AFRMA

American Fancy Rat & Mouse Association

This article is from the Spring 1997 AFRMA Rat & Mouse Tales news-magazine.

Breeding & Stuff


Aggressive Female; Baby Mice; Male Rats Eating Young
Aggressive Female

Q I purchased a female rat around 3 weeks ago. At first she was very nervous, and I took her out in a blanket so that she wouldn’t escape. For the last week I have noticed that she eats a lot and has a big belly. When I bought her at the pet shop, they warned me that she might have babies later on. Unfortunately, now every time I feed her or try to take her out she jumps at me from where she hides and tries to bite me. Is she aggressive because she is pregnant? How many weeks does a rat stay pregnant? Should I do anything for her babies? Is she going to be nicer and tamer after giving birth or will she be even more aggressive because she will defend her babies? When I read about them, rats seemed like very tame and intelligent animals. I have to admit that I’m disappointed with the attitude of my rat. Laura Revil, Quebec, Canada

A By now your female rat has probably had her babies and hopefully all is well. The gestation period is 22 to 23 days. You won’t need to do anything special for the babies, just make sure mom has plenty of fresh water, food, and a clean cage. During the time she is nursing, you can give her good quality dry cat/dog food, table scraps, and mixed grain in addition to her lab blocks. You can handle the babies from birth to socialize them to people. The more you handle them, the tamer and nicer they are. If the mom won’t let you near the babies, you will have to take her out during the times you handle them. The babies will be ready to go to new homes when they are 5–6 weeks old. The temperament can be inherited, so if you handle the babies and they still aren’t very friendly, then you should get rid of mom and babies and find a breeder of pet rats to get a nice pet rat. Her being mean could be because she is pregnant or because of her breeding/genetics. Most rats that are bred and sold for snakefood aren’t bred for their temperaments. No care is taken to see that they are handled often and are used to human companionship. The breeding stock is not usually kept for their temperaments but rather for their production purposes. Also, the fact you were warned that she might be pregnant when you bought her is an indication that the pet shop does not separate the sexes and does not care if the females get pregnant. One suggestion would be to take the rat and her babies back to the pet shop and ask for a replacement—perhaps a male so you won’t have to worry about another possible pregnancy. Better yet, try to find a breeder of pet rats (someone who handles their babies and only uses breeding stock with nice temperaments, as temperament/personality is as much inherited as it is in physical handling). Use the guidelines in AFRMA’s “Pet Rats & Mice” caresheet “Choosing Your Pet” section to choose a pet rat. [Also, now the article Choosing Your New Pet Rats...] Both males and females make good pets—the only difference is males are calmer/docile and more laid back, the females more active and curious. If you decide to keep the mom and babies, perhaps you will want to keep a couple daughters if mom doesn’t change in her aggressiveness once the babies are weaned. This way, you have raised and handled the babies and will be able to tell if they will make suitable pets for you.

Baby Mice

Q I have two white mice (Sam and Samantha) who have just had a litter of baby mice. There are 15 or 16. I have no clue as to what to do with these poor mice. I need to know if there are any special instructions as to the care of the babies. I also need to know approximately how long they need to remain with their mother before they can be sold or given away. Abbey Marks, Enterprise, Alabama

A You don’t need to do anything special for the babies; however, mice can only nurse 10 at a time. This means that some may die if they can’t eat or the whole batch will be very small in size. If you had another mother mouse you could foster some to, that would be a suggestion. Another alternative would be to put down the very tiny ones and get the litter down to 10 or less. Culling is a common practice that many breeders use to help out the mom and the babies left. If you could tell the sexes, then culling out the males (since most everyone wants females for pets) would be another suggestion. If you knew of someone with a reptile that ate baby mice, you could sell them (or give them to them). Another method of culling is to take the runty babies and put them in a container or paper bag and put in the freezer (it is very quick). Whatever you do, the babies should stay with the mom 3½–4 weeks (4 weeks if you keep all of them as they will be very small and need mom that long). If you haven’t separated dad from the mom and litter, them Samantha will have another litter 3 weeks after the first litter was born (they can get pregnant right after delivering the babies so will be pregnant while nursing the first batch). The male mice usually are very good fathers, but keep in mind if you keep the mom and dad together, you will have baby mice every 3 weeks and therefore will need a place/people/friends that will take the babies as they are ready to go. Make sure Samantha has lots to eat and plenty of fresh water at all times. Also, make sure the cage doesn’t go too long before cleaning. Most mice will be fine when you touch the babies and clean up the cage as needed.

Male Rats Eating Young

Q Do male rats eat their young? Mr. Knop’s Science Class, Grissom Junior High.


A No, male rats do not eat their young. Usually, if you leave the male in with the female after they breed, he will help take care of the babies while the mother takes a break. However, if you leave the male in after the female gives birth, be prepared for another litter in 3–4 weeks. Female rats come into season and will breed again within 24 hours of giving birth. This is the same for mice. *

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Updated February 17, 2014