Fancy Mouse

House mice originally lived in steppes, semi-steppes and semi-deserts in the Mediterranean and Southeastasia, where they foraged for grass seeds. They began to follow humans about 8000 years ago, when humans first practiced agriculture and found a paradise in the granaries. Wild house mice need at least 35-40% of their own body weight in food, a lot more than their domesticated relatives. They always live in family groups, forming huge groups at times. Solitary mice were never observed and wouldn't have a good chance of survival anyway, since house mice need the protection of their group. They have a varied social life, which will be explored in the chapter „Social Structure and Behaviour“.
Wild house mice have turned into pests, but not all humans see them as such. White mice, very rare in the wild, as considered sacred in some cultures. In India, there's a temple dedicated only to mice, similar to the better known rat temple.
Mice were also used in sacred ritual, they were considered lucky or were believed to cure disease when taken as medicine.
They have been bred for about 2000 years in China and for about 300 years in Japan, from there they arrived in Europe about 160 years ago. They began their sad carreer as laboratory animals in the 1960s.

Fancy mice come in many colours: pure white to yellow, orange, red, blue, lilac to pure black and marked in combinations of these colours. Some colours come with red eyes, such as pink-eyed whites (aka albino mice). These animals are more sensitive to light and may be susceptible to disease like glaucoma. It's better to use no flash when photographing them.
The most healthy variety is the normal shorthaired, smooth-furred mouse. There are other varieties, but most of them suffer from vairous health problems. You can find more information about those breed here.

Basic Information

Fancy mice weigh between 25 and 50 grams, very small animals may weigh as little as 5 grams, adipose individuals as much as 100 grams. Their body length lies between 8 and 11 cm (3-4“), plus a tail that's 7,5-10 cm long.
Healthy mice have a body temperature of 38.5 to 39.3°C (101.3 to 102.7°F), slightly higher than that of a human. They breath 100 to 200 times per minute and have a heartrate of 300 to 800 beats per minute.
Mice perceive their surroundings very different from the visual oriented humans. Since their eyes are on the sides of their head, mice have a vision of almost 360 degrees, but don't have stereoscopic vision and have trouble judging distance and depth. They are very good at seeing movement, but almost no colour. They probably can see in the red and yellow part of the spectrum and it is believed that they may be able to see parts of the ultraviolet spectrum.

They have a much better sense of hearing, their ears can be moved in all directions independently of each other and can hear ultrasonic sounds, which are inaudible for humans. Acoustic communication between mice is mostly ultrasonic.

The sense of smell is equally well developed and helps mice with finding their way around as well as with communicating. They mark their territory with smells, follow scent trails than they can perceive even in total darkness and use smell to choose their partners and to know who belongs to their family and who doesn't. Mice have a extremely sensitive organ of equilibrium in their inner ear which allows them to move confidently even on thin branches or ropes. That sense of equilibrium must be trained and mice who didn't have the chance to do so move clumsily until they have learned how to use it again.
Their whiskers (vibrissae) help them to explore their surroundings even when there's no light. With those and vibrissae on the side of their body they can judge if they will fit through a hole.

Fancy mice have sixteen teeth, four are constanly growing incisors with a very strong layer of dental enamel. That layer is yellowish to orange with healthy animals, deficiencies in the diet can make it turn white. Behind the incisors is a gap, followed by twelve molar teeth that do not grow constantly.

You can find pictures of various fancy mice in the gallery.

Fancy mice are easy to feed and to care for compared to other exotic rodents, but they do have certain needs that must be met to keep them happy and healthy.
Females and neutered males live usually very peacefully together, which makes them the ideal pets for someone who wishes to keep one of the many mouse species. Males that are not neutered, should be kept only by experienced owners because of their aggressiveness towards each other and otherwise complicated social behaviour.
It's true for all of them that they are not suitable for children, they are too small, fragile and react badly to stress.
Fancy mice, particularly unneutered males, have a peculiar, intensive smell and it's a good idea to make sure that you can tolerate that smell. If you are sensitive to smells, fancy mice are probably not the right pet for you.

