in most areas of its distribution.
The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. Members of this subfamily are called murines. In terms of species richness, this subfamily is larger than all mammal families except the Cricetidae and Muridae, and is larger than all mammal orders except the bats and the remainder of the rodents.
Maclear's rat is an extinct large rat endemic to Christmas Island in the Indian Ocean. It was one of two species of rat native to Christmas Island, alongside the bulldog rat. Abundant, unfamiliar with and seemingly unafraid of humans, large numbers of the creatures emerged and foraged in all directions at night. Making querulous squeaks, the rats entered the Challenger expedition's tents and shelters in 1886, ran over sleepers, and upset everything in the search and fight for food. Maclear's rat might have been responsible for keeping the population of the Christmas Island red crab in check, as recent numbers of the crab are greater than in the past. It is thought that black rats inadvertently introduced by the expedition infected the Maclear's rats with a disease, which in turn could have contributed to the species' decline. The last recorded sighting was in 1903, although it is possible that Maclear's rats hybridized with black rats. A hard tick, described as an ectoparasite of Maclear's rat, is also thought to be extinct.
The lesser bandicoot rat, Sindhi rice rat, Bengal rat or Indian mole-rat is a giant rat of Southern Asia, not related to the true bandicoots which are marsupials. They can be up to 40 cm long, are considered a pest in the cereal crops and gardens of India and Sri Lanka, and emit piglike grunts when attacking. The name bandicoot is derived from the Telugu language word pandikokku, which translates loosely to "pig-rat". Like the better known rats in the genus Rattus, bandicoot rats are members of the family Muridae. Their fur is dark or (rarely) pale brown dorsally, occasionally blackish, and light to dark grey ventrally. The head-body length is around 250 mm, and the uniformly dark tail is shorter than the head-body length.
Rat-bite fever (RBF) is an acute, febrile human illness caused by bacteria transmitted by rodents, in most cases, which is passed from rodent to human by the rodent's urine or mucous secretions. Alternative names for rat-bite fever include streptobacillary fever, streptobacillosis, spirillary fever, bogger, and epidemic arthritic erythema. It is a rare disease spread by infected rodents and caused by two specific types of bacteria:
Streptobacillus moniliformis, the only reported bacteria that causes RBF in North America
Spirillum minus, common in Asia. Most cases occur in Japan, but specific strains of the disease are present in the United States, Europe, Australia, and Africa.
Laboratory rats or lab rats are strains of the rat subspecies Rattus norvegicus domestica which are bred and kept for scientific research. While less commonly used for research than laboratory mice, rats have served as an important animal model for research in psychology and biomedical science.
Seoul orthohantavirus (SEOV) is a member of the genus Orthohantavirus of rodent-borne viruses, and is one of the four hantaviruses that are known to cause Hantavirus hemorrhagic fever with renal syndrome (HFRS). It is an Old World hantavirus; a negative sense, single-stranded, tri-segmented RNA virus.
The ricefield rat is a species of rat found throughout Southeast Asia.
Rodents are mammals of the order Rodentia, which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are native to all major land masses except for Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity.
Norbormide is a toxic compound used as a rodenticide. It has several mechanisms of action, acting as a vasoconstrictor and calcium channel blocker, but is selectively toxic to rats and has relatively low toxicity to other species, due to a species specific action of opening the permeability transition pores in rat mitochondria.
Nosopsyllus fasciatus, the northern rat flea, is a species of flea found on domestic rats and house mice. Northern rat fleas are external parasites, living by hematophagy off the blood of rodents. N. fasciatus can bite humans, but they are more common parasites of rodents. Since they are associated with humans, they are common disease vectors that can spread from animals to humans. Diseases that can be spread through fleas include the plague and typhus. The rat flea is widespread due to their relationship to rodents and other vertebrates. They can be found co-infecting their host with other parasites.
Rats in New York City are widespread, as they are in many densely populated areas. They are considered a cultural symbol of the city. For a long time, the number of rats in New York City was unknown, and a common urban legend declared there were up to five times as many rats as people. However, a 2023 study estimates that there are approximately 3 million rats in New York, which is close to a third of New York's human population.
Trypanosoma lewisi is a globally distributed parasite of Rattus species and other rodents such as mice, and of kangaroo rats in America. Among these host species were two endemic species of rats: Rattus macleari and Rattus nativitatis. Both are now believed to be extinct. It is not very clear whether or not the same parasite infected both species. However, both parasites are very similar. The northern rat flea acts as the vector for the parasite, harboring the epimastigote stage in its midgut. The trypomastigote is the stage that is present in the main host, the rodent. The epimastigote form attaches itself to the rectum of the insect using its flagella to burrow through the rectal walls. The parasites also appear in the flea's feces. Ingestion of either the flea or its feces during grooming infects the host rodent with the parasites. T. lewisi is normally non-pathogenic but is known to have produced fatal infections in rats.
Rattini is a very large, diverse tribe of muroid rodents in the subfamily Murinae. They are found throughout Asia and Australasia, with a few species ranging into Europe and northern Africa. The most well-known members of this group are the true rats, several species of which have been introduced worldwide.
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↑ Eyers, Jonathan (2011). Don't Shoot the Albatross!: Nautical Myths and Superstitions. A&C Black, London, UK. ISBN978-1-4081-3131-2.
↑ MacKinnon, J. B. (September 26, 2023). "In Defense of the Rat". hakaimagazine.com. Hakai Magazine. Archived from the original on October 3, 2023. Retrieved October 8, 2023.
1 2 3 Clute, John; John Grant (March 15, 1999). The Encyclopedia of Fantasy. St. Martin's Griffin. p.642. ISBN978-0-312-19869-5.
↑ Ebert, Roger (2008). Roger Ebert's Four-Star Reviews 1967–2007. Andrews McMeel Publishing. p.637. ISBN978-0-7407-7179-8. Remy, the earnest little rat who is its hero, is such a lovable, determined, gifted rodent that I want to know what happens to him next, now that he has conquered the summit of French cuisine.
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