Approximately 40% of the earth’s entire mammal population is comprised of rodents. Antarctica is the only continent where rodents don’t live. It’s common knowledge that rats and mice are rodents, but so are squirrels, beavers, and porcupines. Dormouse A rodent’s teeth are specially adapted to chew dense materials. Rodents not only gnaw their food, they also create their homes and make their bedding by gnawing. For this reason, rodents’ upper and lower incisors grow throughout their lives, and must be kept constantly worn down. When kept as pets, this means a vital part of husbandry is supplying adequate hard toys for gnawing.

What are Rats?

Rats are the most intelligent of all the rodents, although squirrels run them a close second. In the wild, there are two species of rats: Rattus rattus, the roof rat, and Rattus norvegicus, the Norway rat. The two species cannot interbreed, but are still closely related. Roof rats arrived in America first, although an exact date is not known. Norway rats, however, were reported in the British colonies by 1775. Today, roof rats are found on both U.S. coastlines and in the American South. The Norway rat is more widely distributed in America, and is also common in Canada and England.

Roof Rats

Roof rats originated in India and are well adapted to tropical climates. They have long tails, large ears, and a somewhat delicate build. You will also see these animals referred to as tree, ship, and black rats.

Norway Rats

The Norway rat is the larger and more common of the two species. It is often called the brown, wharf, sewer, house, or barn rat. It is the direct ancestor of the domesticated rats kept as pets by enthusiasts. Norway rats originated in an area of Russia located near the Caspian Sea. They are heavier in build and have small ears. By nature this species is better adapted to cooler climates. Many of the qualities of the Norway rat have been selectively bred into companion domestic rats. They are highly adaptable creatures and opportunistic in their approach to survival. Their shopping list of abilities include skills at:
  • climbing
  • digging
  • jumping
  • swimming
They have been known to chew through both lead and concrete, and can leap as much as four feet / 1.22 meters. On average, a wild Norway rat weights 10-17 ounces / 284 – 482 grams. The largest ever measured, however, was 23 inches / 58.42 cm long and weighed 2 lbs. 12 oz. / 962 grams.

Domesticated Rats

Domestic rats are very similar in appearance to wild Norway rats. They are, however, extremely docile and receptive to being handled by humans. They are much less aggressive and predatory. Because domestic rats reach sexual maturity as early as five weeks and produce large litters, they reproduce quickly and easily in the pet trade. They are completely domesticated and would not be able to survive well on their own if turned loose. Socialization is necessary, however, especially in the critical period of age 2-4 weeks. Rats are highly social with one another and bond with equal strength to their humans, happily grooming, playing, sleeping, and eating with their people. Rat Because there are so many varieties of domesticated or “fancy” rats, all the various types will be discussed in the next chapter along with fancy mice.

What are Mice?

Mice are physically much smaller than rats. Some people feel this makes them cuter, but that is a matter of personal preference on the part of the owner. Luxurious whiskers flank a mouse’s pointed snout. When a mouse twitches those whiskers curiously, he makes for a most beguiling sight. Whiskers or “vibrissae” are also found on the upper lips, and a single whisker is located under each bright, inquisitive eye. Shorter whiskers are located on the chin. These specialized hairs help mice to sense movements in the air as compensation for their limited visual acuity. They do, however, have a keen sense of smell that further augments their navigational skills. A mouse uses his front feet in a very hand-like fashion to hold his food and to grasp objects. The front feet have four toes, while the back have five. Mice stand well on their hind feet, and will often assume an upright posture when they find something particularly interesting and worthy of investigation.

Common House Mouse

Mus musculus, the common house mouse is the best-known variety. It has an agouti coat, which, at first glance appears brown. Actually, each individual hair sports ticked bands of color. The muzzle and feet are more lightly shaded, and the tails is long and hairless. Mice use their tails to help them achieve their trademark acrobatic scampering. As they leap and climb, tackling unsteady surfaces with great ease, their tails function as both a counterweight and a “fifth” stabilizing leg.

Feeder Mice

Feeder mice are the most readily available type in the United States where they are sold as live food for reptiles, a practice that is illegal in the United Kingdom. These mice are raised with no regard to their genetic quality, and are usually poorly fed and housed in deplorable conditions. Feeder mice are cheap, and can be bought for $.30-$.50 / £0.18-£0.30 each. Typically, however, they can only be purchased in large lots unless a store manager can be cajoled into selling one or two as pets. It is difficult to obtain a healthy feeder mouse, but with love and attention, they can be turned into good companions. Unfortunately, however, feeder mice have a lifespan of one year or less as compared to 2 – 2.5 years for fancy mice.

Fancy Mice

The world of fancy mice, like that of fancy rats, is extensive and convoluted. The following chapter is dedicated exclusively to these elite animals, who are so pampered, many of them have fine and complicated pedigrees! They are, indeed, the royalty of the rodent world and are as highly prized by their owners as any other type of show animal.

