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One of my areas of interests that relates to fancy mouse breeding is that of behavior and domestication. My goal is to produce animals that animals are high quality as far as there temperament is concerned so I think understanding domestication and temperament development is important to fancy mouse breeders.

Domestication is an evolutionary process by which animals become adapted to human exposure and their captive environment. This occurs through a variety of genetic changes as well as experimentally induced behavioral changes that reoccur every generation (Price 2002). There are a variety of behavioral, anatomical, hormonal, and neurochemical changes that occur during domestication (Albert et al. 2009). One behavioral change in particular that is associated with domestication is increased tameness (Price 2002).

Behavior is anything an animal does that is both observable and measurable. Behavior occurs in reaction to an animal’s internal or external environment (Grier & Burk 1992). A good example of this is wheel running in mice (Mondragón, Mayagoitia, López-Luján, & Diaz 1987). Wheel running is a behavior because its something that can be seen happening and the distance traveled on a wheel can also be measured. Tameness is a characteristic of certain behaviors that are associated with the process if domestications (Goto, Tanave, Moriwaki, Shiroishi, & Koide 2013).

Tameness includes two general types of behavior. The first is the willingness to approach humans. The second is reduced avoidance of human interaction. There are many factors that can influence tameness. Habituation to human contact, positive reinforcement in association with human interaction, and genetics all play a role (Price 2003 and Goto et al. 2013).

Measuring Tameness can be achieved using the active tame test, passive tame test, and the stay-on-hand test. The active tame test is designed to measure the willingness to approach humans aspect of tameness. Its involves placing the animal in an open chamber and placing a hand in the chamber and slightly wiggling the fingers. The hand is kept about 10cm (or 4in) from the mouse. Time spent moving toward the hand, contacting the hand, and jumping are measured. The passive tame test is similar in that it involves placing the animal in a chamber and actively following the mouse around the chamber. If the hand makes contact with the mouse then the person performing the test attempts to touch the animal for as long as possible. In this test time spent heading towards the hand, jumping, and moving in general are measured. The stay-on-hand test is used to measure response to forced human interaction. Animals are placed on an open palm and time that the mouse remains on the hand is measured (Goto et al. 2013).

In a laboratory setting these behaviors can be measured using video recording and other equipment (Goto et al. 2013). In the home setting these tests do not need to be carried out in such an exact manner but rather these concepts should be kept in mind and casual observations can be utilized when selecting animals for breeding. The more your selections are based on accurate observations the better your results will be.

Acquired Tameness

Acquired tameness can be developed by frequent contact with humans in a neutral context. This is called habituation (Price 2002). Related to acquired tameness is the habituation to the captive environment where animals become accustomed to being exposed to captive life (Ochieng’-Odero 1994). It can also be induced by means of positive reinforcement such as when feeding the animal. The animal comes to associate human contact with something positive such as being food (Price 2002).

Handling of pups at a young age increases tameness as well as reproductive ability (Price 2002). Studies have shown that when animals, such a rats, are handled as pups then grooming they receive from their mother increases. This intern reduces the stress response when they are adults. This reduced stress may be a factor in improved reproduction later in life (Liu et al. 1997).

These findings suggest that a fancy mouse breeders should handle their mouse pups regularly in an effort to improve tameness, improve fertility, and reduce stress. However some fancy mouse breeders feel that mouse pups should not be handled regularly. Fancy Mouse Breeders want to select mice that are genetically predisposed to tameness. They feel that handling the mice make it more difficult to tell if a mouse as acquired tameness or inherited tameness (citation needed).

Inherited Tameness

Improved tameness can be achieved by selectively breeding the tamest individuals over many generations (Trut, Oskina & Kharlamova 2009). Although tameness can be inherited little is known about what is happening as far as the genetics that are involved (Albert et al. 2009). Many domestic animals come in a variety of colors that are not found in the wild, and this has led some to suspect that these genes may be influencing domestication and tameness (Albert et al. 2009).

However, studies in rats showed no connection between white spotting and tameness, Dispite these finding there could still be a relationship in other species (Albert et al. 2009). Its interesting that in studies breeding foxes and rats white spots appeared more frequently in tame lines than they did in aggressive lines. This happened even though the only trait being selected for was tameness or lack thereof (Albert et al. 2009).


Goto, T., Tanave, A., Moriwaki, K., Shiroishi, T., & Koide, T. (2013). Selection for reluctance to avoid humans during the domestication of mice. Genes, Brain and Behavior12(8), 760-770.

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Ochieng’-Odero, J.P.R. (1994) Does adaptation occur in insect rearing systems, or is it a case of selection, acclimatization and domestication? Insect Science and its Applications 15, 1–7.

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Trut, L., Oskina, I., & Kharlamova, A. (2009). Animal evolution during domestication: the domesticated fox as a model. Bioessays31(3), 349-360.

Albert, F.W., Carlborg, Ö., Plyusnina, I., Besnier, F., Hedwig, D., Lautenschläger, S., Lorenz, D., McIntosh, J., Neumann, C., Richter, H. and Zeising, C., 2009. Genetic architecture of tameness in a rat model of animal domestication. Genetics, 182(2), pp.541-554.