The fancy rat is a domesticated brown rat (Rattus norvegicus), which is the most common type of pet rat. The name fancy rat derives from the idea of animal fancy or the phrase "to fancy" (to like, or appreciate).
Fancy rats have their origins as the targets for blood sport in 18th and 19th century Europe. Specially bred as pets since then, fancy rats now come in a wide variety of colours and coat types and there exists several rat fancy groups worldwide. Fancy rats are commonly sold as pets in stores and by breeders. In fiction, pet brown rats are often depicted as tamed rather than domesticated, akin to when a character befriends a wolf. As tamed pets, they have been portrayed in roles that vary from evil to ambiguous to lovable.
Domesticated rats are physiologically and psychologically different from their wild relatives, and, when acquired from reliable sources (such as a breeder), they pose no more of a health risk than other common pets. For example, domesticated brown rats are not considered a plague threat, though exposure to wild rat populations could introduce pathogens like Salmonella into the home. Fancy rats experience different health risks from their wild counterparts, and as such, are less likely to succumb to the same illnesses as wild rats.
The origin of the modern fancy rat begins with the rat-catchers of the 18th and 19th centuries who trapped rats throughout Europe. These rat-catchers would then either kill the rats, or, more likely, sell the rats to be used in bloodsport. Rat-baiting was a popular sport until the beginning of the 20th century. It involved filling a pit with several rats and then placing bets on how long it would take a terrier to kill them all. It is believed that both rat-catchers and sportsmen began to keep certain, odd-colored rats during the height of the sport, eventually breeding them and then selling them as pets. The two men thought to have formed the basis of rat fancy are Jack Black, rat-catcher to Queen Victoria, and Jimmy Shaw, manager of one of the largest sporting public houses in London. These two men are responsible for beginning many of the color varieties present today. Black, specifically, was known for taming the “prettier” rats of unusual color, decorating them with ribbons, and selling them as pets. It was not uncommon in upper circles of Victorian England to see a lady with her pet rat on a short monkey leash sitting on her lap, grandly festooned with ribbons.
Rat fancy as a formal, organized hobby began when a woman named Mary Douglas asked for permission to bring her pet rats to an exhibition of the National Mouse Club at the Aylesbury Town Show in England on October 24, 1901. Her black-and-white hooded rat won "Best in Show" and ignited interest in the area. After Douglas' death in 1921, rat fancy soon began to fall back out of fashion. The original hobby formally lasted from 1912 to 1929 or 1931, as part of the National Mouse and Rat Club, at which point Rat was dropped from the name, returning it to the original National Mouse Club. The hobby was revived in 1976 with the formation of the English National Fancy Rat Society (NFRS). Pet rats are now commonly available in stores and from breeders, and there exist several rat fancy groups worldwide.
Differences from wild rats 
While domesticated rats are not removed enough from their wild counterparts to justify a distinct subspecies (compare Canis lupus familiaris), there are significant differences that set them apart; the most apparent is coloring. Random color mutations may occur in the wild, but these are rare. Most wild R. norvegicus are a dark brown color, and fancy rats may be anything from white to cinnamon to blue.
Behaviorally, domesticated pet rats are tamer than those in the wild. They are more comfortable around humans, known to seek out their owners while roaming freely. They have decreased reactions to light and sound, are less wary of new foods, and have better tolerance to overcrowding. Fancy rats are shown to mate earlier, more readily, and for a longer period of time over their lifespan. Also, domesticated rats exhibit different behaviors when fighting with each other; while wild rats almost always flee a lost battle, caged rats spend protracted amounts of time in a belly-up or boxing position. These behavioral traits are thought to be products of environment as opposed to genetics. However, it is also accepted that there are certain underlying biological reasons for why some members of a wild species are more receptive to domestication than others, and that these differences are then passed down to offspring (compare Domesticated silver fox).
Domesticated rats have a longer lifespan than that of wild rats. Because domesticated rats are protected from predators and have ready access to food, water, shelter, and medical care, their average lifespan is around 2 years, in contrast to wild R. norvegicus which average a lifespan of less than one year. However, wild rats generally have larger brains, hearts, livers, kidneys, and adrenal glands than laboratory rats. The fancy rat and wild rat also both face a multitude of differing health concerns; the former is at risk of developing a pneumococcal infection from exposure to humans, while the latter may harbor tapeworms after coming in contact with carriers like cockroaches and fleas.
Social behavior 
Particularly with males, there can be some fighting in the beginning, but once an alpha rat has been determined, the rats should get along well. Within a week or two, the rats will most likely have adjusted and become friendlier with each other. Rats are generally very friendly to other cage mates, particularly with females. They will even sometimes help or take care of other sick rats.
Fancy Rats as Pets 
As pets, fancy rats are the most intelligent, affectionate and responsive of all the small rodents. They are great as pets for children and are extremely social. In fact, fancy rats do better in same sex pairs than on their own, and because of that, it is recommended that you invest in at least two rats, rather than one. Opposite sex rats will mate and leave the owner with many kittens.