Fancy mice are usually not very shy and not aggressive to humans, so handling them is easy and they let themselves be picked up. If the mouse doesn't like to be handled and you need to take it out of the cage for some reason, you will need to catch it: Either use a toilet paper roll for the mouse to hide in or you catch it with your hand by seizing it from the side, quickly, but gently. Trying to catch them from above is not a good method because it makes the mouse think that it's being attacked by a predator and this will only stress it. Holding a mouse by the tail is not recommended unless you have no other option. In that case hold the mouse at the base of the tail and support its body with the other hand.

If you want to sex your mouse, hold it gently at the base of the tail and lift its body so that the front paws are still securely on the ground or you put the mouse in a glass or clear plastic bowl to take a look from underneath. The first method is better suited for adult mice, for juvenile animals it's better to use the bowl method. Mice can retract their testicles and juveniles in particular do that.

If the mouse needs to see a vet, handle it as described above. For injections etc. and examinations of the head the mouse can be fixated by holding it at the base of the tail and at the fur in the neck. You can take only the sick mouse to the vet unless you keep a group of unneutered males, then it's better to take the whole group to avoid fights when reintroducing the sick mouse. Escaped mice can be caught with a live trap or with a spoon net or pet carrier.

Fancy mice are very social and mustn't be kept alone. Contrary to what you might have heard, single mice won't get tame faster and they are in no case happy alone, even if it may seem so from the way the mouse may seek your company and attention. Every single mouse suffers from being kept alone and you cannot replace the company of other mice even if you spend a lot of time with your mouse. Being kept alone can make the mouse sick, it can cause problems such as stereotypical behaviour or the mouse may even die.
Mice need other mice to play, groom, cuddle up to feel secure and to communicate with (which mice do with ultrasound, not audible for humans). That's why you need to keep at least two mice of the same sex (or females with neutered males). If you have enough room and the mice get along, groups can be 30 individuals strong or even bigger. With females, there's the danger of bickering and harassment, so it's often a good idea to introduce one or more neutered males to stabilize the group.
Keeping unneutered males is a bigger problem. Even if you keep only small groups or just two males, there will be fights and they will get serious and dangerous very fast. It doesn't matter if the males are related, there's only a 5% chance that the males will be able to live together without fighting all their life.
Introducing a juvenile to an adult male can be successful, but there will probably still be fights once the juvenile is sexually mature. The only solution is neutering the juvenile at the age of about three months.
Keeping females and unneutered males together is not an option because of the enormous number of babies they will produce. In a worst case scenario, two mice produce over one hundred babies in just three months – there's no good way to handle a situation like that. Apart form that, the babies may suffer from genetic defects, causing such things are malformed babies or organ failure ect.
Mice mark their territory with urine and faces, that's why they smell stronger when you have just moved them into a new home. If you try to get rid of the smell by cleaning the cage and the toys, maybe even with scented cleaning agents, the mice will only mark their territory again and even more thoroughly. Cleaning the cage just with hot water gets the cage just as clean and will keep the mice from marking it again because they still recognize their smell.

Types of behaviour
Mice have an established pecking order and strengthen it with different rituals and behaviours, grooming is an important part of that. Here is some behaviour shown towards humans and their meaning:

The mouse shies away from your hand or freezes, with half-closed eyes: It's scared und not sure what to do. Keep offering your hand and avoid any sudden movements, especially if you have shy mice.
The mouse watches its surroundings with perked ears and is sitting up on its hind legs: It's curious and wants to know what's going on around it.
The mouse grooms itself extensively, while you're watching: It feels secure and isn't bothered by your presence. Mice that clean themselves only quickly and hastily are nervous or scared. A mouse that starts to fidget, tries to run away or even nips your finger when you are holding or petting it, wants to be left alone.
Tooth grinding can have several reasons, depending on the situation: Extreme anger, fear or a serious threat.
Gnawing the cage bars can also have different reasons, but the most common one is boredom. It's a sign that the cage is too small and/or too boring/empty. In that case, try offering the mice a bigger cage with lots of toys and things to climb on, gnaw on and hide in. Otherwise the cage gnawing can turn into a stereotypical behaviour and then it's very hard to get rid of it even in a huge cage. If you have a mouse or mice with such a problem, offer them a big, interesting cage, the gnawing may get less and in any case, they will feel happier.
If the mice gnaw the bars only occasionally, they are searching for a way out of the cage because even when the cage is big and interesting, they are curious to find out what's behind the bars.
Tail wagging is a threat and a sign of extreme anger or agitation.

