Grieving New Mom?

Question
About 3 months ago, I purchased my first
(white female) mouse as a pet. She started to seem lethargic, and uninterested in play time or much food/drink a few weeks later. I thought that maybe she was simply lonely since she had been with dozens of other mice. So, I purchased a 2nd(fancy brown female) a couple weeks later, the first female perked up and began enjoying life again. We soon discovered that the 2nd mouse was pregnant, and we worried about how the other female would behave around the babies. Not a problem. Both females were great care-takers, loving & maternal. About a week after the (12)babies were born, a black snake got into the house. It ate 3 babies and then the white female attacked it and ended up giving her life. We found the snake at that point got it out. Now, we have the brown female & 5 babies(1 female/4 males). Do you think the brown female is grieving over the lost white female or will the babies be enough to fill that void? Also, should I separate the males from the females to avoid more babies? Will they mate within their family like that, with their mother/sister?

Answer
I am so sorry you lost your mice, you are certainly a lot braver than I would be if I found a black snake in my house!

Perhaps your mouse is grieving in her own way, if not the companionship then certainly the help with the babies. She won't be lonely as you still have one female to keep her company once you separate the babies.

You should separate the males from the females at 4 1/2 weeks because the males will mate with both the females (mice are not as discerning as humans).

You can of course adopt more females and keep them with your existing girls, though I wouldn't get them from the same pet store!!

Please feel free to ask any more questions.