Sonya, thanks for the advice. Today I separated all of the young mice (except the pinkies) and noticed that there isn't a male in that cage. I think I have a 0.6 colony with 3 pregnant females. I attempted to add a male and he was immediately attacked by one of the females. Mayhem, just like you said.

So I guess I should put the pregnant females (that I pulled out) back in the 10 gallon aquarium. Every mouse in there has multiple teats. I don't see male reproductive organs on any of them. I guess I'll have to let them raise one up.

Another question: I also have (2) freedom breeder mouse levels (with 5 tubs each). This is where I placed the pregnant females as I was waiting for them to birth. What size colony could I set up in there? Or, should I use those tubs for growing out the 3.5-4.5 week mice that I separate?