If you ever have to move around 1-5 day old mice, I have found that it helps if rub some used mouse bedding from that enclosure in your hands before you pick anything up. Kinda gets rid of that 'human' smell and will prevent the mama from eating or abandoning a baby because they don't smell right.

With moving around babies and housing with males, you also want to make sure not to have another male mouses smell on your hands or seperate the babies and the father for too long. Male mice will kill the babies if they think that the babies are not theirs.

Mother mice do not seem to be all that picky with their babies. I have mixed up litters before and had no problems. They generally like to have their own nest instead of sharing one. If you have two females with young in the same enclosure, you may see them 'stealing' each others young.....this is fine and is actually funny to watch.

Mice are very interesting critters and are fun to watch sometimes. Hope that little bit of info that I have picked up along the way helps.....if not I have alot more