Mice and Rats

All today’s strains of domestic mice are descended from the house mouse (Mus musculus). They are often known as “fancy mice”, which simply reflects the fact they have been selectively bred for their coloration and markings. It is unclear as to when the domestication process began, but white mice have been known for more than 2000 years, being recorded during Roman times.

In Japan, the breeding of fancy mice was flourishing over 400 years ago, but this pastime did not really become popular elsewhere until the end of the 19th century, with the National Mouse Club being formed during 1895 in the UK. This laid the foundations for exhibiting these small rodents, which have since been bred in an ever-increasing range of varieties.  

Mice are quite shy creatures by nature, as reflects their nocturnal lifestyles. In fact, they cannot see in colour, but their night-time vision is greatly superior to our own, to the extent that they can see in what, to our eyes, would be total darkness. They also have relatively large ears, enabling them to hear well, while their prominent whiskers enable them to determine whether they can slip between gaps.

These rodents also possess a keen sense of smell, which helps them to find food. Their long tail enables them to sit up on their hindquarters, while their relatively short front legs mean they can hold food easily, and eat sitting on their haunches. By looking around from this position, so they are also better-placed to spot would-be predators. If disturbed at any stage, mice will always seek to hide from danger, with their agile paws enabling them to climb without difficulty.

Housing

There are a number of ways of accommodating pet mice. Some owners like to use a converted aquarium for this purpose. This has the advantage of being able to provide very spacious accommodation at low cost, and a secure ventilated hood should ensure the mice are safe from any cats within the home. A glass aquarium will be quite cumbersome and heavy however, and this is important because mice require their quarters to be cleaned very thoroughly because otherwise their urine - especially that of males - will create an unpleasant smell in the room where they are being housed. An acrylic aquarium will be a better option, being relatively lightweight, and easy to handle and clean.

The potential drawback of this type of enclosure can be the lack of ventilation though, and especially if a group of mice are being housed together, this can leave them vulnerable to respiratory ailments, to which they are susceptible. As an alternative, you can purchase a pet rodent cage, of which there are various styles available. Their general design consists of a detachable plastic base, combined with what is usually a two tier interior. The floor level in this case is connected to the raised platform above by a ladder.

Accommodation of this type gives better ventilation, and also allows you to interact more directly with the mice through the sides of the cage. The mice will also be able to climb around their quarters, using the space more effectively. There is a real risk that if you have a cat, it is more likely to be attracted to the rodents in this type of housing however, to the extent of sitting on top of the cage and frightening them badly. 

The door must also be kept firmly closed, so as to prevent accidental escapes. In fact, it may be worth obtaining a special clip or even a small combination lock which you can use for this purpose, rather than just relying on the cage door closure. Laboratory-type cages are sometimes recommended for pet mice, but these look unattractive and may make it hard to reach the mice easily.

The floor lining of their quarters is significant, as far as the health of the mice is concerned. Don’t use sawdust because this will irritate their prominent eyes, and may also cause them to sneeze repeatedly. Coarse shavings, sold specifically as pet bedding, is suitable however, and will prove to be quite absorbent. There have been fears that pine or cedar shavings might be dangerous though, with their scent irritating the respiratory tract of mice exposed to them and possibly causing liver damage too, over a longer period.

Shredded paper bedding is now a popular alternative, and recent introductions include bedding made from corn cob, which is both safe and easy to change. Some clean meadow hay is also recommended, partly to provide a sleeping area, but also as a source of dietary fibre, which can be eaten by the rodents. The mice must also feel secure, so provide sleeping areas lined with paper bedding where they can hide away, especially during the day. This does not need to be anything elaborate - a flowerpot on its side may suffice, or a small wooden nestbox, as more commonly-used by birds.

It is generally not a good idea to provide a cage wheel in their quarters, particularly as mice may injure their long tails, even with a closed wheel of this type. They often like cardboard tubes however, which are easily replaced once they become soiled.

Feeding and general care

For a long period, there were no prepared foods on the market for mice, but now the situation has changed quite dramatically. Packeted mouse food, in the form of a variety of cereal seeds and some oil seeds like sunflower is one possibility. It is important not to over-rely on sunflower seed though, as this can easily cause obesity, particularly in the case of older mice. Seed itself is also deficient in a number of key dietary components, such as some of the amino acids such as lysine which are the building blocks of protein. 

As a result, specially-formulated pellets offer the best feeding option, containing all the key nutritional requirements needed by fancy mice. These pellets must be kept dry, and the mice themselves are likely to drink more water on a diet of this type, compared with a seed mix. Supplementing their diet in either case with a range of fresh foods is recommended.  These can include pieces of carrot or celery, but remove any uneaten items of this type at the end of the day, so there is no risk of them becoming mouldy.

