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Mice/Is my mouse pregnant


QUESTION: I have had these mice for about a month or more two males and a female the pet shop said it would be fine two keep them together i thought she was pregnant about two weeks ago she was really big I thought she was going to have them but she still hasn't I don't know if she's pregnat can you help please and how long until she has them if she is pregnant she is the one with a lot of white

Also would the males kill the baby mice ?
Thank you

ANSWER: Hi Hayley,

I didn't receive a photo with either question you sent - do you want to try to send a picture again?

The pet shop was incorrect - males and females should ONLY be kept together when actively trying to breed them, and even then, only for two weeks at a time.  This allows plenty of breeding opportunities, but removes the male before the pups come, which is the best option for the momma.  If the male is kept in the cage when the pups come, many things can go wrong:

- The male may eat the pups (not always, but sometimes they are seen as competition)
- The female may be stressed from the male's presence, and eat the pups herself
- The male may impregnate the mom immediately (she can become pregnant the same night she has the pups), leading to serious injury to the mom, concurrent litters (which can lead to malnourished or trampled pups), stress, and/or cannibalization.

If you are aiming to ensure the health of the female after any litters are produced, and avoid costly vet bills (because pregnant and nursing moms cannot have most medications), please remove the males immediately.

Another thing they were wrong on is housing more than one male together.  With the exception of juvenile males from the same litter who have not yet reached breeding age, males should never, ever be kept together, especially when breeding.  Male mice can and do fight to the death, and can go from peaceful to fatally injured literally overnight.  There is no way to predict how long they will go before fighting, especially when complicated by hormones.  When not housed with a female, they should be kept in their own cages well apart from each other.  Males who can smell other males are in constant stress, sort of fight-or-flight, and will also be poorer breeders as a result until the problem is fixed.

With all that in mind, here are my suggestions for successful breeding, and what may be happening with your female:

1.  First, look at WHY you are breeding.  What traits are you trying to pass on to the next generation?  Even feeder mice should be bred mindfully and with a purpose.  Are you trying to make cool colors or coat types?  Docile personalities?  Intelligence?  Healthy breeders?  Great pets that don't bite?  Look at the traits you want in your baby mice and pick which male you are breeding from accordingly.  If you put in two males and get a terrific (or awful) litter, you won't know which one was responsible!

2.  Then, come up with a breeding schedule.  This is what I used and worked very well for me:  Put one male in with one or more female for 14 days, then remove him and clean the female's cage completely.  Mice have babies 21 days after conception.  Since they could have conceived anywhere from day 1 to day 14, you can expect baby mice somewhere between ONE WEEK after removing the male to THREE WEEKS after removing the male.  If one month has passed since removing him and still no babies and no sign of health problems, try again!  If babies DO come, they will take 4-5 weeks to mature.  There should be absolutely no breeding with that female until all pups are weaned after that point and separated from her cage.  For more details on what to do when babies arrive, please just ask, and I'd be happy to give you some info and resources.  If you pair the same two mice for 2-3 cycles and they just will not breed, try a different pairing until you know if it is the male or female who is a poor breeder.  Genetics could be part of any problems, as well as health, age, weight, stress, and nutrition.

3.  If you remove the males today, using the math from above, you can expect babies anywhere from TONIGHT until THREE WEEKS from today.  Be patient, keep stress on her to a minimum, and keep her cage clean, as you won't want to disturb her once they do come.

4.  Since mice are usually sold quite young, at 4-6 weeks of age, they may not have been mature yet.  If pups do not come but she seems fatter, it could just be that she was still growing up and had natural weight to put on around her middle!  I do not recommend breeding mice before the age of 3 months, ever, as it can lead to major complications and health problems.

Hopefully this helped you figure out what's going on with your mice and your breeding set up!  Please let me know if you need clarification on anything or have any other questions.


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QUESTION: Thank you that helped a lot I will put them in different cages now

ANSWER: That's great! I'm glad I could help.

