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Fancy rat Fossil range: Early Pleistocene - Recent
A pet rat eating a slice of watermelon
Conservation status
Domesticated
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Suborder: Myomorpha Superfamily: Muroidea Family: Muridae Subfamily: Murinae Genus: Rattus Fischer de Waldheim, 1803
Species
R. rattus R. norvegicus

The fancy rat or pet rat is a domesticated breed of the Brown Rat (Rattus norvegicus) or, more rarely, of the Black Rat (R. rattus). The name "fancy rat" has nothing to do with the "fanciness" of their appearance but derives from the meaning of "to fancy". Thus, one who keeps pet rats is said to be involved in "rat fancy."

A domesticated rat, often happy to stay on its owner's shoulder.

Specially bred as pets at least since the late 19th century, the rats are sociable, intelligent animals and can be trained to use a litter box, come when called, and perform a variety of tricks. Pet rats are typically of variants of the species R. Norvegicus, or Brown rat, but Black rats and Giant pouched rats are also known to be kept. Pet rats behave differently than their wild relatives depending on how many generations they have been removed, and when acquired from reliable sources, they do not pose any more health risk than other, more common pets.

Pet rats live about 2 to 3 1/2 years though the oldest rat on record - a lab rat called Rodney - reached a purported age of 7 years and 4 months, according to the 1995 Guinness Book of Records. Bucks (male rats) reach an average weight of between 400 g and 800 g, while does (female rats) can average between 250 g and 450 g. Female rats tend to be more active than male rats.

A Pink-Eyed-White(Albino) pet rat.

The origin of the modern fancy rat is probably the rat-catchers of the late 19th century who trapped rats and were paid by town governments per rat, and who also kept certain rats for exhibition/gambling fights. They began breeding rats and became attached to some as they discovered how intelligent and trainable rats can be. One of the most famous of these rat catchers was Jack Black, ratcatcher to Queen Victoria, who became known for breeding and selling pet rats around 1840-1860. Rats became more and more domesticated and people enjoyed them since they are easily bred, social and intelligent^[1] pets. The first rat show was held in 1901 in England. Beatrix Potter, author of the "Peter Rabbit" series of children's books, had a white pet rat of which she was very fond, and in remembrance of which she dedicated the story "The Roly-Poly Pudding".

Rat fancy as a formal organised hobby did not begin until Mary Douglas asked for permission from the National Mouse Club to bring her pet rats to an exhibition at the Aylesbury Town Show on October 24, 1901. Her black and white hooded Rattus norvegicus won "Best in Show," and the Rat Fancy was formally launched.

The original Rat Fancy lasted until 1931, as part of the National Mouse and Rat Club. The modern Rat Fancy was revived in 1976 with the formation of the National Fancy Rat Society, and the fancy spread around the world.

Ratkeeping grew in popularity in the 1970s, leading to the formation of the British National Fancy Rat Society in 1976. There presently exist several rat fancy groups worldwide and pet rats are commonly sold in stores and by breeders.

American Blue rat.

As in other pet species, a variety of colours, coat types, and other features that do not appear in the wild have been either developed or arisen spontaneously in pet rats.

While some pet rats retain the "agouti" (three tones on the same hair) colouring of the wild brown rat, other colours may include blue, chocolate, silver, black, white, and pearl, fawn/champagne/beige, and mink/cinnamon. Colour definitions tend to vary for more vague varieties like fawn and champagne, or mink and cinnamon. They can fluctuate between and even within different countries or clubs.^[2][3]

A black hooded rat. Note the uneven splotchy effect of the "saddle" down its spine. This would be considered a poorly standardized hooded.

In addition to the many colours, there are also many different markings. The markings are typically in reference to the patterns and ratios of coloured hair versus white hair. The two extremes would be a Self and a Himalayan (as defined by the NFRS). The former being completely coloured while the latter only has a gradual blend of colouring towards its nose. Markings usually have a strict standard, for example in the case of hooded rats - the stripe, or "saddle" should be a single, unbroken line running down the spine and possibly partly down the tail. However, many rats are not bred strictly to the standard (such as those found in pet shops), and will have "mismarkings."

Internationally recognized standards include:

• Berkshire - coloured top, white belly
• Hooded - colour running from full head down spine
• Capped - colour on full head only
• Variegated - a blaze, or short white strip on the forehead, with a fully coloured head and splotches or flecks of colour running down the back only
• Essex - similar to Berkshire, only that the colour fades to white rather than ending abruptly
• Bareback - colour fully on head, neck, and chest only (not officially standardized in the UK)
• Irish or English Irish - In England this marking is only standardized as an equilateral triangle of white with a side beginning at the chest, or between the front legs, and the point ending mid length. The AFRMA, another international rat fancier club, distinguishes this marking as the English Irish and allows for another standard Irish in which the rat may have white of an even or symmetrical nature anywhere along its belly.

