Rodents wiki

Rodents wiki DEFAULT

Rat

Several genera of rodents

For other uses, see Rat (disambiguation).

"Rats" redirects here. For "The Rats", see The Rats (disambiguation).

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]

Species and description

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.[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.

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.[4]

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.[5] 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.[6]

Wild rodents, including rats, can carry many different zoonotic pathogens, such as Leptospira, Toxoplasma gondii, and Campylobacter.[7] 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 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.[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.[9]

The black and brown rats diverged from other Old World rats in the forests of Asia during the beginning of the Pleistocene.[10]

Rat tails

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,[11] minor proprioception, and a nocifensive-mediated degloving response.[12] 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.[citation needed] 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]

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.[13] 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.[14] 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.[15] 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.[16] 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]

As pets

Main article: Fancy rat

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.[17] Pet rats do not pose any more of a health risk than pets such as cats or dogs.[18] 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.[19] A breeding standard exists for rat fanciers wishing to breed and show their rat at a rat show.[20]

As subjects for scientific research

Main article: Laboratory rat

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.[citation needed] 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.[citation needed]

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.[21] 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.[21] Aortic arches studied in rats exhibit abnormalities similar to those of humans, including altered pulmonary arteries and double or absent aortic arches.[22] 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.[23]

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.[24]

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).[citation needed] A 2007 study found rats to possess metacognition, a mental ability previously only documented in humans and some primates.[25][26]

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,[27] 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. 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.[citation needed]

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.[28]

General intelligence

Early studies found evidence both for and against measurable intelligence using the "g factor" in rats.[29][30] Part of the difficulty of understanding animal cognition generally, is determining what to measure.[31] One aspect of intelligence is the ability to learn, which can be measured using a maze like the T-maze.[31] 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.[31]

As food

Main article: Rat meat

Rat meat is a food that, while taboo in some cultures, is a dietary staple in others.[32]

Working rats

Main article: Working rat

Rats have been used as working animals. Tasks for working rats include the sniffing of gunpowder residue, demining, acting and animal-assisted therapy.

For odor detection

Rats have a keen sense of smell and are easy to train. These characteristics have been employed, for example, by the Belgian non-governmental organizationAPOPO, which trains rats (specifically African giant pouched rats) to detect landmines and diagnose tuberculosis through smell.[33]

As pests

Rodent Bait Station, Chennai, India

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.[34] Rats have long been held up as the chief villain in the spread of the Bubonic Plague;[35] however, recent studies show that rats alone could not account for the rapid spread of the disease through Europe in the Middle Ages.[36] Still, the Centers for Disease Control does list nearly a dozen diseases[37] 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.[38] 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.[39] New York has specific regulations for eradicating rats; multifamily residences and commercial businesses must use a specially trained and licensed rat catcher.[40]

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.[41] 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.[42]

Rats have the ability to swim up sewer pipes into toilets.[43][44] 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.[45]

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.[46]

They 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,[47] where the condition is known as rat mite dermatitis.[48]

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.[49] 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. The similar species Rattus norvegicus, the brown rat or wharf rat, has also been carried worldwide by ships in recent centuries.[citation needed]

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.[50] 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.[51]

Rat-free 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, is subject to special measures and regularly monitored for rat invasions.[52]

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 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 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".[53] 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.[54]

Alberta was settled 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.[55] 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 (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 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.[56]

Forceful government control measures, strong public support and enthusiastic citizen participation continue to keep rat infestations to a minimum.[57] 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.[58]

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).[59]

On the Isle of Man, there is a taboo against the word "rat".[60]

Chinese zodiac pendant with 5 rats climbing ruyi, bat at top of pendant

Asian cultures

Main article: Rat (zodiac)

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".

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. 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.[61]

Fiction

See also: Fancy rat § Fiction

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.

The actual portrayals of rats vary from negative to positive with a majority in the negative and ambiguous.[62] The rat plays a villain in several mouse societies; from Brian Jacques's Redwall and Robin Jarvis's The Deptford Mice, to the roles of Disney's Professor Ratigan and Kate DiCamillo's Roscuro and Botticelli. They have often been used as a mechanism in horror; being the titular evil in stories like The Rats or H.P. Lovecraft's The Rats in the Walls[62] and in films like Willard and Ben. Another terrifying use of rats is as a method of torture, for instance in Room 101 in George Orwell's Nineteen Eighty-Four or The Pit and the Pendulum by Edgar Allan Poe.

Selfish helpfulness —those willing to help for a price— has also been attributed to fictional rats.[62] 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.[63]

Mon oncle d'Amérique ("My American Uncle"), a 1980 French film, illustrates Henri Laborit's theories on evolutionary psychology and human behaviors by using short sequences in the storyline showing lab rat experiments.

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.

Wererats, therianthropic creatures able to take the shape of a rat,[64] have appeared in the fantasy or horror genre since the 1970s. The term is a neologism coined in analogy to werewolf.[citation needed] The concept has since become common in role playing games like Dungeons & Dragons[64][65][66] and fantasy fiction like the Anita Blake series.[67]

The Pied Piper

Main article: Pied Piper of Hamelin

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.[68] 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 (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).

See also

References

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Further reading

External links

Look up rat in Wiktionary, the free dictionary.
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Sours: https://en.wikipedia.org/wiki/Rat

Rodentia is the order of mammals known as rodents, characterised by a single pair of continuously growing incisors in each of the upper and lower jaws which must be kept short by gnawing.[1][2]

Forty percent of mammal species are rodents, and they are found in vast numbers on all continents other than Antarctica. Common rodents include mice, rats, squirrels, porcupines, beavers, guinea pigs, and hamsters.[1] Rodents use their sharp incisors to gnaw wood, break into food, and bite predators. Most rodents eat seeds or plants, though some have more varied diets. Some species have historically been pests, eating seeds stored by people[3] and spreading disease.[4]

Size and range of order

In terms of number of species—although not necessarily in terms of number of organisms (population) or biomass—rodents make up the largest order of mammals. With about 2,277 species of rodents (Wilson and Reeder, 2005), over 40% of mammalian species belong to the order.[5] Their success is probably due to their small size, short breeding cycle, and ability to gnaw and eat a wide variety of foods.[6]

Members of non-rodent orders, such as Chiroptera (bats), Scandentia (treeshrews), Soricomorpha (shrews and moles), Lagomorpha (hares, rabbits and pikas) and mustelidcarnivores such as weasels and mink, are sometimes confused with rodents.Template:Cn

Rodents are found in vast numbers on all continents except Antarctica, most islands, and in all habitats except oceans. They are the only nonvolant, non-marineplacental order—and in particular are the only placental order besides bats and pinnipeds—to have reached Australia without human introduction.

Characteristics

Dentition

File:Gnagarnas tandsystem, Nordisk familjebok.png
Nearly all rodents share the characteristic of dentition highly specialized for gnawing. This specialization gives rodents their name from the Latin, rodere, to gnaw.[7][8]All rodents, except Paucidentomys vermidax, have a single pair of upper and a single pair of lower incisors, followed by a gap (diastema), and then one or more molars or premolars; Paucidentomys vermidaxis unique among the rodents in that it possesses no molars or premolars, and its incisors are so specialsed, they are not for gnawing.[9]

Typical rodent incisors grow continuously and must be kept worn down by gnawing. Their anterior and lateral surfaces are covered with enamel, but the posterior surface is exposed dentine. During gnawing, the incisors grind against each other, wearing away the softer dentine, leaving the enamel edge as the blade of a chisel.[10] This ‘self-sharpening’ system is very effective and is one of the keys to the enormous success of rodents.[11] Rodents lack canines, and have a diastema between their incisors and premolars. They use their teeth for cutting wood, biting through the skin of fruit, or for defense. Nearly all rodents feed on plants, seeds in particular, but a few exceptions eat insects (grasshopper mouse, Onychomys leucogaster) or fish. Some squirrels are known to eat passerinebirds, such as cardinals and blue jays. One species, Paucidentomys vermidax, feeds primarily on worms and lacks the ability to gnaw or even chew, possessing bladelike, forked upper incisors and no molars.[12][9]

Size

Many rodents are small; the tiny African pygmy mouse, Mus minutoides,can be as small as 6 cm (2.4 in) in length and 7 g (0.25 oz) in weight at maturity, and the Baluchistan pygmy jerboa, Salpingotulus michaelis,is of roughly similar or slightly smaller dimensions. On the other hand, the largest extant rodent, the capybara, Hydrochoerus hydrochaeris,usually weighs up to 65 kg (143 lb), with exceptional specimens weighing up to 91 kg (201 lb).[13]Several enormous rodents are known from the fossil record, the largest known being Josephoartigasia monesi, which is estimated to have typically weighed about 1,000 kg (2,200 lb), and possibly up to 1,534 kg (3,382 lb)[14]or 2,586 kg (5,701 lb) in large individuals.[15]

Ecology and use by humans

Rodents are important in many ecosystems because they reproduce rapidly, and can function as food sources for predators, mechanisms for seed dispersal, and disease vectors. Humans use rodents as a source of fur, as pets, as model organisms in animal testing, for food, and even for detecting land mines.[16] Due to the wide diversity of their characteristics, some of which are considered uncommon or unique amongst mammals, rodents are used widely in research.[17] For example, the naked mole rat, Heterocephalus glaber, is the only known mammal that is poikilothermic and also does not produce the neurotransmitter substance P; it is therefore used in studies on thermoregulation and pain.

Evolution

File:Masillamys Senckenberg 2007-01.JPG

The fossil record of rodent-like mammals begins shortly after the extinction of the non-avian dinosaurs 65 million years ago, as early as the Paleocene. Some molecular clock data, however, suggest modern rodents (members of the order Rodentia) already appeared in the late Cretaceous, although other molecular divergence estimations are in agreement with the fossil record.[18][19] By the end of the Eocene epoch, relatives of beavers, dormice, squirrels, and other groups appeared in the fossil record. They originated in Laurasia, the supercontinent composed of today's North America, Europe, and Asia. Some species colonized Africa, giving rise to the earliest hystricognaths. From Africa, hystricognaths rafted to South America, an isolated continent during the Oligocene and Miocene epochs. By the Miocene, Africa collided with Asia, allowing rodents such as porcupines to spread into Eurasia. During the Pliocene, rodent fossils appeared in Australia. Although marsupials are the most prominent mammals in Australia, rodents now make up almost 25% of the continent's mammal species. Meanwhile, the Americas became joined by the Isthmus of Panama, and some rodents participated in the resulting Great American Interchange; sigmodontines surged southward and caviomorphs headed north.

Some prehistoric rodents
Castoroides, a giant beaver
Ceratogaulus, a horned burrowing rodent
Spelaeomys, a rat that grew to a large size on the island of Flores
Giant hutias, a group of rodents once found in the West Indies
Ischyromys, a primitive, squirrel-like rodent
Leithia, a giant dormouse
Neochoerus pinckneyi, a large North American capybara that weighed 100 kg (220 lb)
Josephoartigasia monesi, the largest known rodent, with an estimated weight of very roughly 1,000 kg (2,200 lb)
Phoberomys pattersoni, the second-largest known rodent, with an estimated weight of 700 kg (1,500 lb)
Telicomys, another giant South American rodent

Classification

File:Rodent species pie chart.png

Standard classification

The rodents are part of the cladesGlires (along with lagomorphs), Euarchontoglires (along with lagomorphs, primates, treeshrews, and colugos), and Boreoeutheria (along with most other placentalmammals). The order Rodentia may be divided into suborders, infraorders, superfamilies and families.