It doesn't matter what colour of fur your mice have, they are all fancy mice and have the same needs. The minimum size for two females and/or neutered males is 100x50x50cm/40x20x20“ long, wide and high. For two unneutered males a cage that's about 60x40cm/24×16“ long and wide, to avoid fights. But there's no guarantee that they won't fight in a cage of that size and it's not a good solution for animals that love to climb and run anyway. You will need to find a solution that takes their aggressiveness, their curiosity and their need for a big cage into account.
If your cage is made from wire net with square opening, the openings mustn't be bigger that 12mm/1/20th of an inch. Normal cage bars shouldn't be more that 8mm/1/30th of an inch. Don't use chicken wire because the mice can get caught in it.

Regardless of what you use as a cage, the mice will need at least one, better several second levels. Suitable for mice are normal cages, homemade cages or so called mouse castles. A mouse castle is a table with a lining to keep the bedding from falling off, the mice stay on the table because they are afraid of heights and won't jump off. You need to make sure that they cannot reach the table legs or anything else to climb down, though. Tanks and terrariums are not very suitable for mice, it's hard to offer climbing toys and second levels in them and there may be a build up of ammonia which can cause damage to the mice's lungs.
There are many suitable types of bedding: Wood shavings (non-resinous wood!), hemp or flax bedding (often used for horses) or even bark mulch (stay clear of cocoa mulch, it's toxic for almost all animals). As nesting material you can offer hay and straw, hemp- and cocosfibres, unscented toilet paper or paper tissues. Most mice gladly accept a digging area filled with sand and/or soil. You can offer them leaves, as long as the trees were not treated with pesticides and the leaves grew at some distance from the ground and a street.
A sandbath can also be offered, although it's used more as a toilet than as a bath. To prevent damaging the fur, always use chinchilla sand, never bird gravel or cat litter, the bird gravel is too coarse and the cat litter is too dusty and can be harmful when eaten.
Almost all natural building materials are suitable as furniture and toys for mice: Cork bark and tunnels, tunnels made from wood as well as roots and branches, which are also cheap when gathered outside. Again, make sure the wood is not treated with pesticides, doesn't grow near a busy street and disinfect the roots.
Hiding places can be made from wood, clay or pottery. The form doesn't matter much as long as the entrance is at least 3 cm/1.2“ wide to prevent the mice from getting stuck. Nesting boxes for parakeets or nests for finches are popular as well as cocohuts or other toys made from coconuts.
Hay is great for behavioural enrichment: Haynests can be bought at pet shops, but you can just fill a basket or a mug with hay and let the mice explore it and build their nest in it.
Ropes train the muscles and coordination and can be used with other materials to build mouse playgrounds – get creative!
Stones are a long-lasting addition to the cage furniture, for example shingles or clay tunnels (meant to store wine bottles in) or stones gathered outside, as long as they are disinfected. Toilet paper rolls or other cardboard rolls are cheap and make great chewing toys, they can also be used to catch mice that won't allow themselves to be handled. If you offer a digging area with soil, keep the soil slightly moist to prevent it from dusting.
It's a question of faith whether mice need a wheel. If you want to offer one, it should meet the following criteria: A diameter of at least 20 cm/8“ to prevent back problems as well as a rolled up tail. The wheel must be completely closed on one side, otherwise the mice may get trapped while getting on or off the wheel. The running surface must also be solid to prevent the mice's feet from getting caught in the spokes.
Last but not least, you will need a water bottle, a food dish and a dish for fresh food. Water bowls get dirty very quickly and some mice tend to bury them, causing all the bedding around it to become soaked. Food dishes should be put in an elevated place to prevent this.

