The stomach has three types of contractions: There are rhythmic, 3 per minute, synchronized contractions in the lower part of the stomach, which create waves of food particles and juice which splash against a closed sphincter muscle (the pyloric sphincter) to grind the food into small particles.
7 What is the gestation period, how many babies do they have, and when are they weaned? 1  The gestation period for rats is 19â22 days, for mice it is 17â21 days.  Rats and mice average 8â12 babies in a litter, but can have as few as 1 or as many as 20.
Overview of Reproductive Process. As mice breed throughout the year, a single female produces between five and 10 litters annually. Each brood can contain up to 12 young, but the average litter size hovers around five or six babies. Young mice grow quickly and usually only need three weeks before they're fully weaned from their mothers. The pests achieve sexual maturity after five to seven weeks.