The fancy rat or pet rat is a domesticated breed of the brown rat (Rattus norvegicus). The name fancy rat has nothing to do with the "fanciness" of their appearance, but derives from the phrase animal fancy. Thus, one who keeps pet rats is said to be involved in "rat fancy." There are some rat fanciers who domesticate black rats (Rattus rattus), and Gambian pouched rats (Cricetomys gambianus), but these are not generally referred to as fancy rats as the hobby does not formally center around them.

Specially bred as pets at least since the late 19th century, fancy rats come in a wide variety of colors and coat types. They are sociable, intelligent animals that can be trained to come when called, use a litter box, and perform a variety of tricks. Pet rats behave differently from their wild relatives depending on how many generations they have been removed, and, when acquired from reliable sources, they do not pose any more of a health risk than other common pets.

Pet rats in fiction have played roles varying from evil, to ambiguous, to lovable. The theme of a human taking in a wild rat is highly prevalent, while the depiction of true rat fancy is virtually non-existent within mainstream media.

History

The bloody sport of rat-baiting is an unlikely foundation for the practice of keeping rats 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 colour varieties present today.^[2]

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 on October 24, 1901. Her black and white hooded rat won "Best in Show," igniting interest in the area. The original hobby lasted until 1931, as part of the National Mouse and Rat Club, and was then revived in 1976 with the formation of the National Fancy Rat Society (NFRS).^[2] There presently exist several rat fancy groups worldwide and rats are commonly sold as pets in stores and by breeders.

Differences from wild rats

While domesticated rats are not so far removed from their wild counterparts as to justify a distinct subspecies (compare Canis lupus familiaris), there are several significant differences that set them apart. The most apparent of which is colouring. While random colour mutations may occur in the wild, these are rare. While most wild R. norvegicus are a dark brown colour, fancy rats may be anything from white to blue.

Behaviourally, pet rats are generally more tame than those in the wild. They are more comfortable around humans, have decreased reactions to light and sound, are less wary of new foods, and can better tolerate overcrowding. They have been shown to mate earlier, more readily, and for a longer period of time over their lifespan.^[4] Also, domesticated rats exhibit different behaviours 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.^[5] All of these behavioural 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.^[4][5]

At a physiological level, while still the same species, domesticated rats have different average statistics than wild rats. The chief difference is lifespan. Because domesticated rats are protected from predators, have ready access to food, water, shelter, and medical care, their average lifespan is around 2-3 years. Contrast that to the high mortality rate of wild R. norvegicus, with a lifespan of less than one year.^[6] Wild rats also generally have larger brains, hearts, livers, kidneys, and adrenal glands.^[4] 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.

Varieties

The American Blue is just one of several standardized coat colours.

Colouring

While some pet rats retain the "agouti" (three tones on the same hair) colouring of the wild brown rat, others may be black based colours (a single colour on each hair). Agouti based colours include: agouti, amber, cinnamon, blue agouti, and fawn. Black based colours include black, blue, chocolate, mink, pearl, silver, and white.

Colour definitions tend to vary for more vague varieties, like fawn for champagne or mink for cinnamon. They can fluctuate between and even within different countries or clubs.^[7][8]

Additionally, eye-colour is considered a subset of colouring, many coat-colour definitions including standards for the eyes. They may be black, pink, ruby, or odd-eyed (two different types).^[7][8] Pink and ruby eyes are controlled by a gene that dilutes the normal black colour of the eyes, but it also affects the coat. Ruby eyed rats have eyes that normally appear black, yet appear red while in the light.

Markings

Further dividing the varieties of fancy rats are the many different markings. Pet rats can appear in any combination of colour and marking. The markings are typically in reference to the patterns and ratios of coloured hair versus white hair. The two extremes would be a self (completely solid, non-white colour) and a Himalayan (completely white with a gradual blend of sepia colouring toward its nose and feet).

Himalayan rats have a unique colour and marking variation.

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 the UK 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 underside.

Other marking varieties include Dalmatian-like spotting, blazes, masks (only around the eyes), Siamese (typically a gradient of colour along the body, being darkest at the base of the tail), and "downunders" (an Australian variety having a solid colour stripe on the belly or a colour marking that corresponds to those on top).

Coat types

There is a relatively small variety of coats, 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.

Well-known 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; Harley, characterized by long straight hairs. Remaining coat types are not defined by the hair itself, but rather by the lack of it.

Hairless rats

There are certain rats that have little or no hair at all.