Classification scheme:

ORDER RODENTIA (from Latin, rodere, to gnaw)

  • Suborder Anomaluromorpha
    • Family Anomaluridae: scaly-tailed squirrels
    • Family Pedetidae: springhares
  • Suborder Castorimorpha
    • Superfamily Castoroidea
    • Superfamily Geomyoidea
  • Suborder Hystricomorpha
    • Family incertae sedisDiatomyidae: Laotian rock rat
    • Infraorder Ctenodactylomorphi
      • Family Ctenodactylidae: gundis
    • Infraorder Hystricognathi
      • Family Bathyergidae: African mole rats
      • Family Hystricidae: Old World porcupines
      • Family Petromuridae: dassie rat
      • Family Thryonomyidae: cane rats
      • Parvorder Caviomorpha
        • Family †Heptaxodontidae: giant hutias
        • Family Abrocomidae: chinchilla rats
        • Family Capromyidae: hutias
        • Family Caviidae: cavies, including guinea pigs and the capybara
        • Family Chinchillidae: chinchillas and viscachas
        • Family Ctenomyidae: tuco-tucos
        • Family Dasyproctidae: agoutis
        • Family Cuniculidae: pacas
        • Family Dinomyidae: pacaranas
        • Family Echimyidae: spiny rats
        • Family Erethizontidae: New World porcupines
        • Family Myocastoridae: nutria, coypu
        • Family Octodontidae: octodonts
  • Suborder Myomorpha
    • Superfamily Dipodoidea
      • Family Dipodidae: jerboas and jumping mice
    • Superfamily Muroidea
      • Family Calomyscidae: mouse-like hamsters
      • Family Cricetidae: hamsters, New World rats and mice, muskrats, voles
      • Family Muridae: true mice and rats, gerbils, spiny mice, crested rat
      • Family Nesomyidae: climbing mice, rock mice, white-tailed rat, Malagasy rats and mice
      • Family Platacanthomyidae: spiny dormice
      • Family Spalacidae: mole rats, bamboo rats, and zokors
  • Suborder Sciuromorpha
    • Family Aplodontiidae: mountain beaver
    • Family Gliridae (also Myoxidae, Muscardinidae): dormice
    • Family Sciuridae: squirrels, including chipmunks, prairie dogs, & marmots

Alternative classifications

The above taxonomy uses the shape of the lower jaw (sciurognath or hystricognath) as the primary character. This is the most commonly used approach for dividing the order into suborders. Many older references emphasize the zygomasseteric system (suborders Protrogomorpha, Sciuromorpha, Hystricomorpha, and Myomorpha).

Several molecular phylogenetic studies have used gene sequences to determine the relationships among rodents, but these studies have yet to produce a single, consistent and well-supported taxonomy. Some clades have been consistently produced, such as:

  • Ctenohystrica contains:
    • Ctenodactylidae (gundis)
    • Hystricognathi containing:
      • Hystricidae
      • An unnamed clade containing:
  • An unnamed clade containing:
    • Gliridae
    • Sciuroidea containing:
  • Myodonta includes:

The positions of the Castoridae, Geomyoidea, Anomaluridae, and Pedetidae are still being debated.

Monophyly or polyphyly?

In 1991, a paper submitted to Nature proposed that caviomorphs should be reclassified as a separate order (similar to Lagomorpha), based on an analysis of the amino acid sequences of guinea pig proteins.[20] This hypothesis was refined in a 1992 paper, which asserted the possibility that caviomorphs may have diverged from myomorphs

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Rodent

Order of mammals

Rodent
Rodent collage.jpg
Clockwise from top left: capybara, springhare, golden-mantled ground squirrel, house mouse and North American beaver representing the suborders Hystricomorpha, Anomaluromorpha, Sciuromorpha, Myomorpha, and Castorimorpha, respectively.
Scientific classificatione
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Simplicidentata
Order: Rodentia
Bowdich, 1821
Suborders

Anomaluromorpha
Castorimorpha
Hystricomorpha (incl. Caviomorpha)
Myomorpha
Sciuromorpha

Rodent range.png
Combined range of all rodent species (not including introduced populations)

Rodents (from Latinrodere, 'to gnaw') are mammals of the orderRodentia (), 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 New Zealand, Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity.

Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial habitat, including human-made environments. Species can be arboreal, fossorial (burrowing), saltatorial/richochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only a single upper and lower pair of ever-growing incisors. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, and hamsters. Rabbits, hares, and pikas, whose incisors also grow continually (but have two pairs of upper incisors instead of one), were once included with them, but are now considered to be in a separate order, the Lagomorpha. Nonetheless, Rodentia and Lagomorpha are sister groups, sharing a single common ancestor and forming the clade of Glires.

Most rodents are small animals with robust bodies, short limbs, and long tails. They use their sharp incisors to gnaw food, excavate burrows, and defend themselves. Most eat seeds or other plant material, but some have more varied diets. They tend to be social animals and many species live in societies with complex ways of communicating with each other. Mating among rodents can vary from monogamy, to polygyny, to promiscuity. Many have litters of underdeveloped, altricial young, while others are precocial (relatively well developed) at birth.

The rodent fossil record dates back to the Paleocene on the supercontinent of Laurasia. Rodents greatly diversified in the Eocene, as they spread across continents, sometimes even crossing oceans. Rodents reached both South America and Madagascar from Africa and, until the arrival of Homo sapiens, were the only terrestrial placental mammals to reach and colonize Australia.

Rodents have been used as food, for clothing, as pets, and as laboratory animals in research. Some species, in particular, the brown rat, the black rat, and the house mouse, are serious pests, eating and spoiling food stored by humans and spreading diseases. Accidentally introduced species of rodents are often considered to be invasive and have caused the extinction of numerous species, such as island birds, the dodo being an example, previously isolated from land-based predators.

Characteristics[edit]

Drawing of typical rodent tooth system: The front surface of the incisorsis hard enamel, whereas the rear is softer dentine. The act of chewing wears down the dentine, leaving a sharp, chisel-like edge.

The distinguishing feature of the rodents is their pairs of continuously growing, razor-sharp, open-rooted incisors.[1] These incisors have thick layers of enamel on the front and little enamel on the back.[2] Because they do not stop growing, the animal must continue to wear them down so that they do not reach and pierce the skull. As the incisors grind against each other, the softer dentine on the rear of the teeth wears away, leaving the sharp enamel edge shaped like the blade of a chisel.[3] Most species have up to 22 teeth with no canines or anterior premolars. A gap, or diastema, occurs between the incisors and the cheek teeth in most species. This allows rodents to suck in their cheeks or lips to shield their mouth and throat from wood shavings and other inedible material, discarding this waste from the sides of their mouths.[4] Chinchillas and guinea pigs have a high-fiber diet; their molars have no roots and grow continuously like their incisors.[5]

In many species, the molars are relatively large, intricately structured, and highly cusped or ridged. Rodent molars are well equipped to grind food into small particles.[1] The jaw musculature is strong. The lower jaw is thrust forward while gnawing and is pulled backwards during chewing.[2] Rodent groups differ in the arrangement of the jaw muscles and associated skull structures, both from other mammals and amongst themselves. The Sciuromorpha, such as the eastern grey squirrel, have a large deep masseter, making them efficient at biting with the incisors. The Myomorpha, such as the brown rat, have enlarged temporalis muscles, making them able to chew powerfully with their molars. The Hystricomorpha, such as the guinea pig, have larger superficial masseter muscles and smaller deep masseter muscles than rats or squirrels, possibly making them less efficient at biting with the incisors, but their enlarged internal pterygoid muscles may allow them to move the jaw further sideways when chewing.[6] The cheek pouch is a specific morphological feature used for storing food and is evident in particular subgroups of rodents like kangaroo rats, hamsters, chipmunks and gophers which have two bags that may range from the mouth to the front of the shoulders.[7] True mice and rats do not contain this structure but their cheeks are elastic due to a high degree of musculature and innervation in the region.[8]

Volume rendering of a mouse skull (CT) using shear warp algorithm

While the largest species, the capybara, can weigh as much as 66 kg (146 lb), most rodents weigh less than 100 g (3.5 oz). Rodents have wide-ranging morphologies, but typically have squat bodies and short limbs.[1] The fore limbs usually have five digits, including an opposable thumb, while the hind limbs have three to five digits. The elbow gives the forearms great flexibility.[3] The majority of species are plantigrade, walking on both the palms and soles of their feet, and have claw-like nails. The nails of burrowing species tend to be long and strong, while arboreal rodents have shorter, sharper nails. Rodent species use a wide variety of methods of locomotion including quadrupedal walking, running, burrowing, climbing, bipedal hopping (kangaroo rats and hopping mice), swimming and even gliding.[3]Scaly-tailed squirrels and flying squirrels, although not closely related, can both glide from tree to tree using parachute-like membranes that stretch from the fore to the hind limbs.[9] The agouti is fleet-footed and antelope-like, being digitigrade and having hoof-like nails. The majority of rodents have tails, which can be of many shapes and sizes. Some tails are prehensile, as in the Eurasian harvest mouse, and the fur on the tails can vary from bushy to completely bald. The tail is sometimes used for communication, as when beavers slap their tails on the water surface or house mice rattle their tails to indicate alarm. Some species have vestigial tails or no tails at all.[1] In some species, the tail is capable of regeneration if a part is broken off.[3]

Rodents generally have well-developed senses of smell, hearing, and vision. Nocturnal species often have enlarged eyes and some are sensitive to ultraviolet light. Many species have long, sensitive whiskers or vibrissae for touch or "whisking". Some rodents have cheek pouches, which may be lined with fur. These can be turned inside out for cleaning. In many species, the tongue cannot reach past the incisors. Rodents have efficient digestive systems, absorbing nearly 80% of ingested energy. When eating cellulose, the food is softened in the stomach and passed to the cecum, where bacteria reduce it to its carbohydrate elements. The rodent then practices coprophagy, eating its own fecal pellets, so the nutrients can be absorbed by the gut. Rodents therefore often produce a hard and dry fecal pellet.[1] In many species, the penis contains a bone, the baculum; the testes can be located either abdominally or at the groin.[3]

Sexual dimorphism occurs in many rodent species. In some rodents, males are larger than females, while in others the reverse is true. Male-bias sexual dimorphism is typical for ground squirrels, kangaroo rats, solitary mole rats and pocket gophers; it likely developed due to sexual selection and greater male-male combat. Female-bias sexual dimorphism exists among chipmunks and jumping mice. It is not understood why this pattern occurs, but in the case of yellow-pine chipmunks, males may have selected larger females due to their greater reproductive success. In some species, such as voles, sexual dimorphism can vary from population to population. In bank voles, females are typically larger than males, but male-bias sexual dimorphism occurs in alpine populations, possibly because of the lack of predators and greater competition between males.[10]

Distribution and habitat[edit]

Brown ratin a flowerbox: Some rodents thrive in human habitats.