Though they are quite social, fancy rats usually don’t do well with other pets such as cats or dogs, though there are definitely some exceptions. They enjoy exploring new environments and chewing, so the owner must make sure areas are “rat-proof” before letting their pet roam.
Fancy rats’ lifespan is usually about 2 years, but they are prone to respiratory infections that can cause health problems throughout their lives. Fancy rats can also develop scabs, abscesses, tumors and deformed teeth. A few veterinary visits may be required and owners should watch out for strange behavior or any other signs of health issues.
Besides potential veterinary costs, rat care and maintenance costs should not be too high. A large cage, bedding, rat food and chew toys are the only requirements. 
As in other pet species, a variety of colors, coat types, and other features that do not appear in the wild have either been developed, or have appeared spontaneously. Any individual rat may be defined one or more ways by its color, coat, marking, and non-standard body type. This allows for very specific classifications such as a ruby-eyed cinnamon berkshire rex dumbo.
While some pet rats retain the "agouti" coloring of the wild brown rat (three tones on the same hair), others may be black-based colors (a single color on each hair). Agouti-based colors include agouti, cinnamon, and fawn. Black-based colors include black, beige, and chocolate. Additionally, eye color is considered a subset of coloring, and coat color definitions often include standards for the eyes as many genes which control eye color will also affect the coat color. The American Fancy Rat and Mouse Association (AFRMA) lists black, pink, ruby, and odd-eyed (two different colored eyes) as possible eye colors depending on the variety of rat shown. Ruby refers to eyes which at a glance appear black but which are on closer observation a deep, dark red. Color names can vary for more vague varieties, like lilac and fawn, while the interpretations of standards can fluctuate between (and even within) different countries or clubs.
Further dividing the varieties of fancy rats are the many different markings. Pet rats can appear in any combination of color and marking. The markings are typically in reference to the patterns and ratios of colored hair versus white hair. Two extremes would be a self (completely solid, non-white color) and a Himalayan (completely white with a gradual blend of coloring toward its nose and feet, called "points", as in a Siamese cat's markings).
Markings have a strict standard for showing in fancy pet rat shows. For example, in the case of hooded rats, the stripe or "saddle" should be a single, unbroken line that runs down the spine and possibly partly down the tail. However, many domestic rats are not bred to a colour standard such as those found in pet shops, and as such, will have "mismarkings", which are defined as variations in markings that are not recognized as "standard" by rat fancy clubs.
Commonly recognized standards include:
- Berkshire – coloured top, white belly
- Hooded – colour runs 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 run down the back only
- Irish or English Irish – In England the Irish is standardized by the NFRS as an equilateral triangle of white with a side that begins at the chest, or between the front legs, and where the point ends mid length. In the United States and elsewhere, clubs like the AFRMA distinguish this marking as the English Irish and allow for another standard Irish in which the rat may have white of an even or symmetrical nature anywhere along its underside.
Other marking varieties include Dalmatian-like spotting, blazes, masks, and Siamese (typically a gradient of colour along the body, darkest at the base of the tail and nose as in Siamese cats), and "downunders" (an Australian variety which has a solid colour stripe on the belly or a colour marking that corresponds to markings on top).
Body types 
Two of the most prominent (and thus standardized) physical changes applied to rats through selective breeding are the development of the Manx and Dumbo. The Dumbo, whose origins are in the United States, is characterized by having large, low, round ears on the sides of its head, while the Manx rat shares both its name and mutation with tailless Manx cats.
Coat types 
There is a relatively small variety of coats in relation to the number of colours and markings, and not all are internationally standardized. The most common type is the Normal or "Standard," which is allowed variance in coarseness between the sexes; males have a coarse, thick, rough coat, while females' coats are softer and finer. Other standardized coats include: Rex, in which all the hairs are curly, even the whiskers; Velveteen, a softer variation on the Rex; Satin or Silky coats, which are extra soft and fine with a sheen; and Harley, characterized by whispy long straight hairs. Remaining coat types are not defined by the hair itself, but rather by the lack of it, such as hairless rats.
Hairless rats 
Hairless rats are a coat variety characterized by varying levels of hair loss. Hairless rats, bred from curly-coated Rexes, range from having areas of very short fur to being completely bare. Hairless rats are genetically produced by breeding different combinations of the genes that cause Rex coats. Since Rex is a dominant trait, there only needs to be one Rex parent to produce curly Rex-coated offspring. However, when two copies of the trait are present, by breeding two Rexes together, the coat is affected differently—causing hairlessness, and earning the colloquial name, "Double-rex". One subset of semi-hairless rats, Patchwork rats, constantly lose hair and regrow it in different "patches" several times throughout their life.
