American Fancy Rat & Mouse Association

This article is from the Winter 1999 AFRMA Rat & Mouse Tales news-magazine.

Breeding & Stuff

Large Litter of Rat Babies

By Helen Pembrook

Q I just rescued a female rat from the pet shop two weeks ago and for the last couple of days noticed she was getting rather fat. I just thought it was because I was feeding her really well since she didn’t have the best of care at the pet shop. Well, this morning I heard squeaking noises coming out of her cage and when I checked, there were BABIES! A whole bunch of babies! I counted 16 of the little red squeaking critters. I have several questions as I’ve never had baby rats before.

  1. What is the gestation period for rats?
  2. What is the normal litter size for rats? Do they always have this many?!
  3. Is the mother rat going to be able to care for 16 babies? What will I need to do for her?
  4. When will the babies be ready to go to new homes? I can’t keep all 16 as I only have the one cage. I’ve heard you wean them at three weeks.
  5. What are the babies called? I know dogs are called puppies, cats kittens, etc.
  6. What do I do if she can’t care for the babies? I’ve heard the term “culling.” What exactly is this.

A 1) The gestation period for rats is 19 to 22 days, the average is 22.

2) The average litter sired in my experience is 8 to 14 although as few as 1 or as many as 26 have been cited in some sources.

3) Some rats seem to be perfectly suited to handle huge families with relative ease, others are simply abysmal at the job of motherhood. Most rats land somewhere in the middle. While having all the instinct and intentions of being a good mother, some can become physically over-taxed especially with gigantic litters. This leads to weight loss, dehydration, and generally poor condition. If this occurs, the mother may not be able to produce enough milk to properly feed her kittens. It is also possible that the mother could die.

One problem with such large litters is that rats only have 12 teats (nipples). This causes intense competition among the young, leaving the smaller ones to be shoved out of the way and not allowed to eat as much as they need to thrive and grow. All of the kittens will suffer, some may die.

There are several ways to deal with this situation. If you are lucky, you may be able to find someone with a mommy rat that has a small litter that you can foster some of the babies to. Most rats seem to be of the mindset that if it’s a baby, it must belong to them, no matter what the relative ages of the other “siblings.”

You can bottle feed some of the babies with a baby bird feeding syringe with a fine tip, small doll bottle, small piece of tubing on the end of a syringe, etc., and kitten or puppy formula which you can buy at the pet store. But keep in mind that if you decide to do this, the kittens must be fed every 2 to 3 hours around the clock.

Another option is culling some of the young. The decision to opt for this particular course of action is a personal one and should be governed only by one’s conscience.

If you want to try to just help the mother care for her babies, you can add extra protein and fat to her diet via a good quality cat food (dry or canned) and yogurt and hope for the best. However, you should keep a close eye on her and the kittens and re-evaluate the situation on a daily basis to see if one of the other options should be considered.

4) Many of the commercial breeders will send out babies at 3 weeks of age. While it is true that the kittens are eating solid food at this age, to grow up and become truly healthy adults, they need their mother’s milk for at least one more week. If possible, kittens should stay with their mother until 5 weeks of age, though with a large litter that may not be possible. If the mother seems taxed or some of the babies are becoming weak, you could take the larger, healthier kittens out at 3 to 3½ weeks and supplement their diet with a good quality dry cat food, yogurt, dry whole wheat bread, oatmeal, etc.

5) Baby rats are referred to as kittens.

6) Culling is the removal of some of the young if the mother can’t take care of them. Usually one starts with the runts during the first week, then those that are mismarked during the second week, and finally those animals with small ears, short or thin tails, and other undesired traits. The number is gradually reduced to that which your female can successfully raise.

What happens to the babies that are culled? Most people who practice culling put the animals down humanly one way or another. Personally, I take and donate mine to a raptor rehabilitation center where they are put to sleep FIRST and THEN used to care for the birds. I feel that this is a good use for the animals I don’t want and benefits birds that are a treasure to our environment and country. Other people may not agree.

Culling is a deeply personal decision which you alone must make. *

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Updated March 20, 2014