Hairless, or Sphinx rats are a coat variety characterized by their complete lack of hair except for the whiskers and perhaps a non-standard small patch near the top of their head. Semi-hairless rats, bred from Rexes, have varying areas of bare skin, or very short fur on their bodies. Because the Rex coat is a dominant trait, it only needs one Rex-parent to affect the rat's appearance. However, when two copies of the trait appear, by breeding two Rexes together, the coat is affected differently?causing semi-hairlessness, and earning the colloquial name, "Double-rex". Semi-hairless varieties are produced by different combinations of the various genes that cause Rex coats. One subset of semi-hairless rats, patchwork rats, constantly lose hair and regrow it in different "patches" several times throughout their lifetimes.^[7][8][9]

Physical changes

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.^[7] Manx rats borrow their name from the tailless cats on the Isle of Man. Manx rat tails also come in the same stumpy, rumpy, and rumpy-riser varieties as those of Manx cats.

A male "Dumbo" rat, a variety with ears placed lower on the head. Named for resemblance to Dumbo the elephant.

Ethics of selective breeding

There is controversy among rat fanciers regarding selective breeding.^[10][11] On one hand, breeding rats to conform to a specific standard or to develop a new one is a large part of what the hobby 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.^[12] 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.^[13] Similarly, hairless rats are less protected from scratches and the cold without their coat. Some groups, like the NFRS, prohibit the showing of these varieties at their events and forbid advertisement through affiliated services.^[14]

Accessibility

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 had to been bred separately from foreign lines, or are just not obtainable within that country. In other areas, like the Canadian province of Alberta, the ownership of Brown rats outside of schools, laboratories, and zoos is illegal.^[15]

Health

Fancy rats commonly develop mammary tumors in their old age. These are usually benign but multiple tumors can persist even after removal.

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. Finally, rats that are in the care of humans have access to surgery for the benign mammary tumors that are common to both sexes.^[16]

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, 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 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. In cages, however, stressors can increase aggressiveness between rats, causing more frequent and intense fighting.^[16]

Risks to owners

Keeping rats as pets occasionally comes with some stigma that the rats could potentially transmit a dangerous disease to their owners. A common fear is that all rats carry plague, when in fact R. norvegicus is not among the list of species considered a threat.^[17] Owners of domesticated rats should be aware of the potential exposure to diseases like salmonella, responsible for a 2004 outbreak.^[18] A pet rat's 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.^[16]

In entertainment

Due to their intelligent nature and trainability, rats have appeared in several majour film releases and television series throughout the world.^[19] They also occasionally appear as central or important characters in novels, comics, and video games. Rats may appear as domesticated pets, wild vermin, or as anything else between the two. The portrayal of fancy rats in entertainment is extremely limited, pet rats are usually only seen as tamed brown rats or former lab rats. Often, a pet rat is cast as a wild rat that a character has taken in, like a human befriending a wolf. An example of this is in the series of movies based on Ratman's Notebooks: 1971's Willard, the sequel Ben, and 2003's Willard. These movies entail the protagonist befriending the rats found in his home and building up a close relationship, only to have the friendship end in tragedy. 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, like in the television shows Fawlty Towers and House. Films in this same trend include Ratatouille, with a rat described by Roger Ebert as, "earnest... lovable, determined, [and] gifted....^[20]" Moving in the opposite direction, a transition from pet rat to wild rat, is the movie Flushed Away - about a rat living in lonely luxury, who in the end chooses to leave that life for one amongst his newfound sewer-dwelling companions. Then there are pet rats in media whose background origins are irrelevant to the story. The well-known mutant rat Splinter was kept as a pet by an experienced martial artist in one origin story, and learned his skills mimicking them from his cage before the mutation. In novels, pet rats tend to play the role of minor or secondary characters, often belonging to one of the main protagonists, such as in Stargirl and the Harry Potter series. The secondary role to central characters is continued in several video games like Phantasmagoria 2: A Puzzle of Flesh and Comix Zone. In others, notably World of Warcraft, rats can be chosen to be kept as pets by the player.

References

See also

• Rat agility
• Rat genome database
• Experimental evolution
• National Fancy Rat Society, UK
• American Fancy Rat and Mouse Association, US
• List of fictional mice and rats

External links

• "Biology of the Rat." Louisiana Veterinary Medical Association, 2000.
• Rats as Pets

Organizations

• American Fancy Rat and Mouse Association (AFRMA)
• The National Fancy Rat Society (UK) (NFRS)
• Rat & Mouse Club of America (RMCA)

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