Siamese rats are a unique colour and marking variation, the result of concentrated efforts by breeders.

Other marking varieties include Dalmatian-like spotting, blazes, masks (only around the eyes), Siamese (typically a gradient of colour on the nose), and "downunders" (an Australian variety which have markings on the belly that correspond to those on top). Additionally, eye-colour is considered a subset of colouring, many coat-colour definitions including standards for the eyes. They may be black, ruby, pink, or odd-eyed (one of each).^[2][3]

A hairless rat.

There is a relatively small variety of coats, and not all are internationally standardized as such. The most common type is the Normal or "Standard," which is allowed variance in coarseness between sexes; the males have a coarse, thick, rough coat, while the females' coats are softer and finer. One of the more exotic coats includes the Rex coat; all the hairs are curly, even the whiskers. Satin or silky coats are extra soft, fine, and have a sheen. The remaining coat types are not defined by the hair itself, but rather by the lack of it.

Hairless, or Sphynx, rats are a coat variety characterized by their completely bare skin except perhaps near the top of their heads (not standard) and their whiskers. Semi-hairless rats, sometimes called double-rex rats, have varying areas of bare skin or very short fur on their bodies. One subset of semi-hairless rats, patchwork rats, constantly lose hair and regrow it in different "patches" several times throughout their lifetimes. Semi-hairless rats are not related to true hairless rats, are are produced by different combinations of the various genes that cause rex, or curly, coats.^[2][3][4]

In laboratory rats there are currently three known genes that can cause recessive hairlessness. They are denoted as rnu (Rowett nude), fz (fuzzy), and shn (shorn). When an organism is identified as having a visible recessive trait, the gene pair (from the father and mother) is listed like such: rnu/rnu. All three gene types have characteristic health problems. The hairless rats kept as pets do not seem to be related to the hairless lab rats and do not have any unusual health problems.^[5]

Rowett nudes, first identified in 1953 in Scotland, have no thymus. The lack of this organ severely compromises their immune system, infections of the respiratory tract and eye increasing the most dramatically. Their average life span is about nine months.^[5].

A fancy rat with a large mammary tumor.

Fancy rats being defined as a purely domesticated subset of either R. rattus or, more typically, R. norvegicus, are more prone to specific health concerns and diseases than their wild counterparts. Conversely they are also far less likely to succumb to certain illnesses that are prevalent in the wild. The major considerations for susceptibility include exposure, living conditions, and diet.

Rats that live their entire lives indoors are able to avoid disease-causing bacteria such as Salmonella and Pseudomonas aeruginosa, the latter being absent in treated water. They may also more easily avoid vectors like cockroaches, beetles, and fleas who are essential for the spread of Bubonic plague and intestinal cestodes like the Rat tapeworm. Additionally, pet or laboratory rats enjoy the natural benefits of having a consistent and well-balanced diet. However, this could be countered with the fact that outside of the laboratory rats may not always be receiving proper nutrition. Lab blocks are excellent source of nutrition for rats. Finally, rats that are in the care of humans have access to surgery for the benign mammary tumors that are common to both sexes.^[6]

This is a Zucker Rat, a pet rat that has developed diabetes as a result of a genetic disorder that causes obesity.

While living indoors decreases the risk of contracting certain diseases, living in close quarters with other rats, being unable to always seek proper protection from environmental factors (e.g. temperature, humidity, drafts), being fed an unhealthy diet, and the stresses naturally associated with living in an unnatural habitat can all have adverse effects on a rat's health making them prone to specific conditions. Specifically, Tyzzer's disease, Protozoic infections (e.g. Giardia muris), and Pseudotuberculosis are usually seen in stressed or young rats. Additionally, pet rats are exposed to Streptococcus pneumoniae, a zoonotic disease caught from humans. Another bacteria associated with humans, Pneumocystis carinii, is actually found in almost all domesticated animals. However it is asymptomatic unless the rat's immune system is compromised by illness, then it can develop into pneumonia. Several diseases, like Rat Coronavirus Infection (RCI), Sendai virus, and Murine Respiratory Mycoplasmosis (MRM, Mycoplasma pulmonis), are more prevalent simply because their highly contagious natures work in tandem with the way rats are kept in laboratories, pet stores, and by breeders. It should be noted, however, that MRM is far less likely to occur in laboratory rats than those kept as pets. Pet rats can also develop pituitary tumors if they are given high-calorie diets or come down with ringtail if placed in areas with low humidty, high temperatures, or drafts. Staphylococcus spp are a mostly benign group of bacteria that commonly reside on the top of the skin. Cuts and scratches can open up the pathways for them to cause ulcerative dermatitis. Cuts and scratches are a normal part of every rat's life, they are social animals who periodically spar for positions within their loose hierarchy. However when being caged, stressors can increase aggressiveness between rats, causing more frequent and intense fighting.^[6]

Since Muybridge's first films, rats have been widely used in entertainment media. Due to their intelligent nature and trainability, rats have appeared in over 413^{[citation needed]} major film releases throughout the world, and in at least seventy-one television series. For example, Scabbers is a rat-animal in the Harry Potter book/film series. In The Curious Incident of the Dog in the Night-time, Christopher Boone, the autistic protagonist, keeps a pet rat named Toby. In the Buffy the Vampire Slayer TV series, the character of Amy is turned into a rat and is kept as a pet by Willow for several seasons before she is changed back into a human.