Always provide drinking water in a bottle which attaches to the side of their cage, or is suspended from the roof in the case of a converted aquarium. This will ensure that they can have access to a fresh supply of drinking water, without any risk of their bedding becoming wet, or the water itself being fouled by their droppings. Position the spout at a convenient height so the mice can drink without difficulty.

Offer their food in a heavyweight pot, which they will not be able to tip over. These can be purchased from pet stores, and are easy to clean. Another useful purchase will be a small acrylic container with a ventilated lid. This will allow you to keep your pet safely confined while you clean out its quarters. Wear disposable gloves, and be prepared to wash the cage each week, using a special, non-toxic disinfectant which is safe for use with small pets and a small scrubbing brush. This will prevent any build-up of an unpleasant mousy odour, as well as protecting their health. Rinse off the components thoroughly, and ensure the base especially is thoroughly dry before reassembling the unit. The water bottle can be cleaned with a small bottle brush.

Mice themselves are quite fastidious about grooming, and you are likely to see your pet using its front paws for this purpose. There is usually no need to carry out grooming yourself - simply stroking the fur with your fingers should be adequate. Mice do need to be trained to allow you to pick them up without struggling or even biting, which can otherwise prove very painful and is likely to cause bleeding because of their very sharp incisor teeth at the front of the mouth.

Remember that mice have poor eyesight and will instinctively bite if they feel threatened. Youngsters will soon overcome their fear of being handled, if you do this from a early stage, soon after acquiring your pet. Always allow a mouse to sniff your hand before picking it up, and try to scoop it up from beneath, cupping it gently in your hands rather than grabbing it around the body, as a predator would do in the wild. If you need to restrain the mouse, put your fingers either side of the base of its tail. Before long, you will find that the pet will sit happily in the palm of your hand, and may even start eating here, if offered a treat.   

Varieties

In total, there are now over 800 different recognised varieties in the case of the fancy mouse - far more than in other domestic pets, although many of these are quite rare, being kept largely by exhibition breeders. By far the most popular are the solid-coloured or self varieties. White mice are very widely-kept, possibly because their coloration is far-removed from the natural grey agouti shade associated with their wild ancestor. As they grow older however, such mice often develop a slight yellowish tinge to their fur.

At the other extreme, there are self blacks, which are jet black in colour, although they appear grey at birth. Lighter in color are self chocolates, which should be of a dark shade. This particular variety has been known in Europe since the 1870s. One of the most attractive colours is the self red, which is of a rich, orangish-red shade. The shiny nature of the coat is reinforced if this is combined with the satin mutation as well. A slightly paler form of the red is the self fawn.

Amongst the more popular patterned varieties are the tans, such as the black and tan. There should be a clear line of delineation, with the upperparts being coloured - black in this case - while the lower edge of the body and the underside are always tan. So-called fox mice are similar, but their underparts are white.  They can be bred in many colours too, such as the chocolate fox.

Another patterned form which is now seen quite often is the Himalayan, being named after the gene responsible for this colour change. It first cropped up during the 1920s in a laboratory in the United States. Although they are apparently white at birth, young Himalayan mice soon develop the characteristic areas of dark fur - either black or chocolate, depending upon the variety - on the so-called “points” or extremities of their body. This mutation corresponds to that seen in Siamese cats, so that the dark areas are confined to their face, ears, feet and tail.

Breeding

Mice are social creatures, and it will be better to start out with two or three females, called does, which can be housed together. To prevent unwanted offspring, it is important to be able to sex them with certainty. The gap between the anus and genital opening is relatively close in does, compared with bucks. Avoid keeping males or “bucks” as pets, because they tend to become much smellier once they mature.

The gestation period is about 19 days. The young are born helpless, and the nest must not be disturbed at this stage. The so-called pups grow rapidly, and will be able to feed themselves by three weeks old. Litters are large, often being comprised of 10 or more individuals.

Health problems

Mice are generally very healthy, although as they become older, so their coats often become thinner. They typically live for about two years. In old age, they often develop signs of stiffness, which is frequently caused by osteoarthritis, although this may be treated by a painkiller - ask your vet for advice. The likelihood of swellings on the body increases with age, as does the risk of internal tumors which often cause weight loss.  Kidney problems too can result in similar symptoms.

Loss of fur may also be linked with the diet, as excessive levels of oil, resulting from too much sunflower seed, can have this effect. Adjusting the diet accordingly should soon lead to an improvement. Lack of dietary fibre can cause ‘barbering’, with mice nibbling at each other’s fur, sometimes including their whiskers. Changing the diet should again improve the situation, especially offering more fresh food.

If the lack of hair seems to spread, or results in circular patches, this will need to be checked by a vet for signs of the fungal ailment known as ringworm. Although it is rare, mice suffering from this condition can spread it to people, and so must be handled carefully.

Repeated sneezing and a nasal discharge are signs of a respiratory illness. This is again something that will require veterinary treatment. A course of specific antibiotics can help to clear this up successfully.