One of the most widespread groups of mammals, rodents can be found on every continent except Antarctica. They are the only terrestrial placental mammals to have colonized Australia and New Guinea without human intervention. Humans have also allowed the animals to spread to many remote oceanic islands (e.g., the Polynesian rat).[3] Rodents have adapted to almost every terrestrial habitat, from cold tundra (where they can live under snow) to hot deserts.

Some species such as tree squirrels and New World porcupines are arboreal, while some, such as gophers, tuco-tucos, and mole rats, live almost completely underground, where they build complex burrow systems. Others dwell on the surface of the ground, but may have a burrow into which they can retreat. Beavers and muskrats are known for being semiaquatic,[1] but the rodent best-adapted for aquatic life is probably the earless water rat from New Guinea.[11] Rodents have also thrived in human-created environments such as agricultural and urban areas.[12]

Though some species are common pests for humans, rodents also play important ecological roles.[1] Some rodents are considered keystone species and ecosystem engineers in their respective habitats. In the Great Plains of North America, the burrowing activities of prairie dogs play important roles in soil aeration and nutrient redistribution, raising the organic content of the soil and increasing the absorption of water. They maintain these grassland habitats,[13] and some large herbivores such as bison and pronghorn prefer to graze near prairie dog colonies due to the increased nutritional quality of forage.[14]

Extirpation of prairie dogs can also contribute to regional and local biodiversity loss, increased seed depredation, and the establishment and spread of invasive shrubs.[13] Burrowing rodents may eat the fruiting bodies of fungi and spread spores through their feces, thereby allowing the fungi to disperse and form symbiotic relationships with the roots of plants (which usually cannot thrive without them). As such, these rodents may play a role in maintaining healthy forests.[15]

In many temperate regions, beavers play an essential hydrological role. When building their dams and lodges, beavers alter the paths of streams and rivers[16] and allow for the creation of extensive wetland habitats. One study found that engineering by beavers leads to a 33 percent increase in the number of herbaceous plant species in riparian areas.[17] Another study found that beavers increase wild salmon populations.[18]

Behavior and life history[edit]

Feeding[edit]

Most rodents are herbivorous, feeding exclusively on plant material such as seeds, stems, leaves, flowers, and roots. Some are omnivorous and a few are predators.[2] The field vole is a typical herbivorous rodent and feeds on grasses, herbs, root tubers, moss, and other vegetation, and gnaws on bark during the winter. It occasionally eats invertebrates such as insect larvae.[19] The plains pocket gopher eats plant material found underground during tunneling, and also collects grasses, roots, and tubers in its cheek pouches and caches them in underground larder chambers.[20]

The Texas pocket gopher avoids emerging onto the surface to feed by seizing the roots of plants with its jaws and pulling them downwards into its burrow. It also practices coprophagy.[21] The African pouched rat forages on the surface, gathering anything that might be edible into its capacious cheek pouches until its face bulges out sideways. It then returns to its burrow to sort through the material it has gathered and eats the nutritious items.[22]

Agouti species are one of the few animal groups that can break open the large capsules of the Brazil nut fruit. Too many seeds are inside to be consumed in one meal, so the agouti carries some off and caches them. This helps dispersal of the seeds as any that the agouti fails to retrieve are distant from the parent tree when they germinate. Other nut-bearing trees tend to bear a glut of fruits in the autumn. These are too numerous to be eaten in one meal and squirrels gather and store the surplus in crevices and hollow trees. In desert regions, seeds are often available only for short periods. The kangaroo rat collects all it can find and stores them in larder chambers in its burrow.[22]

A strategy for dealing with seasonal plenty is to eat as much as possible and store the surplus nutrients as fat. Marmots do this, and may be 50% heavier in the autumn than in the spring. They rely on their fat reserves during their long winter hibernation.[22] Beavers feed on the leaves, buds, and inner bark of growing trees, as well as aquatic plants. They store food for winter use by felling small trees and leafy branches in the autumn and immersing them in their pond, sticking the ends into the mud to anchor them. Here, they can access their food supply underwater even when their pond is frozen over.[23]

Although rodents have been regarded traditionally as herbivores, most small rodents opportunistically include insects, worms, fungi, fish, or meat in their diets and a few have become specialized to rely on a diet of animal matter. A functional-morphological study of the rodent tooth system supports the idea that primitive rodents were omnivores rather than herbivores. Studies of the literature show that numerous members of the Sciuromorpha and Myomorpha, and a few members of the Hystricomorpha, have either included animal matter in their diets or been prepared to eat such food when offered it in captivity. Examination of the stomach contents of the North American white-footed mouse, normally considered to be herbivorous, showed 34% animal matter.[24]

More specialized carnivores include the shrewlike rats of the Philippines, which feed on insects and soft-bodied invertebrates, and the Australian water rat, which devours aquatic insects, fish, crustaceans, mussels, snails, frogs, birds' eggs, and water birds.[24][25] The grasshopper mouse from dry regions of North America feeds on insects, scorpions, and other small mice, and only a small part of its diet is plant material. It has a chunky body with short legs and tail, but is agile and can easily overpower prey as large as itself.[26]

Social behavior[edit]

Rodents exhibit a wide range of types of social behavior ranging from the mammalian caste system of the naked mole-rat,[27] the extensive "town" of the colonial prairie dog,[28] through family groups to the independent, solitary life of the edible dormouse. Adult dormice may have overlapping feeding ranges, but they live in individual nests and feed separately, coming together briefly in the breeding season to mate. The pocket gopher is also a solitary animal outside the breeding season, each individual digging a complex tunnel system and maintaining a territory.[29]

Larger rodents tend to live in family units where parents and their offspring live together until the young disperse. Beavers live in extended family units typically with a pair of adults, this year's kits, the previous year's offspring, and sometimes older young.[30] Brown rats usually live in small colonies with up to six females sharing a burrow and one male defending a territory around the burrow. At high population densities, this system breaks down and males show a hierarchical system of dominance with overlapping ranges. Female offspring remain in the colony while male young disperse.[31] The prairie vole is monogamous and forms a lifelong pair bond. Outside the breeding season, prairie voles live in close proximity with others in small colonies. A male is not aggressive towards other males until he has mated, after which time he defends a territory, a female, and a nest against other males. The pair huddles together, grooms one another, and shares nesting and pup-raising responsibilities.[32]

Among the most social of rodents are the ground squirrels, which typically form colonies based on female kinship, with males dispersing after weaning and becoming nomadic as adults. Cooperation in ground squirrels varies between species and typically includes making alarm calls, defending territories, sharing food, protecting nesting areas, and preventing infanticide.[33] The black-tailed prairie dog forms large towns that may cover many hectares. The burrows do not interconnect, but are excavated and occupied by territorial family groups known as coteries. A coterie often consists of an adult male, three or four adult females, several nonbreeding yearlings, and the current year's offspring. Individuals within coteries are friendly with each other, but hostile towards outsiders.[28]

Perhaps the most extreme examples of colonial behavior in rodents are the eusocial naked mole rat and Damaraland mole rat. The naked mole rat lives completely underground and can form colonies of up to 80 individuals. Only one female and up to three males in the colony reproduce, while the rest of the members are smaller and sterile, and function as workers. Some individuals are of intermediate size. They help with the rearing of the young and can take the place of a reproductive if one dies.[27] The Damaraland mole rat is characterized by having a single reproductively active male and female in a colony where the remaining animals are not truly sterile, but become fertile only if they establish a colony of their own.[34]

Communication[edit]

Olfactory[edit]

Nepotistic species such as house mice rely on urine, feces and glandular secretions to recognize their kin.

Rodents use scent marking in many social contexts including inter- and intra-species communication, the marking of trails and the establishment of territories. Their urine provides genetic information about individuals including the species, the sex and individual identity, and metabolic information on dominance, reproductive status and health. Compounds derived from the major histocompatibility complex (MHC) are bound to several urinary proteins. The odor of a predator depresses scent-marking behavior.[35]

Rodents are able to recognize close relatives by smell and this allows them to show nepotism (preferential behavior toward their kin) and also avoid inbreeding. This kin recognition is by olfactory cues from urine, feces and glandular secretions. The main assessment may involve the MHC, where the degree of relatedness of two individuals is correlated to the MHC genes they have in common. In non-kin communication, where more permanent odor markers are required, as at territorial borders, then non-volatile major urinary proteins (MUPs), which function as pheromone transporters, may also be used. MUPs may also signal individual identity, with each male house mouse (Mus musculus) excreting urine containing about a dozen genetically encoded MUPs.[36]

House mice deposit urine, which contains pheromones, for territorial marking, individual and group recognition, and social organization.[37] Territorial beavers and red squirrels investigate and become familiar with the scents of their neighbors and respond less aggressively to intrusions by them than to those made by non-territorial "floaters" or strangers. This is known as the "dear enemy effect".[38][39]

Auditory[edit]

Many rodent species, particularly those that are diurnal and social, have a wide range of alarm calls that are emitted when they perceive threats. There are both direct and indirect benefits of doing this. A potential predator may stop when it knows it has been detected, or an alarm call can allow conspecifics or related individuals to take evasive action.[40] Several species, for example prairie dogs, have complex anti-predator alarm call systems. These species may have different calls for different predators (e.g. aerial predators or ground-based predators) and each call contains information about the nature of the precise threat.[41] The urgency of the threat is also conveyed by the acoustic properties of the call.[42]

Social rodents have a wider range of vocalizations than do solitary species. Fifteen different call-types have been recognized in adult Kataba mole rats and four in juveniles.[43] Similarly, the common degu, another social, burrowing rodent, exhibits a wide array of communication methods and has an elaborate vocal repertoire comprising fifteen different categories of sound.[44] Ultrasonic calls play a part in social communication between dormice and are used when the individuals are out of sight of each other.[45]

House mice use both audible and ultrasonic calls in a variety of contexts. Audible vocalizations can often be heard during agonistic or aggressive encounters, whereas ultrasound is used in sexual communication and also by pups when they have fallen out of the nest.[37]

Laboratory rats (which are brown rats, Rattus norvegicus) emit short, high frequency, ultrasonic vocalizations during purportedly pleasurable experiences such as rough-and-tumble play, when anticipating routine doses of morphine, during mating, and when tickled. The vocalization, described as a distinct "chirping", has been likened to laughter, and is interpreted as an expectation of something rewarding. In clinical 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 declines. Like most rat vocalizations, the chirping is at frequencies too high for humans to hear without special equipment, so bat detectors have been used for this purpose.[46]

Visual[edit]

Rodents, like all placental mammals except primates, have just two types of light receptive cones in their retina,[47] a short wavelength "blue-UV" type and a middle wavelength "green" type. They are therefore classified as dichromats; however, they are visually sensitive into the ultraviolet (UV) spectrum and therefore can see light that humans can not. The functions of this UV sensitivity are not always clear. In degus, for example, the belly reflects more UV light than the back. Therefore, when a degu stands up on its hind legs, which it does when alarmed, it exposes its belly to other degus and ultraviolet vision may serve a purpose in communicating the alarm. When it stands on all fours, its low UV-reflectance back could help make the degu less visible to predators.[48] Ultraviolet light is abundant during the day but not at night. There is a large increase in the ratio of ultraviolet to visible light in the morning and evening twilight hours. Many rodents are active during twilight hours (crepuscular activity), and UV-sensitivity would be advantageous at these times. Ultraviolet reflectivity is of dubious value for nocturnal rodents.[49]

