Estrus and Conception
- The male and female mouse can be placed together at any time during the estrus cycle, as mice are social animals. If aggression is observed, attempt regrouping the pair with other appropriate-age mates. According to the Transgenic Mouse Facility at the University of California, Irvine, the doe's estrus cycle lasts four to five days, and the pair will breed several times during this time. Most female mice will be pregnant within six days of being placed with the male.
The pair can be caged together to ensure a successful pregnancy until the 14th or 15th day of the pregnancy, at which time the female should be moved to a birthing cage. Breeding pairs left together can result in infant mortality, as some males may kill their offspring to stimulate a return of the female's estrus cycle.
- While the barren female mouse doesn't require much more than a quality commercial mouse diet, a pregnant doe has additional nutritional needs, including increased fat and protein, that should be met to ensure a healthy pregnancy. About halfway through the pregnancy, you should increase these nutrients. Many people add a small dog bone, such as a Milk Bone, or a small amount of scrambled egg in addition to the commercial feed to supplement the pregnant doe's diet.
Birth and Birthing Needs
- The pregnant doe will often build a nest of shavings and dig a hole to give birth to her young. Once the nest is built, refrain from handling her or her young.
If housing several pregnant mice together, be certain that they are bred at the same time to ensure births occur are within a day or two of each other. Many female mice will share nursing responsibilities. The younger and weaker pups may be ignored in favor of the infants that are more mobile and aggressive about feeding.
Gestation and Weaning
- Baby mice are born hairless, pink and blind, and are very susceptible to cold. At seven to 10 days old, they begin exploring outside the nest and tasting different foods. They develop quickly and can be safely weaned between 19 and 21 days old. Juvenile mice reach sexual maturity quickly, so male and female litter-mates should be separated by four weeks of age.