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.
The best age to obtain your future pet is at the age of 5â8 weeks (mice), 6â9 weeks (rats) (females older then 6 weeks may be pregnant if housed in community cages) so they grow up with you. The average life span of rats is 2â3 years; mice 1â2 years. The average body length of adult rats is 9â11 inches; mice 3â4 inches; with an average tail length of 7â9 inches in rats and 3â4 inches in mice. The average body weight for rats is 350â450 grams for a female, 450â650 grams for a male; mice 30 grams each sex. There have been a few adult male rats that weighed 2 pounds! Meeting the basic needs of a pet rat or mouse is neither complicated, time consuming nor expensive.