The urine of many rodents (e.g. voles, degus, mice, rats) strongly reflects UV light and this may be used in communication by leaving visible as well as olfactory markings.[50] However, the amount of UV that is reflected decreases with time, which in some circumstances can be disadvantageous; the common kestrel can distinguish between old and fresh rodent trails and has greater success hunting over more recently marked routes.[51]

Tactile[edit]

Vibrations can provide cues to conspecifics about specific behaviors being performed, predator warning and avoidance, herd or group maintenance, and courtship. The Middle East blind mole rat was the first mammal for which seismic communication was documented. These fossorial rodents bang their head against the walls of their tunnels. This behavior was initially interpreted as part of their tunnel building behavior, but it was eventually realized that they generate temporally patterned seismic signals for long-distance communication with neighboring mole rats.[52]

Footdrumming is used widely as a predator warning or defensive action. It is used primarily by fossorial or semi-fossorial rodents.[53] The banner-tailed kangaroo rat produces several complex footdrumming patterns in a number of different contexts, one of which is when it encounters a snake. The footdrumming may alert nearby offspring but most likely conveys that the rat is too alert for a successful attack, thus preventing the snake's predatory pursuit.[52][54] Several studies have indicated intentional use of ground vibrations as a means of intra-specific communication during courtship among the Cape mole rat.[55] Footdrumming has been reported to be involved in male-male competition; the dominant male indicates its resource holding potential by drumming, thus minimizing physical contact with potential rivals.[52]

Mating strategies[edit]

The Cape ground squirrel is an example of a promiscuous rodent.

Some species of rodent are monogamous, with an adult male and female forming a lasting pair bond. Monogamy can come in two forms; obligate and facultative. In obligate monogamy, both parents care for the offspring and play an important part in their survival. This occurs in species such as California mice, oldfield mice, Malagasy giant rats and beavers. In these species, males usually mate only with their partners. In addition to increased care for young, obligate monogamy can also be beneficial to the adult male as it decreases the chances of never finding a mate or mating with an infertile female. In facultative monogamy, the males do not provide direct parental care and stay with one female because they cannot access others due to being spatially dispersed. Prairie voles appear to be an example of this form of monogamy, with males guarding and defending females within their vicinity.[56]

In polygynous species, males will try to monopolize and mate with multiple females. As with monogamy, polygyny in rodents can come in two forms; defense and non-defense. Defense polygyny involves males controlling territories that contain resources that attract females. This occurs in ground squirrels like yellow-bellied marmots, California ground squirrels, Columbian ground squirrels and Richardson's ground squirrels. Males with territories are known as "resident" males and the females that live within the territories are known as "resident" females. In the case of marmots, resident males do not appear to ever lose their territories and always win encounters with invading males. Some species are also known to directly defend their resident females and the ensuing fights can lead to severe wounding. In species with non-defense polygyny, males are not territorial and wander widely in search of females to monopolize. These males establish dominance hierarchies, with the high-ranking males having access to the most females. This occurs in species like Belding's ground squirrels and some tree squirrel species.[56]

Promiscuity, in which both males and females mate with multiple partners, also occurs in rodents. In species such as the white-footed mouse, females give birth to litters with multiple paternities. Promiscuity leads to increased sperm competition and males tend to have larger testicles. In the Cape ground squirrel, the male's testes can be 20 percent of its head-body length.[56] Several rodent species have flexible mating systems that can vary between monogamy, polygyny and promiscuity.[56]

Female rodents play an active role in choosing their mates. Factors that contribute to female preference may include the size, dominance and spatial ability of the male.[57] In the eusocial naked mole rats, a single female monopolizes mating from at least three males.[27]

In most rodent species, such as brown rats and house mice, ovulation occurs on a regular cycle while in others, such as voles, it is induced by mating. During copulation, males of some rodent species deposit a mating plug in the female's genital opening, both to prevent sperm leakage and to protect against other males inseminating the female. Females can remove the plug and may do so either immediately or after several hours.[57]

Birth and parenting[edit]

Rodents may be born either altricial (blind, hairless and relatively underdeveloped) or precocial (mostly furred, eyes open and fairly developed) depending on the species. The altricial state is typical for squirrels and mice, while the precocial state usually occurs in species like guinea pigs and porcupines. Females with altricial young typically build elaborate nests before they give birth and maintain them until their offspring are weaned. The female gives birth sitting or lying down and the young emerge in the direction she is facing. The newborns first venture out of the nest a few days after they have opened their eyes and initially keep returning regularly. As they get older and more developed, they visit the nest less often and leave permanently when weaned.[58]

In precocial species, the mothers invest little in nest building and some do not build nests at all. The female gives birth standing and the young emerge behind her. Mothers of these species maintain contact with their highly mobile young with maternal contact calls. Though relatively independent and weaned within days, precocial young may continue to nurse and be groomed by their mothers. Rodent litter sizes also vary and females with smaller litters spend more time in the nest than those with larger litters.[58]

Two Patagonian maraswith young, an example of a monogamous and communal nesting species

Mother rodents provide both direct parental care, such as nursing, grooming, retrieving and huddling, and indirect parenting, such as food caching, nest building and protection to their offspring.[58] In many social species, young may be cared for by individuals other than their parents, a practice known as alloparenting or cooperative breeding. This is known to occur in black-tailed prairie dogs and Belding's ground squirrels, where mothers have communal nests and nurse unrelated young along with their own. There is some question as to whether these mothers can distinguish which young are theirs. In the Patagonian mara, young are also placed in communal warrens, but mothers do not permit youngsters other than their own to nurse.[59]

Infanticide exists in numerous rodent species and may be practiced by adult conspecifics of either sex. Several reasons have been proposed for this behavior, including nutritional stress, resource competition, avoiding misdirecting parental care and, in the case of males, attempting to make the mother sexually receptive. The latter reason is well supported in primates and lions but less so in rodents.[60] Infanticide appears to be widespread in black-tailed prairie dogs, including infanticide from invading males and immigrant females, as well as occasional cannibalism of an individual's own offspring.[61] To protect against infanticide from other adults, female rodents may employ avoidance or direct aggression against potential perpetrators, multiple mating, territoriality or early termination of pregnancy.[60]Feticide can also occur among rodents; in Alpine marmots, dominant females tend to suppress the reproduction of subordinates by being antagonistic towards them while they are pregnant. The resulting stress causes the fetuses to abort.[62]

Intelligence[edit]

Kangaroo rats can locate food caches by spatial memory.

Rodents have advanced cognitive abilities. They can quickly learn to avoid poisoned baits, which makes them difficult pests to deal with.[1] Guinea pigs can learn and remember complex pathways to food.[63] Squirrels and kangaroo rats are able to locate caches of food by spatial memory, rather than just by smell.[64][65]

Because laboratory mice (house mice) and rats (brown rats) are widely used as scientific models to further our understanding of biology, a great deal has come to be known about their cognitive capacities. Brown rats exhibit cognitive bias, where information processing is biased by whether they are in a positive or negative affective state.[66] For example, laboratory rats trained to respond to a specific tone by pressing a lever to receive a reward, and to press another lever in response to a different tone so as to avoid receiving an electric shock, are more likely to respond to an intermediate tone by choosing the reward lever if they have just been tickled (something they enjoy), indicating "a link between the directly measured positive affective state and decision making under uncertainty in an animal model."[67]

Laboratory (brown) rats may have the capacity for metacognition—to consider their own learning and then make decisions based on what they know, or do not know, as indicated by choices they make apparently trading off difficulty of tasks and expected rewards, making them the first animals other than primates known to have this capacity,[68][69] but these findings are disputed, since the rats may have been following simple operant conditioning principles,[70] or a behavioral economic model.[71] Brown rats use social learning in a wide range of situations, but perhaps especially so in acquiring food preferences.[72][73]

Classification and evolution[edit]

Further information: List of rodents

Evolutionary history[edit]

See also: List of extinct rodents

Dentition is the key feature by which fossil rodents are recognized and the earliest record of such mammals comes from the Paleocene, shortly after the extinction of the non-avian dinosaurs some 66 million years ago. These fossils are found in Laurasia,[74] the supercontinent composed of modern-day North America, Europe, and Asia. The divergence of Glires, a clade consisting of rodents and lagomorphs (rabbits, hares and pikas), from other placental mammals occurred within a few million years after the Cretaceous-Paleogene boundary; rodents and lagomorphs then radiated during the Cenozoic.[75] Some molecular clock data suggest modern rodents (members of the order Rodentia) had appeared by the late Cretaceous, although other molecular divergence estimations are in agreement with the fossil record.[76][77]

Rodents are thought to have evolved in Asia, where local multituberculate faunas were severely affected by the Cretaceous–Paleogene extinction event and never fully recovered, unlike their North American and European relatives. In the resulting ecological vacuum, rodents and other Glires were able to evolve and diversify, taking the niches left by extinct multituberculates. The correlation between the spread of rodents and the demise of multituberculates is a controversial topic, not fully resolved. American and European multituberculate assemblages do decline in diversity in correlation with the introduction of rodents in these areas, but the remaining Asian multituberculates co-existed with rodents with no observable replacement taking place, and ultimately both clades co-existed for at least 15 million years.[78]

The history of the colonization of the world's continents by rodents is complex. The movements of the large superfamily Muroidea (including hamsters, gerbils, true mice and rats) may have involved up to seven colonizations of Africa, five of North America, four of Southeast Asia, two of South America and up to ten of Eurasia.[79]

During the Eocene, rodents began to diversify. Beavers appeared in Eurasia in the late Eocene before spreading to North America in the late Miocene.[81] Late in the Eocene, hystricognaths invaded Africa, most probably having originated in Asia at least 39.5 million years ago.[82] From Africa, fossil evidence shows that some hystricognaths (caviomorphs) colonized South America, which was an isolated continent at the time, evidently making use of ocean currents to cross the Atlantic on floating debris.[83] Caviomorphs had arrived in South America by 41 million years ago (implying a date at least as early as this for hystricognaths in Africa),[82] and had reached the Greater Antilles by the early Oligocene, suggesting that they must have dispersed rapidly across South America.[84]

Nesomyid rodents are thought to have rafted from Africa to Madagascar 20–24 million years ago.[85] All 27 species of native Malagasy rodents appear to be descendants of a single colonization event.

