I always make sure my does know each other well before the due date. I take the doe away from the buck at 2 wks or earlier if she starts to show that she is pregnant and then I put her with a nanny straight away, it is usually a mouse she has been with prior to going to the buck. Sometimes you find the mum to be will not take to the nanny if put together for a short time before delivery and this could result in her culling her own litter as she feels the nanny to be a threat. It is best to put nanny with mum as soon as possible.
The nanny does not have to be pregnant also. I have found that if I have 2 does pregnant at the same time together that one of them gets run down and scrawny this is usually the doe who has fed the other does litter before she has had her own so she has had alot of pressure on her body to feed her own growing pups in side her as well as sustaining herself and feeding the new pups of another mouse, This is just what I find happens even though I feed my mice a good and hearty feed with added extras for pregnant and nursing does. Some people will say this doesnt happen to them but for me it does and for this reason I have since not put 2 pregnant does together incase it happens and I lose one of my does, but I put a mouse without pups in and if I remember she doesnt have to of had a litter to produce milk. Hope this helps you
As I am trying to reproduce the Banded mice I tend to keep pregnant mice littering alone as opposed to 2 littering together so I can check on who makes the best pups, so as a rule I usually bung in a near ready to breed doe ( 10 weeks ) with the preggers mouse to act as nanny which also then tells me if the nanny would make a good mother herself, she also gains pup experience and is less likely to reject her own litter.
Nannies are removed from the litters after about 20 days to be placed in for breeding themselves.
The odd thing with Banded I have found is they don't seem to like other breeds of mice unless introduced at a young age.
I have had pregnant mice retain their babies for longer than they should but then drop them when I remove the unrelated breed nanny, so it seems they do infact prefer to be with their own kind..........racist???
But then Banded mice often tend to be more aggresive towards other mice in general....moody buggers lol.
Great with people though, never had a problem with them.