Laboratory Mice

Both BALB/c or C57BL/6 lab mice make superb pets if you know someone who can acquire the animals for you. The BALB/c is an albino strain of the common house mouse, while the C57BL/6 is extensively used in human disease testing. They are prolific, reproducing easily, and have extremely robust and hardy constitutions.

Wild Mice

Wild mice do not make good pets. They are wary by nature, and don’t usually calm down even when treated with great kindness. Wild mice also carry zoonotic diseases, meaning they can be transferred to humans, a topic that will be covered in detail in the chapter on health.

What Are Dormice?

Dormice are also rodents, and are primarily found in Europe, with some species indigenous to Africa and Asia. They are members of the family Gliridae. Only one species is native to Britain, the hazel dormouse, a whimsical little creature that has found its way into many children’s stories and illustrations. Dormice range in size from 2.4 to 7.5 inches (6-19 cm) and weigh 0.53 to 6.35 ounces (15-180 grams). Many species live in trees and are nocturnal. Consequently, they are very well adapted to climbing. Although mouse-like in appearance, a dormouse has a furred tail and often over-sized eyes. Dormice are omnivores, but subsist largely on a diet of fruits and berries, flowers and nuts, and insects. They produce one to two litters per year averaging four offspring following a gestation period of 22-24 days. Depending on the region in which they live, a dormouse may hibernate for six months or longer. Their lifespan is roughly four years. These creatures are relatively new in the pet trade, with the most popular species kept as a companion being the African Pygmy Dormouse. Sometimes called “microsquirrels,” the species is small and agile. They are not pets that are good for handling or interactive play, but they are fascinating to watch provided you are a night owl. In the world of rodents, I would definitely characterize dormice as exotics. They aren’t for everyone, and are likely not a “beginners” rodent. Once a dormouse escapes, it’s extremely difficult to recapture. This is certainly not a pet a child can handle alone. I am including dormice in this book as a class of “advanced” companion rodent.

History of the Rodent Fancy

The history of rodents living with humans is long and convoluted, beginning with an involuntary relationship on the part of mankind. When we ceased to be primarily hunters and gatherers, shifting to a more agrarian existence, rats and mice happily moved into grain storage bins, helping themselves to our food. This is, in fact, how cats came to be domesticated as companions to human beings. They earned their keep in the granaries exterminating the rodents, fulfilling their side of the equation in one of the oldest of all adversarial relationships in the animal kingdom. Not all civilizations, however, viewed rodents as a scourge to be served up to the cats for the taking. In Asia, where mice are believed to have originated, the Chinese kept the tiny animals as pets as early as 1100 BC. The Egyptians accorded supernatural powers to mice, while the Greeks used them in rituals for divination and prophesy. (Alas, dormice faced a different fate in the same period. The Romans considered them a succulent edible delicacy!) Fancy rat taking care of its babies in front of white background The first mice and rats to be kept as pets by humans were undoubtedly wild specimens with the typical agouti or brown coloration. Both species, however, quickly adapted to domestication and were easily improved by selective breeding to enhance not only their temperament, but also their size and coat color, quality, and texture. The mouse fancy can be traced to 18th century Japan with the publication of the booklet, “The Breeding of Curious Varieties of the Mouse.” The hobby was present in England by the late 19th century where the National Mouse Club was founded in 1895 thanks to the work of Walter Maxey, the “father” of the hobby. In 1901 the National Mouse Club agreed to include rats at the request of Miss Mary Douglas, now considered to be the “mother of the rat fancy.” In 1912, the organization changed its name to the National Mouse and Rat Club. After her death, however, the interest in rats declined, and the club reverted to its original name in 1929. In roughly this same period, mice and rats were increasingly used in scientific research, most notably the genetic work of Gregor Mendel. This led to the breeding of more unusual specimens, which in turn stimulated greater interest in “fancy” rats and mice as pets. In January 1976, the National Fancy Rat Society was founded in Great Britain, and exists today in concert with the original National Mouse Club. The proliferation of the rodent fancy in the United States does not enjoy the same precise documentation. It’s likely that the first companion rodents in the U.S. were either wild mice or laboratory animals. In the 1950s, The American Mouse Club was formed, but was quickly abandoned. In 1978, the American Fancy Rat and Mouse Association was created, and is still the flagship organization for the hobby in the United States.