By 20 million years ago, fossils recognizably belonging to the current families such as Muridae had emerged.[74] By the Miocene, when Africa had collided with Asia, African rodents such as the porcupine began to spread into Eurasia.[86] Some fossil species were very large in comparison to modern rodents and included the giant beaver, Castoroides ohioensis, which grew to a length of 2.5 m (8 ft 2 in) and weight of 100 kg (220 lb).[87] The largest known rodent was Josephoartigasia monesi, a pacarana with an estimated body length of 3 m (10 ft).[88]

The first rodents arrived in Australia via Indonesia around 5 million years ago. Although marsupials are the most prominent mammals in Australia, many rodents, all belonging to the subfamily Murinae, are among the continent's mammal species.[89] There are about fifty species of 'old endemics', the first wave of rodents to colonize the country in the Miocene and early Pliocene, and eight true rat (Rattus) species of 'new endemics', arriving in a subsequent wave in the late Pliocene or early Pleistocene. The earliest fossil rodents in Australia have a maximum age of 4.5 million years,[90] and molecular data is consistent with the colonization of New Guinea from the west during the late Miocene or early Pliocene followed by rapid diversification. A further wave of adaptive radiation occurred after one or more colonizations of Australia some 2 to 3 million years later.[91]

Rodents participated in the Great American Interchange that resulted from the joining of the Americas by formation of the Isthmus of Panama, around 3 million years ago in the Piacenzian age.[92] In this exchange, a small number of species such as the New World porcupines (Erethizontidae) headed north.[74] However, the main southward invasion of sigmodontines preceded formation of the land bridge by at least several million years, probably occurring via rafting.[93][94][95] Sigmodontines diversified explosively once in South America, although some degree of diversification may have already occurred in Central America before the colonization.[94][95]

Standard classification[edit]

The use of the order name "Rodentia" is attributed to the English traveler and naturalist Thomas Edward Bowdich (1821).[96] The Modern Latin word Rodentia is derived from rodens, present participle of rodere – "to gnaw", "eat away".[97] The hares, rabbits and pikas (order Lagomorpha) have continuously growing incisors, as do rodents, and were at one time included in the order. However, they have an additional pair of incisors in the upper jaw and the two orders have quite separate evolutionary histories.[98] The phylogeny of the rodents places them in the clades Glires, Euarchontoglires and Boreoeutheria. The cladogram below shows the inner and outer relations of Rodentia based on a 2012 attempt by Wu et al. to align the molecular clock with paleontological data:[99]

The living rodent families based on the study done by Fabre et al. 2012.[100]

The order Rodentia may be divided into suborders, infraorders, superfamilies and families. There is a great deal of parallelism and convergence among rodents caused by the fact that they have tended to evolve to fill largely similar niches. This parallel evolution includes not only the structure of the teeth, but also the infraorbital region of the skull (below the eye socket) and makes classification difficult as similar traits may not be due to common ancestry.[101][102]Brandt (1855) was the first to propose dividing Rodentia into three suborders, Sciuromorpha, Hystricomorpha and Myomorpha, based on the development of certain muscles in the jaw and this system was widely accepted. Schlosser (1884) performed a comprehensive review of rodent fossils, mainly using the cheek teeth, and found that they fitted into the classical system, but Tullborg (1899) proposed just two sub-orders, Sciurognathi and Hystricognathi. These were based on the degree of inflection of the lower jaw and were to be further subdivided into Sciuromorpha, Myomorpha, Hystricomorpha and Bathyergomorpha. Matthew (1910) created a phylogenetic tree of New World rodents but did not include the more problematic Old World species. Further attempts at classification continued without agreement, with some authors adopting the classical three suborder system and others Tullborg's two suborders.[101]

These disagreements remain unresolved, nor have molecular studies fully resolved the situation though they have confirmed the monophyly of the group and that the clade has descended from a common Paleocene ancestor. Carleton and Musser (2005) in Mammal Species of the World have provisionally adopted a five suborder system: Sciuromorpha, Castorimorpha, Myomorpha, Anomaluromorpha, and Hystricomorpha. As of 2021 the American Society of Mammalogists recognizes 34 recent families containing more than 481 genera and 2277 species.[103][104][105]

Reconstruction of the phylogenetic tree of Rodentia on the basis of their whole genomes

Order Rodentia (from Latin, rodere, to gnaw)

  • Suborder Anomaluromorpha
  • Suborder Castorimorpha
  • Suborder Hystricomorpha
  • Suborder Myomorpha
    • Superfamily Dipodoidea
    • Superfamily Muroidea
      • Family Calomyscidae: mouse-like hamsters
      • Family Cricetidae: hamsters, New World rats and mice, muskrats, voles, lemmings
      • Family Muridae: true mice and rats, gerbils, spiny mice, crested rat
      • Family Nesomyidae: climbing mice, rock mice, white-tailed rat, Malagasy rats and mice
      • Family Platacanthomyidae: spiny dormice
      • Family Spalacidae: mole rats, bamboo rats, zokors
  • Suborder Sciuromorpha

Interaction with humans[edit]

Conservation[edit]

Drawing of the critically endangered red crested soft-furred spiny rat

While rodents are not the most seriously threatened order of mammals, there are 168 species in 126 genera that are said to warrant conservation attention[106] in the face of limited appreciation by the public. Since 76 percent of rodent genera contain only one species, much phylogenetic diversity could be lost with a comparatively small number of extinctions. In the absence of more detailed knowledge of species at risk and accurate taxonomy, conservation must be based mainly on higher taxa (such as families rather than species) and geographical hot spots.[106] Several species of rice rat have become extinct since the 19th century, probably through habitat loss and the introduction of alien species.[107] In Colombia, the brown hairy dwarf porcupine was recorded from only two mountain localities in the 1920s, while the red crested soft-furred spiny rat is known only from its type locality on the Caribbean coast, so these species are considered vulnerable.[108] The IUCN Species Survival Commission writes "We can safely conclude that many South American rodents are seriously threatened, mainly by environmental disturbance and intensive hunting".[109]

The "three now cosmopolitan commensal rodent pest species"[110] (the brown rat, the black rat and the house mouse) have been dispersed in association with humans, partly on sailing ships in the Age of Exploration, and with a fourth species in the Pacific, the Polynesian rat (Rattus exulans), have severely damaged island biotas around the world. For example, when the black rat reached Lord Howe Island in 1918, over 40 percent of the terrestrial bird species of the island, including the Lord Howe fantail,[111] became extinct within ten years. Similar destruction has been seen on Midway Island (1943) and Big South Cape Island (1962). Conservation projects can with careful planning completely eradicate these pest rodents from islands using an anticoagulant rodenticide such as brodifacoum.[110] This approach has been successful on the island of Lundy in the United Kingdom, where the eradication of an estimated 40,000 brown rats is giving populations of Manx shearwater and Atlantic puffin a chance to recover from near-extinction.[112][113]

Rodents have also been susceptible to climate change, especially species living on low-lying islands. The Bramble Cay melomys, which lived in the northernmost point of land of Australia, was the first mammal species to be declared extinct as a consequence of human-caused climate change.[114]

Exploitation[edit]

Chinchilla fur coat, exhibited at the 1900 Exposition Universelle, Paris

Humanity has long used animal skins for clothing, as the leather is durable and the fur provides extra insulation.[2] The native people of North America made much use of beaver pelts, tanning and sewing them together to make robes. Europeans appreciated the quality of these and the North American fur trade developed and became of prime importance to early settlers. In Europe, the soft underfur known as "beaver wool" was found to be ideal for felting and was made into beaver hats and trimming for clothing.[115][116] Later, the coypu took over as a cheaper source of fur for felting and was farmed extensively in America and Europe; however, fashions changed, new materials became available and this area of the animal fur industry declined.[117] The chinchilla has a soft and silky coat and the demand for its fur was so high that it was nearly wiped out in the wild before farming took over as the main source of pelts.[117] The quills and guardhairs of porcupines are used for traditional decorative clothing. For example, their guardhairs are used in the creation of the Native American"porky roach" headdress. The main quills may be dyed, and then applied in combination with thread to embellish leather accessories such as knife sheaths and leather bags. Lakota women would harvest the quills for quillwork by throwing a blanket over a porcupine and retrieving the quills it left stuck in the blanket.[118]

Consumption[edit]

At least 89 species of rodent, mostly Hystricomorpha such as guinea pigs, agoutis and capybaras, are eaten by humans; in 1985, there were at least 42 different societies in which people eat rats.[119] Guinea pigs were first raised for food around 2500 B.C. and by 1500 B.C. had become the main source of meat for the Inca Empire

Sours: https://en.wikipedia.org/wiki/Rodent
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Rodentia is an order of mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must be kept short by gnawing.[1][2]

Forty-percent of mammal species are rodents, and they are found in vast numbers on all continents other than Antarctica. Common rodents include mice, rats, squirrels, chipmunks, gophers, porcupines, beavers, hamsters, gerbils, and guinea pigs.[1] Rodents have sharp incisors that they use to gnaw wood, break into food, and bite predators. Most eat seeds or plants, though some have more varied diets. Some species have historically been pests, eating human seed stores and spreading disease.

Size and range of order[]

In terms of number of species — although not necessarily in terms of number of organisms (population) or biomass — rodents make up the largest order of mammals. There are about 2,277 species of rodents (Wilson and Reeder, 2005), with over 40 percent of mammalian species belonging to the order.[3] Their success is probably due to their small size, short breeding cycle, and ability to gnaw and eat a wide variety of foods. (Lambert, 2000)

Rodents are found in vast numbers on all continents except Antarctica, most islands, and in all habitats except oceans. They are the only placental order, other than bats (Chiroptera) and Pinnipeds, to reach Australia without human introduction.

Characteristics[]

File:Bristol.zoo.capybara.arp.jpg

Many rodents are small; the tiny African pygmy mouse is only 6 cm in length and 7 grams in weight. On the other hand, the capybara can weigh up to 45 kg (100 pounds) and the extinct Phoberomys pattersoni is believed to have weighed 700 kg. The extinct Josephoartigasia monesi weighed about one ton, and the biggest could have been more than 2.5 tons.[4]

Rodents have two incisors in the upper as well as in the lower jaw which grow continuously and must be kept worn down by gnawing; this is the origin of the name, from the Latinrodere, to gnaw, and dens, dentis, tooth. These teeth are used for cutting wood, biting through the skin of fruit, or for defense. The teeth have enamel on the outside and exposed dentine on the inside, so they self-sharpen during gnawing. Rodents lack canines, and have a space between their incisors and premolars. Nearly all rodents feed on plants, seeds in particular, but there are a few exceptions which eat insects or fish. Some squirrels are known to eat passerinebirds like cardinals and blue jays.

File:Gnagarnas tandsystem, Nordisk familjebok.png

Rodents are important in many ecosystems because they reproduce rapidly, and can function as food sources for predators, mechanisms for seed dispersal, and as disease vectors. Humans use rodents as a source of fur, as pets, as model organisms in animal testing, for food, and even in detecting landmines.[5]

Members of non-rodent orders such as Chiroptera (bats), Scandentia (treeshrews), Insectivora (moles, shrews and hedgehogs), Lagomorpha (hares, rabbits and pikas) and mustelidcarnivores such as weasels and mink are sometimes confused with rodents.

