Breeding Mice - The Methods

Selective Breeding
Much More Than "Random Breeding"

Everybody who raises mouse litters can claim to be a mouse breeder.? Raising a few litters is random breeding, raising several litters perhaps more serious breeding.? But how does random breeding differ from selective breeding? When does random breeding turn into selective breeding?

At some point each breeder notices that in her animals there are some faults and that because of that they do not do as well in shows than animals of another breeder. Therefore the breeder tries to combine her animals in a way that the offspring would be better than their parents. And like without noticing it, the breeder has changed from random into selective breeding.

Selective breeding can be described as being systematic breeding of animals in order to change certain qualities in them. With selective breeding of pets, the question is about systematically improving the animals to resemble the written standards laid down for them. With mice this includes improving their colour/markings, type and - as they are pets - also their temperament and health.

How is the breeder able to improve the quality of her animals? Three key words are Goal, Feedback and Sustained effort. This seems to be clear, does not it. In reality this is not always the case. The goal is lost easily as the years (or even few moths) pass by as the first litters were not what they should have been. Feedback is taken overtly critically or even arrogantly (the judge does not know a thing, there is nothing wrong with my animals). And last but certainly not least, sustained effort is the first one to be forgotten - the breeder becomes interested in other hobbies than the breeding of mice.


The goal is one of the most important things to consider before even starting to breed mice. Make a decision what kind of mice you really want and stick to that decision.

If the breeder acts like a weathervane -- breeding Champagne Tan today, Black Eyed Cream tomorrow and after that long hair mice - it is easy to understand that she cannot improve a thing, she can only scratch the surface.

It is not sufficient for the breeder to decide that her mice will win prizes. In fact it would be far easier for the breeder to buy good mice from other breeders and compete with them.

You should consider following details:

- What colour, marking or coat variety you wish to breed?
- What is the quality of mice in your area?
- What is the quality of your mice, are they better or worse than the general level?
- How many mice are you able to keep?
- Are there others breeding the same varieties you chose?

Choose only one colour or marking and stick to that decision. It does not matter if that variety does not do well in shows at first. You will have more reason the be proud of your breeding once it starts to show some results.

Decide the colors and markings you want to breed and develop. Do not get greedy. Choosing too many colors you will not be able to concentrate well enough in any of the colors without getting some hundred breeding mice. Monitor closely the level of quality in the colour you have chosen home and possibly abroad (mainly Britain). If the general quality is quite bad in your area, you may have to consider importing mice. Find out what are the good and bad qualities usually present in this colour. Compare your animals with the general level of quality, are they clearly better or worse. Here you should be as critical and honest as possible. If your animals are better or at least of the same quality, you have far better chances of succeeding in your selective breeding. If your animals are clearly worse, you should consider changing your breeding stock. Starting selective breeding in poor quality animals really takes time and patience.

How much space you have for your mice gives some limitations to your breeding. If you do not have a spare room for your mice, you cannot have so many of them. Mice do stink even though you changed their beddings every single day and the more mice you have, the more time it takes to take care of them.

Cooperation with other breeders is very important. Selfishly aiming at your own benefit and getting "fame" is shortsighted, which eventually will harm yourself. In some point you will need new blood in your strains and if the general level of quality in mice is quite bad, it is really difficult to get a good breeding mouse.


The only way to monitor the development of your breeding is feedback and analyzing it. Write down information on each litter, so that you can remember even after years of time what kind of mice each combination produced. Write down faults, but also successes. Also follow the development of the mice you have bred after they leave home; what they grew up to be, how do they make in the shows and what kind of offspring they get.

Compare the offspring with the parents. Are they better than their parents? What qualities have they inherited? Can you tell what qualities were inherited from the mother, and what from the father?

One very important factor is the uniformity of a litter. This does not seem to be clear to all breeders, which I find amazing. After all, uniformity tells a lot about the genetic make up of the mice. A litter with one excellent mouse with the others being mediocre or worse, is not a good litter when it comes to selective breeding. The sole excellent mouse can carry the poor qualities of its siblings and pass them on to its offspring. A uniform litter is a sign that they will also have offspring of uniform quality.

One of the most important places to get feedback from are shows and different kind of breeders' meetings. In shows you can present your animals to the judge and to other breeders as well. Follow the judging closely and listen what the judge has to say about the animals you have bred. If possible, present a breeder's class even though in your opinion your animals are not good enough to win the class. You will still get the judge's opinion on the overall appearance of your animals and whether you have progressed or declined in your breeding. Some judges give valuable advice on how to breed out certain faults in your stock.?

It pays to show your animals even though you are still only starting your breeding. Particularly with rarer varieties the judge will be very interested in the animals shown. At the same time you are helping the judge to form an over all opinion on the quality of the variety in question.

There is always a danger of becoming "blind" to the faults in your own animals. Usually the breeder becomes upset if the judge remarks on the faults present. It is easy to understand that at this stage the selective breeding work usually comes to a halt. It cannot develop further, if the breeder sticks to her beliefs on the quality of her stock. Have a critic's eye when you monitor your animals and think if it is worth using and are you heading in the right direction. Remember your goal.

Sustained Effort

The results of selective breeding are often visible only after years of work, but it is hardly possible to ever breed the perfect mouse. With good luck you can get a Best of Breed mouse from the first litter, but more probably it will take you several generations to breed a winner. So, be patient and aim consistently towards the goal.

Sustained effort is needed especially when they are setbacks in the breeding work. These can be hereditary illnesses, unusual aggressive behavior or other faults. In the worst case the whole stock may die of food poisoning or a deadly disease - this has happened. This kind of situation is very depressing for the breeder, years of work have come undone and she feels like there is nothing to be done.

If there are other breeders working on the same variety, the situation is not really that bad. You are able to start anew by obtaining good animals of your own strains from other breeders. As the you have long time experience on your variety, you will soon reach the level of quality you had, sometimes even better.

If you were the only one breeding the same variety, it takes a considerably longer time and effort to create everything anew. Still, you are able to avoid many mistakes you did the first time around and the result may be a stock of far better quality than before.

Even though your breeding is guided by the standards of excellence, you should always remember that you are breeding pets. The temperament and health of your animals are of utmost importance. They should be tractable and friendly, with mice the does should be able to get along easily. Different hereditary illnesses are a warning signal, implying that your breeding is going into wrong direction. If hereditary illnesses do occur, never sell these animals to pet shops. They may end up getting bred from and therefore contaminating other strains of mice as well.

Text by Minna Koivu.
English translation by Satu Karhumaa.