Back-to-Back Pregnancy

Question
I saved two mice from the pet store from getting sold as food. It kinda was a spur of the moment thing. I assumed they were both males and bought one cage. During my 4th weekly cage cleaning I found little pink babies. I hooked at pictures online and they were about 2 or 3 days old. I quickly put them back, took the male out and in a different cage. Apparently I didn't take him out soon enough. Now I can tell she is pregnant but hasn't given birth yet. The first litter has their eyes open and are one week from being separated boys from girls. Should I take them out early to make way for he new babies and give the mom a cage of her own? I don't know what to do with them.

Answer
Hi Kayla,

Females go into estrus right after giving birth, so you can expect the new litter around when the first pups are about 3 weeks old, give or take a couple days.  The first litter needs to be removed as soon as possible, because they run the risk of trampling the new pups for milk when the second litter is born.  Be wary of wire cages, as they tend to squeeze through the bars and get away.  You can tell they're ready to wean once they figure out the water bottle, and they'll probably already be trying solid foods once they start to walk out of the nest.  If they're three weeks and you think mom is about to give birth (rearranging the cage, making a new nest, getting awfully large), you can pull them out early and supplement their diet with moist foods (apple with no seeds, stale bread soaked in kitten milk replacement or water) until they learn how to drink.  To help them learn how to use the bottle, make sure the sipper is low enough for them to reach - they'll explore it sooner or later.  Your second litter can take their time weaning, though, as I think mice benefit from staying with their moms 4-5 weeks rather than being pulled out ASAP.

Also, just a heads up, your boys from the litters may fight as they grow up, since males don't usually get along.  If you can secure separate homes for them (or different cages), I would definitely recommend it.

Good luck with your new little ones!
-Tam