Evolution[]

File:Apodemus sylvaticus.JPG

The fossil record of rodent-like mammals begins shortly after the extinction of the non-avian dinosaurs 65 million years ago, as early as the Paleocene. Some molecular clock data, however, suggests that modern rodents (members of the order Rodentia) already appeared in the late Cretaceous, although other molecular divergence estimations are in agreement with the fossil record.[6][7] By the end of the Eocene epoch, relatives of beavers, dormouse, squirrels, and other groups appeared in the fossil record. They originated in Laurasia, the formerly joined continents of North America, Europe, and Asia. Some species colonized Africa, giving rise to the earliest hystricognaths. There is, however, a minority belief in the scientific community that evidence from mitochondrial DNA indicates that the Hystricognathi may belong to a different evolutionary offshoot and therefore a different order. From there hystricognaths rafted to South America, an isolated continent during the Oligocene and Miocene epochs. By the Miocene, Africa collided with Asia, allowing rodents such as the porcupine to spread into Eurasia. During the Pliocene, rodent fossils appeared in Australia. Even though marsupials are the prominent mammals in Australia, rodents make up almost 25% of the mammals on the continent. Meanwhile, the Americas became joined and some rodents expanded into new territory; mice headed south and porcupines headed north.

Classification[]

File:Rodent species pie chart.png

Standard classification[]

The rodents are part of the clades: Glires (along with lagomorphs), Euarchontoglires (along with lagomorphs, primates, treeshrews, and colugos), and Boreoeutheria (along with most other placentalmammals). The order Rodentia may be divided into suborders, infraorders, superfamilies and families.

Classification scheme:

ORDER RODENTIA (from Latin, rodere, to gnaw)

  • Suborder Anomaluromorpha
    • Family Anomaluridae: scaly-tailed squirrels
    • Family Pedetidae: springhares
  • Suborder Castorimorpha
    • Superfamily Castoroidea
    • Superfamily Geomyoidea
      • Family Geomyidae: pocket gophers (true gophers)
      • Family Heteromyidae: kangaroo rats and kangaroo mice
  • Suborder Hystricomorpha
    • Family incertae sedisDiatomyidae: Laotian rock rat
    • Infraorder Ctenodactylomorphi
      • Family Ctenodactylidae: gundis
    • Infraorder Hystricognathi
      • Family Bathyergidae: African mole rats
      • Family Hystricidae: Old World porcupines
      • Family Petromuridae: dassie rat
      • Family Thryonomyidae: cane rats
      • Parvorder Caviomorpha
        • Family †Heptaxodontidae: giant hutias
        • Family Abrocomidae: chinchilla rats
        • Family Capromyidae: hutias
        • Family Caviidae: cavies, including guinea pigs and the capybara
        • Family Chinchillidae: chinchillas and viscachas
        • Family Ctenomyidae: tuco-tucos
        • Family Dasyproctidae: agoutis
        • Family Dinomyidae: pacaranas
        • Family Echimyidae: spiny rats
        • Family Erethizontidae: New World porcupines
        • Family Myocastoridae: nutria
        • Family Octodontidae: octodonts
  • Suborder Myomorpha
    • Superfamily Dipodoidea
      • Family Dipodidae: jerboas and jumping mice
    • Superfamily Muroidea
      • Family Calomyscidae: mouse-like hamsters
      • Family Cricetidae: hamsters, New World rats and mice, voles
      • Family Muridae: true mice and rats, gerbils, spiny mice, crested rat
      • Family Nesomyidae: climbing mice, rock mice, white-tailed rat, Malagasy rats and mice
      • Family Platacanthomyidae: spiny dormice
      • Family Spalacidae: mole rats, bamboo rats, and zokors
  • Suborder Sciuromorpha
    • Family Aplodontiidae: mountain beaver
    • Family Gliridae (also Myoxidae, Muscardinidae): dormice
    • Family Sciuridae: squirrels, including chipmunks, prairie dogs, & marmots

Alternate classifications[]

The above taxonomy uses the shape of the lower jaw (sciurognath or hystricognath) as the primary character. This is the most commonly used approach for dividing the order into suborders. Many older references emphasize the zygomasseteric system (suborders Protrogomorpha, Sciuromorpha, Hystricomorpha, and Myomorpha).

Several molecular phylogenetic studies have used gene sequences to determine the relationships among rodents, but these studies are yet to produce a single consistent and well-supportedtaxonomy. Some clades have been consistently produced such as:

  • Ctenohystrica contains:
    • Ctenodactylidae (gundis)
    • Hystricognathi containing:
      • Hystricidae
      • An unnamed clade containing:
  • An unnnamed clade contains:
    • Gliridae
    • Sciuroidea containing:

The positions of the Castoridae, Geomyoidea, Anomaluridae, and Pedetidae are still being debated.

Monophyly or polyphyly?[]

In 1991, a paper submitted to Nature proposed that caviomorphs should be reclassified as a separate order (similar to Lagomorpha), based on an analysis of the amino acid sequences of guinea pigs.[8] This hypothesis was refined in a 1992 paper, which asserted the possibility that caviomorphs may have diverged from myomorphs prior to later divergences of Myomorpha; this would mean caviomorphs, or possibly hystricomorphs, would be moved out of the rodent classification into a separate order.[9] A minority scientific opinion briefly emerged arguing that guinea pigs, degus, and other caviomorphs are not rodents,[10][11] while several papers were put forward in support of rodent monophyly.[12][13][14] Subsequent studies published since 2002, using wider taxon and gene samples, have restored consensus among mammalian biologists that the order Rodentia is monophyletic.[15][16]

See also[]

References==[]

  1. 1.01.1 rodent - Encyclopedia.com. URL accessed on November 3, 2007.
  2. Rodents: Gnawing Animals. URL accessed on November 3, 2007.
  3. Myers, Phil Rodentia. Animal Diversity Web. University of Michigan Museum of Zoology. URL accessed on 2006-05-25.
  4. Giant rat that once roamed the earth. (HTML) URL accessed on 2008-01-16.
  5. ↑includeonly>Wines, Michael. "Gambian rodents risk death for bananas", The Age, The Age Company Ltd., 2004-05-19. Retrieved on 2006-05-25. "A rat with a nose for landmines is doing its bit for humanity" Cited as coming from the New York Times in the article.
  6. Douzery, E.J.P., F. Delsuc, M.J. Stanhope, and D. Huchon (2003). Local molecular clocks in three nuclear genes: divergence times for rodents and other mammals and incompatibility among fossil calibrations. Journal of Molecular Evolution 57: S201-S213.
  7. Horner, D.S., K. Lefkimmiatis, A. Reyes, C. Gissi, C. Saccone, and G. Pesole (2007). Phylogenetic analyses of complete mitochondrial genome sequences suggest a basal divergence of the enigmatic rodent Anomalurus. BMC Evolutionary Biology 7: 16.
  8. ↑Graur, D., Hide, W. and Li, W. (1991) 'Is the guinea-pig a rodent?' Nature, 351: 649-652.
  9. ↑Li, W., Hide, W., Zharkikh, A., Ma, D. and Graur, D. (1992) 'The molecular taxonomy and evolution of the guinea pig.' Journal of Heredity, 83 (3): 174-81.
  10. ↑D'Erchia, A., Gissi, C., Pesole, G., Saccone, C. and Arnason, U. (1996) 'The guinea-pig is not a rodent.' Nature, 381 (6583): 597-600.
  11. ↑Reyes, A., Pesole, G. and Saccone, C. (2000) 'Long-branch attraction phenomenon and the impact of among-site rate variation on rodent phylogeny.' Gene, 259 (1-2): 177-87.
  12. ↑Cao, Y., Adachi, J., Yano, T. and Hasegawa, M. (1994) 'Phylogenetic place of guinea pigs: No support of the rodent-polyphyly hypothesis from maximum-likelihood analyses of multiple protein sequences.' Molecular Biology and Evolution, 11: 593-604.
  13. ↑Kuma, K. and Miyata, T. (1994) 'Mammalian phylogeny inferred from multiple protein data.' Japanese Journal of Genetics, 69 (5): 555-66.
  14. ↑Robinson-Rechavi, M., Ponger, L. and Mouchiroud, D. (2000) 'Nuclear gene LCAT supports rodent monophyly.' Molecular Biology and Evolution, 17: 1410-1412.
  15. ↑Lin, Y-H, et al. "Four new mitochondrial genomes and the increased stability of evolutionary trees of mammals from improved taxon sampling." Molecular Biology and Evolution19 (2002): 2060-2070.
  16. ↑Carleton, Michael D., and Musser, Guy G. "Order Rodentia". Mammal Species of the World, 3rd edition, 2005, vol. 2, p. 745. (Concise overview of the literature)

Further reading[]

  • Adkins, R. M. E. L. Gelke, D. Rowe, and R. L. Honeycutt. 2001. Molecular phylogeny and divergence time estimates for major rodent groups: Evidence from multiple genes. Molecular Biology and Evolution, 18:777-791.
  • Carleton, M. D. and G. G. Musser. 2005. Order Rodentia. Pp 745-752 in Mammal Species of the World A Taxonomic and Geographic Reference. Johns Hopkins University Press, Baltimore.
  • David Lambert and the Diagram Group. The Field Guide to Prehistoric Life. New York: Facts on File Publications, 1985. ISBN 0-8160-1125-7
  • Leung LKP, Peter G. Cox, Gary C. Jahn and Robert Nugent. 2002. Evaluating rodent management with Cambodian rice farmers. Cambodian Journal of Agriculture Vol. 5, pp. 21-26.
  • McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8
  • Nowak, R. M. 1999. Walker's Mammals of the World, Vol. 2. Johns Hopkins University Press, London.
  • Steppan, S. J., R. A. Adkins, and J. Anderson. 2004. Phylogeny and divergence date estimates of rapid radiations in muroid rodents based on multiple nuclear genes. Systematic Biology, 53:533-553.
  • University of California Museum of Paleontology (UCMP). 2007 "Rodentia". [1]
  • Wilson, D. E. and D. M. Reeder, eds. 2005. Mammal Species of the World A Taxonomic and Geographic Reference. Johns Hopkins University Press, Baltimore.

External Links[]

Website on African rodentia : http://projects.biodiversity.be/africanrodentia

v·d·e

Extant mammal orders by infraclass
Australosphenida

Monotremata

Metatheria

Didelphimorphia ·Paucituberculata ·Microbiotheria ·Notoryctemorphia ·Dasyuromorphia ·Peramelemorphia ·Diprotodontia

Eutheria

Afrosoricida ·Macroscelidea ·Tubulidentata ·Hyracoidea ·Proboscidea ·Sirenia ·Cingulata ·Pilosa ·Scandentia ·Dermoptera ·Primates ·Rodentia ·Lagomorpha ·Erinaceomorpha ·Soricomorpha ·Chiroptera ·Pholidota ·Carnivora ·Perissodactyla ·Artiodactyla ·Cetacea

Template:Rodents

Sours: https://psychology.wikia.org/wiki/Rodents

Wiki rodents

Wikipedia:WikiProject Rodents

Wikimedia subject-area collaboration

Welcome to WikiProject Rodents. Several Wikipedians have formed this collaboration resource and group dedicated to improving Wikipedia's coverage of Rodents and the organization of information and articles on this topic. This page and its subpages contain their suggestions and various resources; it is hoped that this project will help to focus the efforts of other Wikipedians interested in the topic.

Articles can be tagged with this project by placing {{WikiProject Rodents}} on the talk page.

Scope[edit]

All living and extinct rodents are within the scope of this WikiProject, from the familiar mice, rats, and squirrels to less familiar groups such as pacaranas, anomalures, and eomyids. The project also covers topics related to rodents, such as parasites infecting rodents, scientists studying them, and cultural depictions of rodents.