The 2006 Dreamworks and Aardman film, Flushed Away, stars Roddy St. James, a pet mouse who gets flushed down a toilet and into a city in the London sewers populated by rats.

In 2007, Disney/Pixar released one of the few movies to actually feature a rat as the main character - "Ratatouille" stars a rat named Remy who wants to be a Parisian chef.

In the book series Babysitter's Little Sister, Karen Brewer, the main character, receives a pet rat after her pet fish dies. She names him Nicodemus, after the character from Mrs. Frisby and the Rats of Nimh.

The computer game Phantasmagoria 2: A Puzzle of Flesh features a main character who has a beloved pet rat named Blob. Blob is actually instrumental in a beginning puzzle, where she retrieves the character's wallet (although it's revealed she's the reason it went missing to begin with).

In the Sega Game Comix Zone, the main character, Sketch Turner, has a pet rat, RoadKill, whom he rescued from the street, becoming his sidekick.

On House the titular character, Gregory House, adopts a rat he finds in his ex-girlfriend's house, after treating it for mycoplasmosis. He christens the rat Steve McQueen, after the actor of whom House is a fan.

In the British comedy series Fawlty Towers, the waiter Manuel keeps a pet rat named Basil, named after the hotel owner Basil Fawlty. Manuel, who insisted the rat was a hamster has to keep it a secret from Basil or he will be fired.

In the children's novel Stargirl , by Jerry Spinelli, the main character, Stargirl Caraway, has a pet rat named Cinnamon, who stays in her bag during school hours.

In the movie The Abyss Alan 'Hippy' Carnes has a pet rat named Beany who is used to demonstrate that mammals can breathe an oxygenated fluorocarbon emulsion. In one scene Hippy puts Beany in a plastic bag to ensure that she doesn't drown while the ship fills with water.

Rats in films are often depicted as squeaking, usually for dramatic effect. However rats do not usually squeak, normal vocalizations being too high-pitched for human ears; they only may do so if distressed or annoyed.

Rats are often in roles that emphasize the popular perception of them as malevolent vermin. The 1971 film Willard is a notable example; it features a horde of rats trained to exact revenge on behalf of a social misfit, but also shows some realistic social interactions among the rats. An alpha rat named Big Ben(played by a giant pouch rat) becomes jealous of the attention a smart rat named Socrates is getting, and tries to murder his rival.

In The Secret of NIMH, genetically enhanced lab rats are portrayed as nearly human.

The short story Three Skeleton Key, written by George Toudouze, features three lighthouse keepers who are trapped in their lighthouse by an army of starving rats coming off a derelict ship.

Brown Rat (Rattus norvegicus)

It was discovered that rats emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, and when tickled. The vocalization is described as a distinct "chirping." Humans cannot hear the "chirping" without special equipment. It was also discovered that, like humans, rats have "tickle skin": certain areas of the body that generate more laughter response than other areas. The laughter is associated with positive emotional feelings, and social bonding occurs with the human tickler, resulting in the rats becoming conditioned to seek the tickling. Additional responses to the tickling included: those that laughed the most also played the most, and those that laughed the most preferred to spend more time with other laughing rats. This suggests a social preference to other rats exhibiting similar responses. However, as the rats age, there does appear to be a decline in the tendency to laugh and in the response to tickle skin. The initial goal of Jaak Panksepp & Jeff Burgdorf’s research was to track the biological origins of joyful and social processes of the brain by comparing rats and their relationship to the joy and laughter commonly experienced by children in social play. Although, the research was unable to prove rats have a sense of humor, it did indicate rats can laugh and express joy. Panksepp & Burgdorf 2003 Chirping by rats is also reported in additional studies by Brian Knutson of the National Institutes of Health. Rats chirp when wrestling one another, and before receiving morphine or having sex. The sound has been interpreted as an expectation of something rewarding. Science News 2001

• Rat
• Black rat
• Brown Rat
• List of fictional mice and rats
• Rat-baiting
• Rat genome database
• National Fancy Rat Society
• American Fancy Rat and Mouse Association
• Rat agility

• The National Fancy Rat Society (UK)
• American Fancy Rat and Mouse Association
• "Biology of the Rat." Louisiana Veterinary Medical Association, 2000.