Ethics of selective breeding 
There is controversy among rat fanciers in regard to selective breeding. On one hand, breeding rats to "conform" to a specific standard or to develop a new one is a large part of what the fancy was founded on. On the other hand, the process results in many rats who do not "conform", and are then either given away, sold as food, or killed—referred to as culling. Additionally, there are concerns as to whether or not breeding hairless and tailless rats is ethical. The tail is vital for rats' balance and for adjusting body temperature. Tailless rats have greater risk of heat exhaustion, poor bowel and bladder control, falling from heights, and can be at risk for life-threatening deformities in the pelvic region like hind leg paralysis and megacolon. Similarly, hairless rats are less protected from scratches and the cold without their coat. Groups such as the NFRS prohibit the showing of these varieties at their events and forbid advertisement through affiliated services.
Because R. norvegicus and related species are seen as pests, their intentional import into foreign countries is often regulated. For example, the importation of foreign rodents is prohibited in Australia, and so various coat types, colours, and varieties have been bred separately from foreign lines, or are just not obtainable within that country. In other areas, like the Canadian province of Alberta, which is considered rat-free, the ownership of domestic fancy rats outside of schools, laboratories, and zoos is illegal.
Human-raised R. norvegicus are more prone to specific health risks and diseases than their wild counterparts, but 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 usually are able to avoid disease-causing bacteria such as Salmonella and Pseudomonas aeruginosa; the latter is absent in treated water. They may also more easily avoid vectors like cockroaches, beetles, and fleas who are essential for the spread of endemic typhus and intestinal parasites like the Rat tapeworm. Additionally, pet or laboratory rats enjoy the intrinsic benefits of having a consistent and well-balanced diet, along with access to medical care.
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 inherently associated with living in an unnatural habitat can all adversely affect a rat's health to make them more 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, not the same bacteria associated with strep throat. A human-associated fungus, Pneumocystis carinii (also found in almost all domesticated animals) is usually asymptomatic in the rat, unless the rat's immune system is compromised by illness. If this occurs the infection can develop into pneumonia.
Several diseases, like Rat Coronavirus Infection (RCI), Sendai virus, and Murine Respiratory Mycoplasmosis (MRM, Mycoplasma pulmonis), are 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 in those kept as pets.
Pet rats can also develop pituitary tumors if they are given high-calorie diets, and ringtail if they are placed in areas with low humidity, high temperatures, or drafts. Staphylococcus spp. are a mostly benign group of bacteria that commonly reside on the top of the skin, but cuts and scratches from social and hierarchal fighting can open up the pathways for them to cause ulcerative dermatitis.
Risks to owners 
Keeping rats as pets can come with the stigma that rats supposedly transmit dangerous diseases to their owners. One fear is that all rats carry plague, when in fact R. norvegicus is not among the list of species considered a threat. In 2004, an outbreak of salmonella in the United States was connected to people who owned pet rats, however it has been determined that a pet rat's initial exposure to salmonella, along with many other zoonotic rat-diseases, typically indicates exposure to wild rodent populations, either from an infestation in the owner's home, or from the pet's contaminated food, water, or bedding. Pet rats otherwise pose little threat for zoonotic disease especially compared to other pets which go outside frequently or typically socialize with many other members of their species.
Samantha Martin, a professional animal trainer for films, commercials, and music videos, has claimed that rats are one of the easiest animals to train due to their adaptability, intelligence, and focus. Rather than portraying pet brown rats as thoroughly domesticated, they are often cast as a wild brown rat which a character tames.
The short novel Ratman's Notebooks by Stephen Gilbert was the basis for the films Willard, Ben, and a 2003 remake of the first film. Here, the protagonist befriends the rats found in his home and builds up a close relationship, only to have it end tragically. While these movies generally emphasize the popular perception of malevolence—they kill people, cats, and ransack grocery stores—other wild rats who become pets are portrayed in more neutral to positive ways; the television show, House, shortly featured "Steve McQueen", the pet rat of the titular character, and the 2007 film, Ratatouille, is about a rat described by Roger Ebert as "earnest... lovable, determined, [and] gifted" who lives with a Parisian garbage boy.
In many versions of the Teenage Mutant Ninja Turtles franchise, the master and adoptive father of the turtles is Splinter, who was once the pet rat of ninja Hamato Yoshi and learned his martial arts skills by imitating his owner.
See also 
- American Fancy Rat and Mouse Association, US
- Fancy mouse
- Experimental evolution
- List of fictional mice and rats
- National Fancy Rat Society, UK
- Rat agility
- Rat genome database
- Working rat
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|Wikimedia Commons has media related to: Pet rats|
- RodentFancy.com – A site maintained by the former head of the defunct Rat & Mouse Fanciers for Excellence (RMFE).
- Rat Behavior and Biology – A website with useful referenced articles that pertain to the scientific study of the domesticated Norway Rat.
- Rat Guide - An online resource with information about fancy rat health and treatment of illness