Style[edit]

Article titles[edit]

The vernacular name should only be used as the article title when it is used in a significant proportion of reliable sources and has thus entered common usage; otherwise, the scientific name should be the article title.

Capitalisation of vernacular names[edit]

Per WP:Manual of Style#Animals, plants, and other organisms, the vernacular ("common") names of genera, species, subspecies, and other classifications of rodents are not capitalised, except for the first word of a sentence, and any proper names that are part of the vernacular name. An example of the general use is black rat. Such names are given in boldface in the lead section of the article to which they directly pertain, and are linked at first occurrence in other articles. An example of the inclusion of a proper name is California ground squirrel (where "California" is a place name). Standardized breeds of rodent livestock (e.g. of guinea pigs) are conventionally capitalized (aside from any appending of the common name of the species at the end as a natural disambiguation): English Merino. Laboratory strains are usually lower case except where they contain a proper name (including a registered trademark) or an initialism-based designation: Rowett nude rat, BALB/c. When in doubt, open a discussion on the article's talk page.

Sometimes care must be taken to clarify that a specific taxon of rodent is intended, if some readers could misinterpret the passage:

  • Helpful: The state health department issued a warning about the black rat.
  • Helpful: The state health department issued a warning about black rats (Rattus rattus).
  • Confusing: The state health department issued a warning about black rats.

Remember that people may reuse Wikipedia content (including without links to other articles), and read our own articles offline, so we cannot depend on links to work in order for what we write to make sense in the immediate context.

Open tasks[edit]

Featured content lacking focal images[edit]

The following articles have been assessed as Featured Articles, but lack illustrations of the subject (although they may contain maps or images of similar species). If you can find, or create, a suitably licensed illustration or photograph, please upload to Commons and add to the article(s) to make them even better!

Article alerts[edit]

Today's featured articles

Participants[edit]

Please feel free to add yourself here, and to indicate any areas of particular interest.

  1. 6th Happiness (talk·contribs) All rodents, but my background is in the husbandry of rodents, common domestic and exotics. Also rodents in history/culture. I prefer digging up sources, rather than polishing grammar or layout.
  2. Aranae (talk·contribs) My interest really spans the whole order.
  3. Zappernapper (talk·contribs) very limited involvement, i take lots of wikibreaks. MOS, prose, and random tedium are what i usually do. work with more common species
  4. Ucucha (talk·contribs) Interested in all rodents, but primarily in muroids and not in pets.
  5. WolfmanSF (talk·contribs) I'm focusing on species of Central and South America.
  6. Meow77 (talk·contribs) I love squirrels! (I raised two) I will focus on squirrel-related topics.
  7. T.carnifex (talk·contribs) Recently dabbled in Australian native mice, mainly from arid areas.
  8. Innotata (talk·contribs) I contribute to vertebrates in general, mostly de-stubbing and the like.
  9. Degutopia (talk·contribs) I would be happy to lend a hand with anything relating to caviomorph/hystricomorph rodents, I specialise in Octodon degus.
  10. Lukasz Lukomski (talk·contribs) Mostly working on Polish Wiki (all rodents are subjects), but keeping my options open
  11. Edude7 (talk·contribs) I love rodents in general, and I like to Cleanup Articles
  12. Cwmhiraeth (talk·contribs) Rodents of central Asia, enlarging stubs etc.
  13. Ratkinzluver33 (talk·contribs) I've been a huge fan of rodents for a while now. I'd love to clean up some messy pages :).
  14. Puffin (talk·contribs) I like rodents, I have already made Djungarian Hamster a GA and I plan to improve more rodent related articles.
  15. Lhynard (talk·contribs) I love rodents. I have owned gerbils and hamsters and so will likely make edits on such articles. I am a good copyeditor; I am not that knowledgeable about zoology, though I am a scientist in real life.
  16. Altaïr (talk·contribs) I find rodents in general interesting, but I don't own any as pets, since I have a cat. I will probably mainly polish grammar, layout and spelling, and I have a good understanding on Wikicode. I'll do whatever fixing that is needed on those matters. 17:09, 9 November 2012 (UTC)[]
  17. DegupediaDE (talk·contribs) Rodents are my passion and how they live in wild. My main interest is to improve the quality of the used sources. My focus is on insular, Mediterranean and semi-arid species from Africa, Europe, South America (Chile, Argentina) and Australia.
  18. Felixthehamster (talk·contribs) I used to have a pet hamster (sadly the hamster has since died). But I am still much fascinated by hamsters, philosophy, and philosophical hamsters.
  19. Bluerasberry (talk·contribs)
  20. Gaff (talk·contribs) (Mammals of Pacific Northwest of North America. Most are rodents.) 05:12, 12 December 2014 (UTC)[]
  21. Nerwign (talk·contribs) (I am interested in helping expand and improve information on domestic guinea pigs.) 22:52, 27 November 2017 (UTC)[]
  22. RodentGod288 (talk·contribs) I am working on rodents that I have seen near the Grand Canyon, I have added many things to "Cliff Chipmunk" and "Kaibab Squirrel" I hope that I am a help to you.
  23. SMcCandlish ☺☏¢ ≽ʌⱷ҅ʌ≼  (landraces & formal breeds/strains; coloration genetics; fancy mouse/fancy rat activities; and system-wide cleanup/consistency.) 21:49, 10 June 2015 (UTC)
  24. Mintyfrills (talk·contribs) I'm passionate about rodents, especially spreading awareness about proper care. I have a syrian hamster and mouse currently. Been editing the pages about hamster care. I'm researching rodents kept as pets. 3 July 2020
  25. TheLastClassicist1750 (talk·contribs) I am fascinated by all rodents; I hope to help out here mostly with small contributions, such as copy-editing. 22:50, 27 February 2021 (UTC)[]

Articles[edit]

There is currently a proposed guideline on rating importance to this wikiproject over a Wikipedia:WikiProject Rodents/Assessment

Recognized content[edit]

Featured articles[edit]

  1. Rodent
  2. Guinea pig
  3. Lundomys
  4. Mindomys
  5. Noronhomys
  6. Pseudoryzomys
  7. Oryzomys gorgasi
  8. Oryzomys dimidiatus
  9. Marsh rice rat
  10. Eremoryzomys

Good articles[edit]

  1. Carletonomys
  2. Capybara
  3. Chuck E. Cheese's
  4. Ekbletomys
  5. Fancy rat
  6. Muskrat
  7. Oecomys sydandersoni
  8. Oryzomys peninsulae
  9. Pikachu
  10. The Itchy & Scratchy Show
  11. Oryzomys nelsoni
  12. Oryzomys albiventer
  13. Euryoryzomys emmonsae
  14. Tachyoryctes rex
  15. Akodon caenosus
  16. Oryzomys anoblepas
  17. Oryzomys antillarum
  18. Holochilus primigenus
  19. Megalomys audreyae
  20. Eastern chipmunk -delisted
  21. Florida mouse
  22. Djungarian hamster
  23. Campbell's dwarf hamster
  24. Camas pocket gopher
  25. Gray-tailed vole

DYKs (Did You Know)s[edit]

  1. Murinae – 23 December 2004
  2. Laotian Rock Rat – 25 April 2005
  3. Blesmol – 18 September, 2005
  4. Meriones – 2 December 2006
  5. Desmarest's Hutia – 1 April 2007
  6. Shrewlike rat – 12 May 2007
  7. Pseudohydromys germani – 2 April 2008
  8. Nicaraguan Rice Rat – 8 July 2009
  9. Brazilian False Rice Rat – 9 August 2009
  10. Large Mindoro Forest Mouse – 21 August 2009
  11. Carletonomys – 10 September 2009
  12. Oryzomys hypenemus – 28 September 2009
  13. Megalomys audreyae – 9 October 2009
  14. Lund's Amphibious Rat – 13 October 2009
  15. Rodents of the Caribbean – 14 October 2009
  16. Holochilus primigenus – 16 October 2009
  17. Oryzomys anoblepas – 4 November 2009
  18. Nephelomys and 13 others – 8 November 2009
  19. Chilean Climbing Mouse – 8 November 2009
  20. Noronhomys – 20 November 2009
  21. Oryzomyini – 10 December 2009
  22. Oecomys sydandersoni – 12 December 2009
  23. Thomasomys ucucha & Oxymycterus hucucha – 15 December 2009
  24. Oryzomys peninsulae – 24 December 2009
  25. Interdigital webbing – 29 December 2009
  26. Oryzomys gorgasi – 4 January 2010
  27. Posterolateral palatal pits – 23 January 2010
  28. Hunter-Schreger band – 24 January 2010
  29. Zygomatic plate – 25 January 2010
  30. Abrotrichini – 25 January 2010
  31. Pebble-mound mouse – 26 January 2010
  32. Eastern chipmunk – 2 February 2010
  33. Eastern harvest mouse – 9 February 2010
  34. Calomys cerqueirai – 9 February 2010
  35. Florida mouse – 11 February 2010
  36. Oldfield mouse – 22 February 2010
  37. Key Largo Woodrat – 22 February 2010
  38. Sciurini – 1 March 2010
  39. Mindomys – 4 March 2010
  40. Oryzomys albiventer – 12 March 2010
  41. Marsh rice rat – 15 March 2010
  42. Muroid molar – 15 March 2010
  43. Oryzomys nelsoni – 22 March 2010
  44. Euryoryzomys emmonsae – 23 March 2010
  45. Tachyoryctes rex – 1 April 2010
  46. Akodon caenosus – 5 April 2010
  47. Ungual tufts – 8 April 2010
  48. Skrjabinoclava kinsellai – 9 April 2010
  49. Oryzomys couesi – 10 April 2010
  50. Megapedetes – 12 April 2010
  51. Mount Graham Red Squirrel – 12 April 2010
  52. Lyperosomum intermedium – 15 April 2010
  53. Eremoryzomys – 17 April 2010
  54. Isospora hammondi – 19 April 2010
  55. Oryzomys antillarum – 21 April 2010
  56. Gray-tailed vole - 12 December 2014
  57. Long-tailed vole - 21 December 2014
  58. Camas pocket gopher - 28 December 2014
  59. Creeping vole - 4 January 2015

Candidates[edit]

New articles[edit]

Please feel free to list your new Rodents-related articles here (newer articles at the top, please). Any new articles that have an interesting or unusual fact in them, are at least over 1,000 characters, don't have any dispute templates on them, and cite their sources, should be suggested for the Did you know? box on the Wikipedia Main Page.

Review and assessment[edit]

There is currently a proposed guideline on rating importance to this wikiproject over a Wikipedia:WikiProject Rodents/Assessment

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Assessment scales[edit]

For the importance scale, use the following:

For the quality scale, use the standard scale (Wikipedia:Version 1.0 Editorial Team/Assessment#Grades).

Templates[edit]

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Categories[edit]

Resources[edit]

Related projects[edit]

WikiProject parentage[edit]

Portals[edit]

Tools[edit]

Main tool page: toolserver.org
  • Reflinks - Edits bare references - adds title/dates etc. to bare references
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External watchlist[edit]

Sours: https://en.wikipedia.org/wiki/Wikipedia:WikiProject_Rodents
Learn Rodents Animals Names In English! Vocabulary List of Rodents: Rats,Mice,Squirrels \u0026 More!🐁🐀🐹 🦔

Rodent

Rodents are a very successful group of mammals. They form the orderRodentia.

