Rats do have a wide range of sizes when they give birth, but the average size of a litter is around eight to 18 pups. These babies are blind and deaf when they are born and should be kept in a quiet room for seven days after birth. After they are weaned, the female rat should have a two-month rest period before having another litter. This will allow her to build up her strength again.
A healthy doe should be fit, with a shiny coat that looks like it could run a marathon. When she is picked up, her coat should feel firm and lively. She should be easy to handle and tame. A fit doe will grow up until she is about a year old. This is because the pituitary gland produces growth hormone during lactation.
Rats have unlimited litters in the wild, but pet rats must be monitored and separated to prevent pregnancy. A typical litter size is six to 12 baby rats, and the number of babies in a litter depends on several factors. Rats can have litters every three to four weeks, so they can produce as many as 17 litters in a year.
Studies have shown that litter size influences the growth and metabolic status of neonates. A small litter size is associated with fast growth and reduced feeding competition during nursing. Small litters may also increase the risk of metabolic disorders later in life.