I prefer to seperate them from the rest when they are noticably huge and ready to drop (you can almost see the individual lumplings at that point). Whenever possible I keep them seperate for raising the litters as otherwise I've observed they kind of continually juggle around "ownership". THe last batch I had to do this until I could get an extra cage - and as I went to seperate them I noticed one mother was nursing 2 pups while the other had hoarded 20, was noticably thin and feared the babies wouldt be getting enough milk. When they keep playing tag and snatching them from each otehr the pups can wind up with some scarring from being carried around in mom's mouth so often. Nothing detrimental ever came of this, none died or became sick etc, and the nursing mothers never seemed to squabble over it - still i felt better knowing all the pups were getting good suckle instead of 20 fighting for 8 nipples.


I never leave the mother/litters in with other non-preg or male rats as the few times this had (unintentionally) happened they disappeared pretty fast

Hopefully someone with longer experience than me can chime in here.