General Info

 

Fancy mice are of the domesticated Mus musculus species, also known as the house mouse. Male mice are called bucks and females are called does. Baby mice are called pups or kits.

 

Mice are small prey animals and are eaten by almost everything larger than them, including other rodents. Wild mice are usually very jumpy and skittish around humans, even if they are hand-raised, but domesticated mice that have been selectively bred for temperament can be quite comfortable with people and are more likely to walk away if they don’t want to interact rather than bite. However they do explore with their mouths and may gently nibble and clean fingers. Do not mistake this for an aggressive bite.

 

Mice live on average for one to one and a half years, but two or even three years is possible. Pregnant does gestate for about 21 days and give birth to an average of six to eight pups at a time. Litters of up to fifteen or twenty are not uncommon, however. Babies are fully weaned from their mother’s milk and sexually mature by four weeks of age but will not reach their full adult size until two to three months or more.

 

Despite both being rodents and looking similar- except for the size difference, naturally- it is estimated that Mus and Rattus (the mouse and rat genera, respectively) diverged on the evolutionary tree between 12 and 24 million years ago. Comparatively, Homo and Pan (the human and chimpanzee genera, respectively) diverged only about 5 to 7 million years ago. Mice, behavior-wise, are not like miniature rats. Rarely will mice desire petting from their human companions, but they can look forward to seeing you, sit in your hand or on your shoulder, and learn to tolerate gentle stroking and scritching. However, like rats, mice can be taught tricks such as spinning, fetching small objects, or running through a maze.

 

Mice from pet stores are less likely to be sociable to humans than ones from reputable breeders, however many skittish pet store mice can learn to trust their owners with time, patience, respect of boundaries, and lots of treats. Even mice that are not fond of humans are fun to watch and can still be enjoyable as hands-off pets.

 

Feeding

 

Mice need constant access to clean water, and uneaten food should be replaced every few days if it is not in a hopper (hardware cloth container holding the food off the floor of the cage that the mice can eat through) as it can become contaminated with feces/urine, or become wet and moldy. Lab blocks or pellets that are designed to be nutritionally complete, such as the Oxbow or Mazuri brand, are recommended over seed mixes, however seeds can be given as treats or scattered in their cage for foraging opportunities. Water bottles are strongly preferred over water dishes as mice will often soil or try to bury the dishes, contaminating the water. Bottles should be cleaned at least twice a month to prevent molding or bacterial growth.

 

Mice are naturally scavengers and will eat almost anything, but their main diet consists almost entirely of nuts, seeds, grains, and animal/insect protein. Fruits and veggies can be very sugary or watery and too much can lead to loose stools, so give those sparingly, if at all. Treats many mice enjoy include various nuts, sunflower seeds, millet seeds, cheerios, oats, and small amounts of applesauce, peanut butter, or plain yogurt.

 

Housing

 

There are lots of options for what kind of enclosure to keep mice in. The most common are pre-made bar cages sold in pet stores, aquariums or terrariums, and bin cages made from plastic storage tubs and hardware cloth. All cages have pros and cons but bins are most keepers’ top recommendation. They are lightweight, easy to clean, and customizable, and offer good visibility of the animals. Whatever the style, cages should have bedding changes done about once a week, more if you use paper bedding, and the cages should be deep cleaned once every 1-2 months. Do not use strong scented chemicals. A 1:100 bleach or vinegar to water solution is recommended for disinfecting and it should be wiped out with a wet cloth or paper towel, then allowed to dry before new bedding is put in and the mice reintroduced.

 

As prey animals, too much open space can be intimidating for mice, so they need lots of hiding places in their cages to feel secure. If you have a large cage and only a few mice make sure you fill it appropriately with hides or they may become nervous or skittish. Cage size is less important than enrichment in regards to mouse husbandry, however there should still be enough room to perform the natural behaviors discussed in the “Enrichment” section.

 

Fancy mice are social mammals, and females need to be kept in groups of two or more. Males can also benefit from company, but because they are same-sex aggressive, it is strongly recommended that they be kept alone unless they have been neutered. Some have reported success housing bucks with female African soft fur rats, also called multimammate mice. African soft furs are neither rats nor true mice but a separate rodent species entirely that are a bit larger than fancy mice and much smaller than rats. Their care is virtually identical to fancy mice, however they cannot interbreed. African soft furs are the only other species that fancy mice can safely be housed with.

 

Wood shavings such as aspen or kiln-dried pine is the recommended substrate for mice. Paper-based bedding can be used but must be changed more frequently as it is less effective at controlling ammonia levels. Corncob bedding is another option. Do not use cedar bedding.

 

Enrichment

 

Mice are very adaptable and can live in many different environments and enclosure styles/setups. However in order to thrive they must be able to perform certain natural behaviors. These primary behaviors are hiding, nesting, digging, foraging, chewing/grinding their teeth, and, of course, eating, drinking, and sleeping. Enrichment that allows mice to perform these behaviors are necessary for their happiness and health.

 

As said before, hiding places are important for mice to feel safe. Any small cardboard or plastic box can be used as a hide. Toilet paper tubes and crittertrail tunnels are also very fun for them. You can also buy hides in pet stores or online, and there are a number of fun shapes and styles available. Birdhouses with removable tops are great functional decor in a mouse’s cage.

