Notes on Breeding:
Raising your mice is not a decision to be taken lightly, and you absolutely must consider what you will do with any resulting babies. Most pet stores already have established suppliers. You should also carefully consider the temperament and health of the mice you are breeding. I’m not advocating keeping mice for the average owner, but if you stumble upon a pregnant female, or maybe from a pet store, the information here may be helpful.
Age of Sexual Maturity:
Mice reach sexual maturity at 4-6 weeks. However, females should not breed for the first time until they are 8 to 12 weeks old.
Estrus cycle:
Female mice go into estrus (estrus) every 4-5 days (this is the time when they can reproduce and accept males). They will go into heat within 12-28 hours after giving birth and a few days after weaning.
Pregnancy time:
The gestation period of mice is usually 19-21 days.
NOTE: Mice can be bred shortly after giving birth. If they reproduce while nursing a litter, the gestation period may be longer (about 28 days).
Litter size:
Litter size varies widely; 7-12 pups per litter is considered average, but more is not uncommon (a litter of 20 is very likely).
Weaning age:
Mice are typically weaned at 21 days, but should ideally be housed with their mothers until 3.5 to 4 weeks of age. However, separate male pups from female pups by 4 weeks of age.
