Pregnant mouse!

Question
Hey!

So, I recently purchased a second mouse because I figured my first mouse
was lonely.  I got the second mouse from a pet store where they do not
separate the males and females.  Also, she looks a bit more plump and eats
much more often than my other mouse.  If she is indeed pregnant, should I
separate her from the other mouse? Also, I do not know how to take care of a
mommy mouse and her babies!!  Thanks!  

Answer
Hi Gretchen,

It takes about 21 days from when a female mouse is impregnated until she gives birth, so you will only have to wait 3 weeks to find out if she is pregnant or just hungry.  You won't need to separate the two females unless they don't get along, or if either one shows aggression toward the pups once they're born.  If you have to move one, it's better to move the one that is not pregnant, so the momma doesn't have to get used to a new home right before giving birth.

The good news is that there isn't a lot you have to do for the momma or the babies.  Here's a general rundown:

First, make sure the suspected mommy is in a cage that doesn't have widely spaced bars.  Once pups start exploring they can be very mischievous, and anything they can fit their tiny heads through they can escape from.  Glass aquariums make excellent and inexpensive homes for raising a litter.

Next, make sure momma gets all the food and water she needs, and that her bedding is changed regularly.  Once the pups are born you won't want to disturb the cage for the first week, so the fresher the bedding, the less stinky it will get during that time.  After they are 6 or 7 days old you can probably feel safe changing the bedding - for this you'll need to remove momma and change the bedding at the farthest corners from the nest (this will be the dirtiest).  You can leave the nest in tact because mom will usually keep this area pretty clean.  Be careful not to toss out any babies, and don't touch them if you can help it until they have their fur coats.  After two to three weeks you can feel safe changing the entire cage - once again, remove mom first, then move the (probably rambunctious!) pups to a separate container, change, and replace.

If you'd like, you can supplement momma's diet with small amounts of dry cat food or scrambled eggs (made without milk, or with kitten milk replacement) for extra protein.

If she has a litter, she'll likely give birth in the middle of the night.  If you accidentally walk in on her giving birth to her babies, just turn the light back off and leave her alone for the night.  You can check on them as much as you like, but I wouldn't physically disturb the cage except for emergencies for the first 3-7 days (depending on how laid back she is).  Sometimes first time moms don't know what to do, so if you determine that you HAVE to remove the pups (if she is eating them all and you can't stop her, or if there are any complications), use this site to help you hand-rear them:  http://www.rmca.org/Articles/orphans.htm

Around 7 days old, start handling those little kids as much as you can.  Take adults out of the cage first, then rub your hands through the bedding and gently play with them inside of the cage.  Don't lift them out, just in case they roll off your hands or hop away.  The more you socialize them in this time, provided mom is okay with it, the nicer they'll be with people when they are older and, hopefully, the less they'll hop around during their "flea" stage.

The "flea" stage is around 2-3 weeks, different for every litter, when growing mice are extremely good at hopping.  They can surprise you and pop right out of your hand and injure themselves, so limit handling during this stage to inside the cage and be prepared for anything.

Around 3-4 weeks old the pups will start investigating the water bottle and adult foods.  You can facilitate this by lowering the water bottle to where small mice can reach it (be careful not to get it in the bedding where it will leak and flood the cage!).  They'll do the weaning all on their own, and once you are confident they know how to use the water bottle and eat normal foods they can be separated from mom.

It's a good idea to separate males from females before 2 months of age, though sexual maturity ages differ from mouse to mouse.  Females can stay with mom if you want, or can be rehomed, preferably in pairs or more since they are social creatures.  Once males have been pulled from the cage you can keep them together unless they start fighting - however, if you notice any fighting, you must pull out the aggressor immediately and be prepared to separate them all individually.  While sibling males sometimes get along, they can almost never be put back together once separated and are happiest with just you for a companion.  If you adopt them out, it's preferable to adopt out one by one so the person taking them home doesn't risk them fighting and possibly killing one another.

Which brings me to the last tip - adoption!  If you decide to rehome any pups you may wind up with, 6-8 weeks is a good age to start doing so.  Try the pet stores first, as sometimes they can put up animals for adoption for you.  Then you can try advertising them in the newspaper, on bulletin boards, or in local forums.  I wouldn't really advise Craigslist as a good way of finding new homes, as not only is it dangerous, but you can't be sure what sort of home the mouse is going to.  Lastly, if nothing else works and you have to find babies new homes, try talking to the local animal shelters.  Even if they can't take in rodents, they might know some nearby organizations that do or that can help!

Okay, those are the basics!  Let me know if you have any more questions.

-Tam