Mice have a rapid metabolism and digest any food they eat in 3-4 hours. That's why they need comparatively much food, about 25-30% of their body weight per day.
The main diet should consist of a mix of seeds and grains, small seeds should make up at least 60% of that. In addition to that, the food may contain dried vegetables and small parts of fruits, oily seeds and nuts. Dried herbs are a good source of minerals. It's important that the food doesn't contain many processed things like popped wheat or pellets but rather just the seeds.
Apart from offering the food in a dish, you can let the mice work for their food by offering them millet spray, flax- or oatseedheads. Storebought rodent biscuits or treat sticks are not recommended due to their high sugar content.
Vegetable or fruit skewers are a lot of fun for the mice as well as sprouts from wheat, barley, oat, herbs and grass grown in unfertilized potting soil and offered with the soil.
The mice should get more vegetables than fruit because fruit is only a small part of their natural diet. Germinated seeds are full of vitamins, a good choice in the winter. The following foods are unsuitable or toxic for mice: Cabbage (almost all kinds) since it causes flatulence which is dangerous for mice, uncooked potatoes and potato greens, papaya, avocado as well as houseplants.
Mice are not vegetarians and need animal protein. The most natural form are insects such as mealworms, butterworms or silkworms. You can try to offer live crickets or locusts, but most mice don't know what to do with them.
If you don't want to offer them live insects, you can substitute them with hard-boiled eggs or dried insects.
Sunflower seeds, pumpkin seeds, peanuts and raisins make good treats. Organic raisins are much less polluted with pesticides. Storebought treats like drops are in most cases not suitable because they contain way too much sugar and are often too fatty.

Example for a physiological combined food ¹⁾:

The given data about raw protein and raw fat fits to mice kept as normal pets. For pregnant and lactating females increases up to 22,00 % (protein) and 4,50 % (fat).

Mice give birth to huge litters to ensure the survival of the species and it's the same for both wilde mice and fancy mice. After a gestation period of 21 days a female can give birth to a litter of up to sixteen babies and is ready to mate only hours after giving birth, so the next litter will be born three weeks later. Successful breeding is not a sign that the mice are comfortable and that all their needs are met because they will breed even under bad conditions.

Mice babies open their eyes when they are 14 days old and explore their surroundings, but they are nursed until the end of the third week. Even though the babies are not longer relying on their mother's milk at that time, they should stay another week with their mother to learn from her. They are ready to breed at an age of 28-46 days and need to be separated into males and females then they are 28 days old. If you want to breed your mice, you need to wait until they are fully mature at an age of three to four months. If females are bred at an earlier age, that can cause her to eat her babies, to neglect them or she may give birth to dead, weak or sick babies.

Since they breed so quickly, you need to make sure that you don't get both sexes in one group. Pet shops are not reliable in that respect, better get your mice from a rescue organisation or from a reputable breeder, they are experienced in sexing mice.

Developement of the babies: 1-2 days old: the babies are naked and blind 2-4 days: pigmentation is visible 3-5 days: the ears open 10-14 days: the eyes open 14-16 days: the babies begin to eat normal food, but are still nursed by their mother 19-28 days: the females are ready to breed when they are 28 days old, the males when they are about 30 days old and should be separated from their mother and sisters at 28 days. The female babies can and should stay with their mother for some time. Fancy mice can reach and age of 1.5-2 years, some get older.

Since they have been domesticated and bred for such a long time, mice are delicate and prone to certain disease. The most common disease are respiratory infections, which should be treated with antibiotics. Ammoniac can cause or worsen respiratory disease like colds or pneumonia, that's why the cage needs to be warm, dry, well-ventilated and at the same time draught-free.

Tumors are another common disease, but not all of them are malign. Often they are swellings of the adipose tissue and the growth rate of tumor varies a lot. That's why a tumor is not necessarily a death sentence, if it grows slowly, it's possible that the mouse can die from natural causes before teh tumor has grown so huge that the mouse needs to be put to sleep. Sometimes it's possible to operate on tumors, see a rodent vet to find out if there's a good chance of success. Other disease are relatively rare with fancy mice. You will need an emergency reserve of about 100-200 Euros for medical emergencies. The vets needs to be knowledgeable about rodents and not all vets are. See http://www.rmca.org/Vets/ to find a good rodent vet in the US.