 

The substrate in the cage should be deep enough for the mice to dig and almost completely cover themselves, if not even deeper. In addition to the main substrate, nesting materials can be given such as hay, alfalfa, tissues, toilet paper, paper towels, or newspaper. Paper can be given in sheets or crumpled up balls for the mice to shred themselves. Add treats inside the paper balls for extra fun and incentive. Do not give mice cotton balls or nesting “fluff” sold in pet stores as they can easily get caught in it and hurt themselves.

 

Like all rodents, mice have sharp incisor teeth that never stop growing. They are capable of grinding their teeth down themselves without extra help, but they still have a strong desire to chew things. If you feed pelleted/block food, that by itself is a good outlet. Other options include wooden or pumice blocks, raw or cooked bones, elk antlers, nuts in their shell, and hard dog treats. If you don’t see your mice chewing on what’s provided, try something with a different texture. Commercially available “Snack Shacks” are not recommended as they are basically made of sawdust and alfalfa with honey flavoring added and could cause blockages if too much is ingested.

 

Wheels are considered by many to be a staple for pet mice. Choose a wheel that does not have straight bars that their legs can fall through when running. Mesh wheels, solid plastic wheels, and saucer style wheels are all safe for mice to use. The wheel should be large enough for the mouse to run on it with a straight, not curved or arched, back. Their tails should not be forced to curl up over their backs while running. Keep wheels clean to prevent foot infections. Squeaky wheels can be greased with vegetable oil that will not harm the mice if they try to lick it.

 

While not absolutely essential, if your enclosure allows for it, mice can benefit from being able to climb. Items designed for birds such as ropes and ladders are fun for mice. You can also use wire shelf organizers or hammocks to make extra levels.

 

Common Health Problems and Symptoms

 

The most common illness seen in mice is an upper respiratory infection (URI). A mouse with a URI will sneeze, wheeze, click, gurgle, or make other noises. A healthy mouse is usually silent. Porphyrin, a red or brown colored mucus that can be mistaken for blood, may secrete around the eyes or nose. URIs are almost always caused by a bacteria naturally found in mice called Mycoplasma. When the mouse is healthy the mycoplasma is in balance and does no harm, but stress, an airborne irritant, or a weakened immune system can cause the bacteria to multiply and cause an infection. If left untreated the infection can spread and cause secondary more dangerous complications such as pneumonia, leading to death.

 

Mice that are stressed from being held or out of their cage may have loose stool but it should harden back up when they have been returned to their cage. Diarrhea that does not resolve itself quickly however can occasionally happen in mice and those with it should be monitored carefully for signs of dehydration or lethargy. A travel carrier lined with paper towels can be used as a hospital cage. A mouse with diarrhea but no other symptoms should be seen by a vet it if goes on for more than one to two days. Bloody diarrhea or diarrhea accompanied by lethargic behavior or labored breathing is a potential emergency and should be seen by a vet as soon as possible.

 

Mites and lice are common parasites that can be found on mice, that often come from their bedding. Signs of external parasites include excessive scratching, scabs, and bald patches. They are often invisible to the naked eye but can be tested for by a vet to confirm that the problem is not simply an allergy. To lessen the threat of parasites being transferred from their bedding, freeze or bake bedding before use, or sprinkle food-grade diatomaceous earth in the cage. Diatomaceous earth can also be used in addition to (not instead of) vet recommended parasite treatments.

 

Mice are experts at hiding pain and sickness so any indication of it should be taken seriously. By the time a problem is causing noticeable symptoms it can potentially be life threatening so keep an eye out for any general signs of pain or illness:

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• Unkempt, haggard appearance

• Lethargy, or excessive tiredness

• Labored breathing, unusually fast breathing, or open-mouth breathing/panting

• Sudden behavioral changes such as aggression or unusual calmness

• Clicking, wheezing, sneezing, sniffling, etc

• Pronounced, hunched back

• Weepy eyes or nose, with or without porphyrin

• Loose or bloody stools

• Excessive squinting when not sleeping or resting
   

General DON’Ts:

 

• Do not smoke or vape in your home with mice.
   

• Do not use chemical sprays in or near mice or their cages.
   

• Do not light scented candles, burn incense, or diffuse essential oils, or do so only in a well ventilated area away from the mice.
   

• Do not use cedar bedding.
   

• Do not pick up mice by the end of their tail.
   

• Do not try to pick up a mouse bare-handed if it is giving warning signs such as tail wagging, rearing up, or baring its teeth.
   

• Do not house fancy mice with other pet rodent species such as rats or hamsters.
   

• Do not allow other larger animal species such as cats or dogs to interact with your mice, no matter how docile or friendly they are. For their safety, keep predators and prey separate!
   

• Do not introduce new mice to your group without quarantining them first. Two weeks is minimum but four weeks or more is recommended.
   

• Do not allow sick or injured mice to be left untreated because you cannot afford a vet or there is not an exotic vet in the area. If treatment cannot be given in a reasonable amount of time they should be humanely euthanized to prevent ongoing suffering.

 

General DOs:

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• Give your mice their space when they want to be left alone.
   

• Pick mice up by the base of their tail, not the tip, or scoop them up from underneath.
   

• Herd them into a paper towel tube if they act like they may bite but need to be moved.
   

• Rearrange their cages and add new toys on occasion to encourage exploring.
   

• Replace soiled cardboard housing and toilet paper tubes with fresh ones.
   

• Let your mice occasionally try small amounts of new, safe foods for a varied diet.
   

• Introduce new mice to each other carefully and always in neutral territory.
   

• Love and cherish your mice and treat them like family! ♡