i have added females into my colonies with no real problems. Maybe a bit of excited chasing about and good once over from the others is usually what happens.

I added a new female to a 1.2 colony a week ago whilst one of the females was heavily pregnant..on saturday i got the lovely surprise of witnessing her helping my pregnant rat during Labour. It was nice to see as i have never seen an actual labour before and they all did there part. (apart from the male who just sat there asleep).

As for removing young , as it has already been said i would just try and observe after week 3 any signs of feeding and drinking on there own. Mine have all been roughly around 3 weeks to wean.

if there walking around its a matter of a few days befor ethe eyes open and id say a week after that to wean from what i have observed