Fancy Rat and Mouse Day and the Rat Bred to Be Handled

A pet rat is a Norway rat, Rattus norvegicus, the same species that lives in sewers, on docks and under subway platforms. It is also the product of more than a century of people choosing which rats to breed, and much of that choosing came down to whether the animal was comfortable in human hands.

Fancy Rat and Mouse Day, November 12th, is about that animal and the hobby that shaped it.

The Club Behind the Date

The day belongs to the American Fancy Rat and Mouse Association, which calls it the official AFRMA Fancy Rat & Mouse Day, a day for fancy rats and mice, the people who breed them and the hobby itself. The date is fixed, so in 2026 it falls on a Thursday, and the club was already marking it by 2014. AFRMA is a fanciers' club that runs shows for rats and mice and promotes breeding them to a standard.

A Show Bench in Aylesbury, 1901

"Fancy" is the old word for breeding animals to a standard. On October 24, 1901, at the Aylesbury Fanciers' show in England, Mary Douglas persuaded the organizers to put on classes for rats. Fifteen were entered in one class. Douglas won it with a black and white rat of the pattern now called hooded, and she became known as the mother of the rat fancy. She stayed the hobby's driving force until her death in 1921, after which it faded. Britain did not get a rats-only club until the National Fancy Rat Society formed in 1976.

She did it through the National Mouse Club, founded in 1895, so the mouse fancy is the older of the two. The judge at Aylesbury was Walter Maxey, remembered as the father of the mouse fancy. Rats appeared at least twice more on show benches that year, and by 1912 the club had added rats to its name.

The mouse shared those show halls and is a different animal to live with. It is smaller, faster and quicker to startle, so a mouse is lifted in cupped hands, never by the tail tip.

The rats on those benches came out of a grim trade. Nineteenth-century rat catchers supplied wild rats in bulk to the rat pits, a blood sport where a terrier was set on as many as 100 at a time, and oddly colored rats turned up in the catch. Those were kept and bred. Rats had been kept as pets in Japan from at least the 18th century, but the Western line of the fancy rat runs through those pits: colored oddities pulled from wild stock, then bred generation after generation as pets and show animals.

What Breeding for Tameness Does

The clearest evidence for what breeding does to temperament comes from an experiment that started with wild rats on purpose. At the Institute of Cytology and Genetics in Novosibirsk, part of the domestication research begun by Dmitry Belyaev, one population of wild-caught Norway rats has been selected in two directions every generation since 1972. Each rat's response to an approaching human hand is scored. The calmest breed together in one line, the most aggressive in the other.

By the time Frank Albert and colleagues published a genetic analysis of the two lines in 2009, they had been through more than 60 generations. The team found two regions of the genome with significant effects on tameness, and both overlapped regions linked to adrenal gland size and anxiety-related behavior, which points to fear and stress responses as part of what the selection changed. A separate region controlled white coat spotting and had no significant effect on tameness. Color and temperament can be inherited separately, which is what lets a fancier breed for both.

A rat nobody can handle never gets judged, so a century of fanciers keeping the easy-going ones ran the same selection with less paperwork. It shows in the pet: a fancy rat is one of the least likely small pets to bite, and much of what gets mistaken for a bite turns out to be something else.

A Social Animal, Measured

Two lab results describe the animal that breeding produced.

In 2011 Inbal Ben-Ami Bartal, Jean Decety and Peggy Mason at the University of Chicago put a free rat in an arena with a cagemate shut inside a clear restrainer. Over several sessions the free rat learned to open the door, quickly and on purpose. It ignored empty restrainers and ones holding an object. It still freed the cagemate when the setup kept the two from touching afterward. Offered a second restrainer full of chocolate, the free rats typically opened both and shared the chocolate. The authors took it as evidence of empathy-driven helping in a mammal outside the primates.

In 2016 Shimpei Ishiyama and Michael Brecht in Berlin tickled rats. The rats answered with ultrasonic calls, approached the hand, and made spontaneous leaps the authors called Freudensprünge, joy jumps. Neurons in the trunk region of the somatosensory cortex fired hard during tickling and also responded during play. In a setting that made the rats anxious, the calls and the cortical response both dropped away.

Where the Sewer Comparison Holds

Domestication changed the rat's temperament and coat, and left alone what a rat can carry. In early 2017 health officials traced an outbreak of Seoul virus, a hantavirus spread by rats, after a Wisconsin patient who ran a home rattery of about 100 Norway rats, bred mainly as pets, was hospitalized in December 2016. Investigators found infected people or rats at 31 facilities in 11 states, and six of those facilities had traded rats with Canadian breeders. Of 183 people tested, 24 had antibodies and three were hospitalized. Nobody died. It was the first known transmission of the virus from pet rats to people in the United States and Canada.

The everyday risk runs the other way. The disease a pet rat is most likely to face is its own, chronic respiratory disease from Mycoplasma pulmonis, which clean, well-ventilated housing does the most to hold off.

A fancy rat is a wild species that people spent 125 years choosing for its ease with them, and the lab work says what came out the other end: an animal that frees a trapped cagemate, shares the chocolate, and jumps when tickled. November 12th belongs to that animal, and to the fanciers who kept the records.

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