Is my mouse pregnant? How can I prepare?

Question
Hey there,

Yesterday I got a feeder mouse from my petstore,as a pet. I was told it's a male, but have had several people tell me female. I am also confident it is a female. Since both males and females were mixed together in the feeder tank, what are the chances she is pregnant? If she is, is there anything I need to do to prepare?

She still looks normal mouse size, but she seems a little chubby which I would think is odd, for so many mice living together. I've been Googling the topic, but it hasn't been super helpful.

Thanks in advane!

Answer
Hi Addylnn,

Unfortunately, the only way to tell is to wait and see if babies arrive.  The best way to prepare is to keep her food bowl and water bottle filled, and her cage clean.  You can offer tissues or ripped up toilet paper for nesting supplies, but as long as she has some kind of fluffy bedding, she'll take care of it if the time comes.  If she doesn't already have a hide  of some kind, that's a great idea, too, so she has a safe place to build her nest.

Mice have a gestation period of 21 days, give or take a couple, so if you don't see babies by about three and a half weeks past when you brought her home, she's not pregnant.  The thing about new mice is they are usually sold very young, so a little bit of fattening up is to be expected.  :)

If babies do arrive, don't disturb the cage for the first week.  After the first week, you can "spot clean" the rest of the cage as it gets dirty, by only removing bedding on the far side and replacing with clean.  Don't remove the mice to do it, just a quick switch out, and watch for babies just in case!  Momma will keep the nest clean on her own, so don't worry about that.  The babies will wean themselves in about 4-5 weeks - you'll know they are ready to separate out when they start drinking from the water bottle on their own reliably.  At that point, males should be removed from the cage.

If you have any other questions, just let me know, and congratulations on your possible litter!

-Tam