I see the photo now, but it's not a great angle for determining if she's prego or chubby. I'd say it's definitely possible, so prepare for babies and see somewhere in the next three weeks. :)


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QUESTION: Thank you :) what do I need for when the baby's arrive in the cage and one of my mice has lost some hair on his butt what could that be from
Also I have another female and I think she has been mateing with one of my males
Would it be alright if I put the two girls in a cage together I think there both pregnant and keep them together while they have baby's ?
There's another picture of her


If the males are together, he could be losing hair from fighting.  Overgrooming, mites, allergies, and a host of other problems could be to blame, however, so a vet is usually your best first bet when you notice something wrong.  Remember, if there is a health problem with a mouse, that mouse should not breed until well after the problem is completely resolved.

In my experience, it is safer to keep pregnant females apart.  This prevents a not-so-good mom from hurting a good mom's litter, and prevents lactation problems if one mom is feeding too many or not enough pups.  Both points are especially important if they are not due within the same couple of days, and since you can't be sure when the first momma's litter is due, it would be better to house them separately through the weaning of their respective litters.

When the pups arrive, mom will do most of the work.  Give her plenty of space and do not disturb her during the first week.  After one week you can begin spot cleaning her cage, by removing soiled litter from OUTSIDE the nest only (she will keep the nest clean until the babies start wandering out of it).  Be sure there are no pups hiding in the litter you discard!  Pay close attention to mom's body language.  If she is disturbed by you invading her space, either rushing to cover her pups or coming out to distract and/or attack your hand, leave her be and give her another few days before trying again.  Keep plenty of food and water available during this time.

When the pups start to wander out, around a couple of weeks old, they may begin chewing on solid foods, but they are not yet weaned at this point.  Offer safe snacks like stale bread or mouse food blocks for them to practice chewing at.  Make sure the water bottle is placed low enough that when they are ready at 4-5 weeks of age they can try to drink from it, but not so low that it floods the bedding.  Once ALL of the pups have proven they can drink on their own from the water bottle, and do so reliably, they will stop nursing from mom and can be separated.  Males should be removed and put in their own cages - you can keep them together if necessary until about 2-3 months of age, but I would not push it past that, especially if there are females in the same room.  At that point it would be better to give them their own individual spaces, one cage per male.  Females can be housed in groups of however many you have room for without crowding, and even left with mom.  Write down when they were born, when they were weaned (4-6 weeks of age depending on the mice), and anything else you don't want to forget.  Use this information to keep track of their ages, so you don't accidentally breed a female before she is three months of age.



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I can answer questions regarding mice as pets, mouse behavior, color and coat genetics, breeding techniques, and general health questions. I can help with caging and setup, nutrition, social issues, and what to do in most mouse emergencies (such as unplanned litters, injuries, fighting, etc.). I can also assist with questions pertaining to orphaned mouse pups, weaning litters, and questions of mating and birthing. I cannot answer questions about exotic or wild varieties of mice such as spiny or pygmy mice. *****FOR EMERGENCIES, anything requiring immediate medical intervention, PLEASE take your mouse to a professional veterinarian or wildlife rehabilitator who works with mice as soon as possible! IMPORTANT RESOURCES: Raising Orphaned Mice: Orphaned Mice Videos: Natasha's Your First Mouse: General Mouse Help: Mouse Info and Exotic Breeds:


I have enjoyed the companionship of mice nonstop since 2004, and spent a year caring for them in a lab where I learned a great deal about their breeding, social needs, and health. I spent a few years breeding them, specifically working with albinos, marked mice, angora mice, and satins. My education never stopped - I am learning something new every day from current and well-established research thanks to the wonderful folks at the Jackson Laboratory, as well as from my wonderful mousey friends online. I also love learning from my terrific questioners here on AllExperts - you folks keep my passion for these amazing animals alive and well!

East Coast Mouse Association - expired, American Fancy Rat and Mouse Association - expired

Partial University for a B.S. in Microbiology, Partial University for a 2-year degree in Veterinary Technology (RVT cert), C.E. classes in pathogens, aseptic technique, genetics, and applications

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