Thanks, Gin! Not only did Biscuit have her litter, but one of the other two females looks ready to burst and we suspect the other is pregnant too, as well as the mouse. Because we took out the males to give the girls a break, every one of our cages is occupied right now. At least once they're weaned, we should be able to put the babies from different litters together by sex until they're the right size to put down.