Female and neutered males are usually fairly easy to introduce to each other. In mot cases it's enough to let them meet on neutral ground or you put them in a small pet carrier. If your mice are not as peaceful combine both methods: Let the mice meet on neutral ground and after a few hours put them in the pet carrier just with bedding, food and water, maybe some hay to hide in. There they stay for the night. If everyone stays calm, they can move into a small cage, again only with their bedding, food and water. After another day, they can move into their normal cage (remove all toys and levels and clean the cage with hot water and vinegar to remove all smells). Add one piece of furniture/one toy per day, then the second levels. If the mice fight at any stage, go back on step and try again.
Introducing neutered males to each other is a bit more complicated, although it gets easier the longer the males have been neutered. After six months or so the chances of success are pretty good, but freshly neutered males react just like unneutered males, so it's better to wait at least four weeks. If the males knew each other before and had been fighting seriously so that they had to be separated, it's better to wait eight weeks or longer or keep them separated.
It's sometimes recommended to put unneutered males in a small pet carries to introduce them because they won't defend their territory in such a small space. That's not a solution because the males will fight as soon as they have more room, some will even fight in the pet carrier. If the mice act highly aggressive towards each other and have serious, bloody fight, stop the introduction – you won't be successful and it's only stress for the mice.
Since the chances of success are so very low, it's better not even to try. Unneutered males that have been fighting and had to be separated cannot be introduced to each other again, whatever method you use. You would risk the lifes of one or all mice.
A solution is introducing single male fancy mice to natal rats or deer mice, but it's not ideal and neutering is always to be preferred. For more information on co-housing several species see the chapter below.

If you have decided that fancy mice are the right pet for you, you have several options to get some. First try animal shelters and rescue organisations, for example www.rmca.org since many shelters don't accept small pets. If there are rescues to be found, but not near you, try organizing a transport. There are many websites and mailgroups for this – usually it's dogs and cats being transported that way, but it's worth a try. Here's a good place to start.
If you have set your heart on a certain colour, you have a good chance to find such a mouse at a rescue. The other option are reputable breeders, again www.rmca.org is a good place to start your search. Sometimes breeders can be found at small pet/exotics expos.
Buying your mice at pet shops is the worst thing you can do. There's a high risk to get a sick, too young or pregnant mouse (or all three). Many employees at pet shops can't sex mice reliably so there's a good chance that you are given a male and a female.
Depending on what kind of enclosure you want and what you want to use as toys and furniture, the expenses for mice can be very different, between 50 or 200 Euros. Running costs of course depend on how many mice you keep, what you use as bedding ect., but 20-50 Euros per months should be allowed for. Apart from that, you should have a reserve fund for vet visits of 100-200 Euros, depending on how many mice you keep.

Keep in mind that co-housing species should only be tried by an experienced owner and it's not a method to save room, the animals will need even more room than before.
Fancy mice are usually friendly towards other species and so are well suited for a co-housing project. You must have the room to house both species separately if it doesn't work out, though, since there's always the risk that the species won't get along.
In an ideal case, you have already kept both species separately for some time and are well-informed on their needs and peculiarities, that way you avoid co-housing species that don't fit well with each other.
If you have a male fancy mouse that cannot be neutered due to old age or other reasons, you will need to find a partner as fast as possible and if you can't find neutered males, then natal rats or deer mice are the best option. Spiny mice can also be company, striped grass mice or gerbils are not suited for this. The latter would kill them!
When co-housing a male fancy mouse with a different species, the size of the enclosure is defined by the needs of the other species. If you want to keep one group of each species, the enclosure should have a size of 1- 4 qm, depending on the other species. If you are not sure that you can meet all the needs of all the species, then it's better to refrain from such an experiment.

Sources
http://www.diebrain.de/ma-index.html
http://www.farbmaus-rassezucht.de/
http://www.pfotenstube.at/voegel/maus.htm
http://www.projekt-biomaus.de/