They have no more than 2 incisors. These keep growing, and must be kept worn down by gnawing (eroding teeth by grinding them on something hard); this is the origin of the name, from the Latinrodere, "to gnaw", and dent, "tooth".

Most rodents are small. Examples of commonly known rodents are mice, rats, chipmunks, and squirrels. Some other small rodents sometimes kept as pets are Guinea pigs, hamsters, and gerbils. Examples of larger rodents are porcupines, beavers, and the largest living rodent, the capybara, which can grow to between 105 and 135 cm (40-55 in) in length, and weigh 35 to 65 kg (75-140 lbs).

Almost half of all mammal species are rodents. More examples of rodents are voles, prairie dogs, groundhogs, and chinchillas.

Rabbits, hares, and pikas are sometimes called rodents, because they also have teeth that keep growing. But in 1912 biologists decided to put them in a new, separate order, Lagomorpha, because they have two extra incisors in their upper jaw.

Shrews are sometimes called rodents, because they look like mice, but that is not correct. They are in the order Insectivora.

Taxonomy[change | change source]

There are more families than these. The list includes the more common families.

Related pages[change | change source]

Other websites[change | change source]

Wikimedia Commons has media related to Rodentia.
Sours: https://simple.wikipedia.org/wiki/Rodent

You will also be interested:

Mouse

Small long-tailed rodent

This article is about the animal. For the computer input device, see Computer mouse. For other uses, see Mouse (disambiguation).

"Mice" redirects here. For other uses, see Mice (disambiguation).

A mouse, plural mice, is a small mammal. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (Mus musculus). Mice are also popular as pets. In some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter.

Mice are typically distinguished from rats by their size. Generally, when a muroid rodent is discovered, its common name includes the term mouse if it is smaller, or rat if it is larger. The common terms rat and mouse are not taxonomically specific. Typical mice are classified in the genus Mus, but the term mouse is not confined to members of Mus and can also apply to species from other genera such as the deer mouse, Peromyscus.

Domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable to breeding and different conditions in the wild. The best-known strain of mouse is the white lab mouse. It has more uniform traits that are appropriate to its use in research.

Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of arthropods have been known to prey heavily upon mice. Despite this, mice populations remain plentiful. Due to its remarkable adaptability to almost any environment, the mouse is one of the most successful mammalian genera living on Earth today.

In certain contexts, mice can be considered vermin. Vermin are a major source of crop damage,[1] as they are known to cause structural damage and spread disease. Mice spread disease through their feces and are often carriers of parasites.[2] In North America, breathing dust that has come in contact with mouse excrement has been linked to hantavirus, which may lead to hantavirus pulmonary syndrome (HPS).

Primarily nocturnal[3] animals, mice compensate for their poor eyesight with a keen sense of hearing. They depend on their sense of smell to locate food and avoid predators.[4]

In the wild, mice are known to build intricate burrows. These burrows have long entrances and are equipped with escape tunnels. In at least one species, the architectural design of a burrow is a genetic trait.[5]

Types of animals known as mice

The most common mice are murines, in the same clade as common rats. They are murids, along with gerbils and other close relatives.

  • order Dasyuromorphia
  • order Rodentia
    • suborder Castorimorpha
    • suborder Anomaluromorpha
    • suborder Myomorpha

Laboratory mice

Main article: Laboratory mouse

Mice are common experimental animals in laboratory research of biology and psychology fields primarily because they are mammals, and also because they share a high degree of homology with humans. They are the most commonly used mammalianmodel organism, more common than rats. The mouse genome has been sequenced, and virtually all mouse genes have human homologs. The mouse has approximately 2.7 billion base pairs and 20 pairs of chromosomes.[6] They can also be manipulated in ways that are illegal with humans, although animal rights activists often object. A knockout mouse is a genetically modified mouse that has had one or more of its genes made inoperable through a gene knockout.

Reasons for common selection of mice are that they are small and inexpensive, have a widely varied diet, are easily maintained, and can reproduce quickly. Several generations of mice can be observed in a relatively short time. Mice are generally very docile if raised from birth and given sufficient human contact. However, certain strains have been known to be quite temperamental.

Emotions

Researchers at the Max Planck Institute of Neurobiology have confirmed that mice have a range of facial expressions. They used machine vision to spot familiar human emotions like pleasure, disgust, nausea, pain, and fear.[7][8][9]

As pets

Main article: Fancy mouse

Many people buy mice as companion pets. They can be playful, loving and can grow used to being handled. Like pet rats, pet mice should not be left unsupervised outside as they have many natural predators, including (but not limited to) birds, snakes, lizards, cats, and dogs. Male mice tend to have a stronger odor than the females. However, mice are careful groomers and as pets they never need bathing. Well looked-after mice can make ideal pets. Some common mouse care products are:

  • Cage – Usually a hamster or gerbilcage, but a variety of special mouse cages are now available. Most should have a secure door.[10]
  • Food – Special pelleted and seed-based food is available. Mice can generally eat most rodent food (for rats, mice, hamsters, gerbils, etc.)
  • Bedding – Usually made of hardwood pulp, such as aspen, sometimes from shredded, uninkedpaper or recycled virgin wood pulp. Using corn husk bedding is avoided because it promotes Aspergillusfungus, and can grow mold once it gets wet, which is rough on their feet.

Diet

In nature, mice are largely herbivores, consuming any kind of fruit or grain from plants.[11] However, mice adapt well to urban areas and are known for eating almost all types of food scraps. In captivity, mice are commonly fed commercial pelleted mouse diet. These diets are nutritionally complete, but they still need a large variety of vegetables.

Mice do not have a special appetite for cheese. They will only eat cheese for lack of better options.[12]

As food

"Pinkie" mice for sale as reptilefood

Mice are a staple in the diet of many small carnivores. Humans have eaten mice since prehistoric times. In Victorian Britain, fried mice were still given to children as a folk remedy for bed-wetting;[13] while Jared Diamond reports creamed mice being used in England as a dietary supplement during WW II rationing.[14] Mice are a delicacy throughout eastern Zambia and northern Malawi,[15] where they are a seasonal source of protein. Field rat is a popular food in Vietnam and neighboring countries.[16] In many countries, however, mouse is no longer a food item.

Prescribed cures in Ancient Egypt included mice as medicine.[17] In Ancient Egypt, when infants were ill, mice were eaten as treatment by their mothers.[18][19] It was believed that mouse eating by the mother would help heal the baby who was ill.[20][21][22][23][24]

In various countries mice are used as food[25] for pets such as snakes, lizards, frogs, tarantulas, and birds of prey, and many pet stores carry mice for this purpose.

Common terms used to refer to different ages/sizes of mice when sold for pet food are "pinkies", "fuzzies", "crawlers", "hoppers", and "adults".[26] Pinkies are newborn mice that have not yet grown fur; fuzzies have some fur but are not very mobile; and hoppers have a full coat of hair and are fully mobile but are smaller than adult mice. Mice without fur are easier for the animal to consume; however, mice with fur may be more convincing as animal feed.[citation needed] These terms are also used to refer to the various growth stages of rats (see Fancy rat).

See also

References

  1. ^Meerburg BG, Singleton GR, Leirs H (2009). "The Year of the Rat ends: time to fight hunger!". Pest Manag Sci. 65 (4): 351–2. doi:10.1002/ps.1718. PMID 19206089.
  2. ^Meerburg BG, Singleton GR, Kijlstra A (2009). "Rodent-borne diseases and their risks for public health". Crit Rev Microbiol. 35 (3): 221–70. doi:10.1080/10408410902989837. PMID 19548807. S2CID 205694138.
  3. ^Behney, W. H. (1 January 1936). "Nocturnal Explorations of the Forest Deer-Mouse". Journal of Mammalogy. 17 (3): 225–230. doi:10.2307/1374418. JSTOR 1374418.
  4. ^"Mice : The Humane Society of the United States". Archived from the original on 22 January 2010. Retrieved 15 August 2016.
  5. ^Weber, Jesse N.; Peterson, Brant K.; Hoekstra, Hopi E. (17 January 2013). "Discrete genetic modules are responsible for complex burrow evolution in Peromyscus mice". Nature. 493 (7432): 402–405. Bibcode:2013Natur.493..402W. doi:10.1038/nature11816. PMID 23325221. S2CID 4361153.
  6. ^"2002 Release: Draft Sequence of Mouse Genome". Retrieved 15 August 2016.
  7. ^"The facial expressions of mice". Max-Planck-Gesellschaft. 2 April 2020.
  8. ^"The face of a mouse reveals its emotions: study". Phys.org. 2 April 2020.
  9. ^"Mice have facial expressions, AI finds"(Video). Amaze Lab. 3 April 2020.
  10. ^Sharon L. Vanderlip (2001). Mice: Everything About History, Care, Nutrition, Handling, and Behavior. Barron's Educational Series. pp. 38–. ISBN . Retrieved 22 April 2013.
  11. ^"Mouse Info". Retrieved 15 August 2016.
  12. ^"Do mice really love cheese?". HowStuffWorks. 15 April 2015. Retrieved 27 February 2020.
  13. ^Flora Thompson, Lark Rise to Candleford (Oxford 1949) p. 504
  14. ^J Diamond, The World until Yesterday (Penguin 2012) p. 314
  15. ^Tembo, Mwizenge S. "Mice as a Delicacy: the Significance of Mice in the Diet of the Tumbuka People of Eastern Zambia". Archived from the original on 23 June 2008. Retrieved 13 August 2008.
  16. ^Gorman, James (19 June 2020). "Wildlife Trade Spreads Coronaviruses as Animals Get to Market". The New York Times.
  17. ^"BBC – History – Ancient History in depth: Health Hazards and Cures in Ancient Egypt". Retrieved 15 August 2016.
  18. ^Hart, George (1 May 2001). What life was like. Time Life Books. p. 40. ISBN .
  19. ^Encyc of Discovery Science and History. Fog City Press. 1 September 2002. p. 320. ISBN .
  20. ^"Tour Egypt :: Egypt: A Carefree Childhood in Ancient Egypt". Retrieved 15 August 2016.
  21. ^Shuter, Jane (2003). The Egyptians. Raintree. p. 10. ISBN .
  22. ^Fontanel, Béatrice; D'Harcourt, Claire (1997). Babies: history, art, and folklore. Harry N. Abrams. p. 64. ISBN .
  23. ^Colón, A. R.; Colón, P. A. (1999). Nurturing Children: A History of Pediatrics. Greenwood Press. p. 20. ISBN .
  24. ^Blum, Richard H.; Blum, Eva Marie (1970). The Dangerous Hour: The Lore of Crisis and Mystery in Rural Greece. Scribner. p. 336.
  25. ^Food – Frozen mice & ratsArchived 10 October 2009 at the Wayback Machine, Canberra Exotic Pets / reptilesinc.com.au, accessed 14 November 2009
  26. ^"South Florida's True Rodent Professionals". Archived from the original on 30 January 2009. Retrieved 29 May 2009.

External links

Wikimedia Commons has media related to Mice.
Sours: https://en.wikipedia.org/wiki/Mouse


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