Quite a few of our does have a cagemate (preferrably an older doe who has already had a litter or two). A few of our slow breeder bucks will stay with the doe and babies as they are aweseome about helping to raise the litter. I think its even better when it come to one of our pairs of does that always get pregnant together, they help each other deliver and raise and everything! I think having company is much less stressful that going solo.
I sometimes have the buck with two does, and they work very well together, sharing a nest and caring for the pinkies, especialy if the two does are sisters like with my Girlies #1 & #2. I won't even be wondering whose is whose since all the parents involved were orange and the litters were born about four days apart. It may be interesting to see what if any interesting recessives show up, though.
The first one gave birth and made a nest, and the second built her own nest for the birth, but the very next day the nests had been combined.
I dunno...I was taught that a pregnant doe needs to have her own nursery, perhaps with one friend who is not pregnant (This would be the nanny). I was also taught that nannies are ideal if they have never given birth themselves, that way they are willing to help Mom, but there is little danger of baby-theft since they've never had a litter of their own, they will have no desire to steal Mom's babies.
It is my opinion that it is dangerous to have more than one litter give birth in the same tank, jealousy, baby theft, and insecurity could cause a mother to cull her litter, or everyone's litter because she doesn't feel her babies are safe. It is also difficult to properly track lines if you don't know whose babies are whose.
Pregnant and nursing mothers need privacy to care for their young, if there are too many other does in the tank (even if they aren't preggo), it could turn out bad, the mother could become upset dealing with tank-hierarchy and cull her litter because she doesn't feel her babies are safe from the others. Personally, I would not allow a mother to give birth in a tank with more than one tankmate. I would give her an environment of her very own so she could set up the nest the way she wants, dig in, and have and raise those babies without any other influences to make her nervous.
I also wouldn't keep a male in, she could get pregnant again right away, and I wouldn't want her to try to nurse babies and deal with a back-to-back pregnancy at the same time, that could make her sick, and the second litter could be sickly, not enough milk and nutrients during gestation from a worn out body.
It depends entirely on the doe and the relationship she has with other does as to whether all those things you mentioned would happen.
Yes its a risk to have more than one doe litter in the same cage, but it is also a risk to have an inexperienced nanny too, and again, a risk to let a doe litter alone.
Nothing is sacred when breeding mice, they all have thier own personalities and temprements.
It is really up to the owner of said mice to do what they think is best.
Personally I keep my nursing does seperate - all of the mice I breed are dove self, and I like to know which babies came from which parents, because then I know who's producing the best mice. Also, the only time I tried having a nanny in there was with my first litter, and the nanny (who hadn't been bred before) kept stealing the babies, resulting in a tug of war over a buck. The kitten was thankfully unharmed and I took the nanny doe out. My single does always do really well, I haven't had a single problem with baby eating or anything, and the ladies always seem relaxed and happy even though they're alone.
However, I know of more people keeping pairs/groups of nursing does together with much success than I know of people that keep them singly like I do. I also know of many people who have success leaving the father in, although it's not something I do myself because I have no need to produce that many mice and I need my doves to be as big and healthy as possible for showing.
I find mice are very easy to please in general and will go along with your plans for them without complaint, so do what you feel is best
Right now I have a pregnant(well hopefully pregnant) doe in her cage along with her 2 daughters from her 1st litter. Neither one of her daughters is bred.
I think I will keep her in there with them until its closer to her due date then I will move her to her own cage.
Breeding and raising a healthy litter is never a sure thing no matter what kind of arrangement you make. Second guessing yourwelf either before the fact or after the fact is pointless. Sometimes it works this way other time it works that way. I'd be a lot more likely to let a doe who had already raised a litter have a private tank than I would with a first time mother.