I (responsibly) breed rats to humanely cultivate for boa fodder. It is very rare for a female to have less than 8 babies. They can start breeding at 6 weeks of age. It takes 21 days for the rat to have a litter, and she can be conceived the same day of having the litter. They usually have 10-22 babies. So lets say she has 12 babies, 6 of them female. The next month, those 7 females would have about 84 babies. In 4 weeks, the babies would be weaned. Hmn...