Rats, Mice, and Dormice as Pets

Rats make excellent pets. They are very easy to look after, as well as being clean and quiet. The same is true of mice, that are, by nature, gentle, loving, and curious animals. Although both species are smart, gregarious, and interactive, rats do edge mice out in the intelligence department. Pet rats easily learn their names, pick up extensive vocabularies from their humans, and are receptive to training. Rats also love to “ride” around on their people, and will quite happily cling to your shoulder as you go about your daily business. Due to their high level of intelligence, rats do need a lot of time and attention from their humans and will become unhappy and even sick if they don’t get it. Typically rats do live longer, but on average, both rats and mice survive only 2 to 2.5 years. Mice are the more fragile, weighing just 1-2 ounces (28.3-56.69 grams), but next to the African Pygmy Dormouse, they’re huge. An African Pygmy Dormouse has an average body length of 3.54 inches / 9 cm (excluding the tail) and weighs 0.63-1.05 ounces (18-30 grams.) All of these creatures are nocturnal, but rats are generally willing to adjust to your comings and goings. Mice can be especially given to nighttime escapes until they settle down to their life with you. Dormice? Don’t turn your back on those little guys or leave their cage top off for a second! Little Fancy Mouse Never make the mistake of keeping any of your rodent pets in the bedroom with you. Rats are busy by nature, and mice can be absolutely manic — as can dormice. Both of these creatures are either running at top speed, or conked out sound asleep. If your pets are in the room with you and they have a squeaky exercise wheel, sleep for you is not an option. Rats, mice, and dormice are all fastidious, and there will be no undue odor to the habitat if you do your job and clean up after your pets daily. Both mice and rats will pick one corner of their cage to urinate and defecate, which makes your job of spot cleaning each day much, much easier!

Discussing Life Span

Of the three animals, dormice will live the longest, but I do not recommend them as children’s pets. If, however, you are buying a rat or a mouse for a child, having a discussion about lifespan from the beginning is crucial. It is rare for a mouse to live more than three years, although it is quite possible with rats. How you care for these animals will clearly enhance their longevity. Not allowing your rats or mice to become obese, for instance, is very important in extending their life. This alone is an excellent reason for parents to be involved in the care of pet rodents. Rats and mice that get a steady diet of treats will not do well. Regardless, however, children must be prepared for the inevitable with this sort of pet. In truth, it’s always best to keep multiple mice and rats. This doesn’t negate the impact of the death of an individual pet, but it will ease the period of grief.


Neither rats nor mice are hypoallergenic. Rodents can, in fact, cause more allergic reactions in humans than dogs or cats. If your child has known allergies, it’s probably better to go with a pet turtle or lizard (bearing in mind that these animals can also carry salmonella.) Do understand, however, that allergies are specific to species. Typically the reaction is to the proteins found in the sebaceous and salivary glands. A child with an allergy to cats may not react to a dog or to mouse, for that matter. If you are concerned, have your child tested for the kind of pet you are considering acquiring. Better to be out the price of the test than to have a heartbroken child when the pet has already moved in and then must be re-homed.

With Children

As with any kind of pet, consider your child’s maturity level and ability to assume responsibilities before getting a rat or a mouse. Both animals are small and can be injured severely if handled incorrectly, or if dropped. Rats and mice must be fed correctly, and their cages must be kept clean. Rats, in particular, need daily interaction. Dormice, with their diminutive size and high activity profile, should only be considered as pets for older children who are extremely conscientious and reliable. In general, it’s best not to allow a child under the age of 9 to have sole charge of caring for either rats or mice. Even beyond that age, parents should take at least a supervisory role in the husbandry of the pets. Children of all ages should be properly educated on being gentle and kind with animals, both physically and verbally. Rats have better vision than mice, but both animals have acute hearing and will be frightened and stressed by sudden loud noises.

With Other Pets

When someone asks me if a pet mouse or rat will get along with the family dog or cat, I am often tempted to ask the person if they understand the concept of “prey.” No matter how “nice” your cat may be, a rodent looks like lunch in his eyes. The same is typically true for dogs, especially terriers who were, as breeds, developed to be “ratters.” The only way to keep a successful multi-species household when you mix rodents, dogs, cats — and ferrets, birds, and snakes, for that matter — is a strict policy of segregation. Your rodents will thank you!

Pros and Cons of Rodents as Pets

All of the following points should be considered before you acquire a pet rodent. Only you can decide if these things are pros or cons.
  • Rats and mice have relative short lifespans. Dormice live longer, but are not suitable pets for handling.
  • Rats, and mice to a lesser degree, are highly trainable. Rats enjoy being held, and some, as you will see, can even be harness trained, but they are still not as interactive as dogs and cats.
  • Mice must be kept in a habitat and not allowed to roam free. Some people do allow their rats to have free access in a room or rooms, but those areas must be stringently rat proofed.
  • Rats, mice, and dormice are all nocturnal, so you don’t want to keep them in an area where anyone is trying to sleep.
  • These are small creatures that can be easily injured if handled incorrectly or dropped.
  • All rodentscan trigger severe allergic reactions in people.
There are, however, certainly some clear cut advantages to keeping rodents as pets:
  • high intelligence
  • low expense
  • minimal space
  • cheap maintenance including food
  • no noise
  • clean
  • little to no odor
With fancy mice and rats, there is also the possibility of pairing your ownership of a pet with the hobby of showing the animal in competitive exhibitions. Continue Reading…

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