Q: I recently got a mouse from a friend; she says that it is about a year old. About two weeks before I received the mouse, it was living with a male mouse. Every time someone touches the mouse or even goes near her, she squeaks and squeaks. She is very fat, and I don’t know whether she could be pregnant or not. She’s eating a lot.
A: If your new mouse was in with a mature male mouse (that’s any male mouse more than 5 weeks old) she is probably pregnant. If she is pregnant you will know fairly soon, because mouse gestation is only about 20 days.
A pregnant mouse must have a secure cage (preferably a tank or solid side cage to avoid drafts) with lots of clean bedding material and a small igloo or box without a bottom where she can build a nest. Once your mouse tucks herself away in her nest, leave her alone so she can give birth and tend to her little ones.
You will know that the mouse babies have arrived when you hear soft peeping noises from the nest, but resist the urge to peek for at least 24 hours. If the mother mouse seems nervous, leave her and the babies alone for the first few days, then you can start touching them gently.
Best wishes to you and the new little ones, and make sure you remove the male mouse babies from the cage when they become sexually mature at 5 weeks old.